1. No category

18-21 SEPTEMBER 2011
CHAMPALIMAUD
NEUROSCIENCE
SYMPOSIUM
ABSTRACT BOOK
2
FUNCTIONAL CONSEQUENCES OF DIFFERENT FORMS OF SPIKE-TIMING DEPENDENT
PLASTICITY
Larry Abbott
Columbia University, USA
Like long-term potentiation, spike-timing dependent synaptic plasticity (STDP) is not a
single phenomenon with a unique description, but appears to take a variety of forms.
In particular, experimental and theoretical work have suggested different types of
interactions between multiple pairs of pre- and postsynaptic spikes that induce STDP.
Baktash Babadi, a former Columbia graduate student and current postdoc at Harvard,
and I have analyzed a number of STDP models to determine their stability properties
and the forms of competition (Hebbian, anti-Hebbian) they generate. We have also
used a analysis of STDP between cell pairs to understand network effects of this form
of plasticity. I will present these results.
SPEAKERS
3
ORGANIZATIONAL PRINCIPLES OF ANTAGONISTIC MOTOR CIRCUITS
Silvia Arber
Biozentrum and FMI, Basel, Switzerland
Motor behavior represents the ultimate output of most nervous system activity. The
organization and function of the mature nervous system relies on the precision with
which defined neuronal circuits assemble into functional units during development. In
the spinal cord, connections to motor neurons are formed by many distinct interneuron
classes, by neurons with descending projections from higher brain centers, and by
proprioceptive sensory neurons, providing feedback from the periphery to coordinate
motor output. This talk will focus on recent progress in understanding the
organizational principles of neuronal circuits in the spinal cord, with an emphasis on
circuits regulating motor antagonism.
4
DUPLICATION AND DIVERGENCE OF NEURAL CIRCUITS IN BILATERIAN BRAIN
EVOLUTION
Detlev Arendt
Developmental Biology Unit European Molecular Biology Laboratory, Germany
The step-wise diversification of neuron types is assumed to trigger the evolution of
neural circuits, following the “division of labour” model. The model proposes that
diversifying neuron types specialize on distinct functions (sensory, interneuron, motor)
but maintain information exchange via cellular extensions that evolve into axonal
connections. During evolution, more neuron types are intercalated into the circuit and
take over different relay functions. Moreover, circuits can split and diverge at any level,
specializing on different sensory modalities, different modes of information integration,
or motor output. To evaluate these models, and to track the evolution of neuron types
and of neural circuits, we need to know, for as many neurons as possible in a
differentiating brain, their molecular identity (to detect related neuron types) together
with their axonal projections (to find out how they assemble into circuits). To this end,
we are building a unique resource, the Platynereis Neuron Type Atlas, combining, for
the first time, neuronal morphologies, axonal projections and cellular expression
profiling for an entire bilaterian brain. Our aim is to elucidate the evolution of the
complex circuitry of the vertebrate and insect forebrain by comparison to the much
simpler “connectome” of a marine annelid that has retained ancestral characteristics of
the urbilaterian brain.
HOW ACTIVITY CHANGES SYNAPSES IN THE MAMMALIAN BRAIN
Tobias Bonhoeffer
Department of Cellular and Systems Neurobiology, Max-Planck-Institute of
Neurobiology, München-Martinsried,Germany
One of the most fundamental properties of the brain is its ability to adapt rapidly to
environmental changes. This is achieved mainly by changes in the connectivity
between individual nerve cells. Synapses can be modulated in their strength by a
variety of different mechanisms. We have investigated a number of these mechanisms,
ranging from homeostatic control of synaptic efficacy to morphological manifestations
of synaptic strengthening or weakening, and the role of calcium in these processes.
Yet, while we are beginning to understand the cellular mechanisms underlying synaptic
changes, it is important to consider the functional implications of synaptic plasticity in
the intact brain. We are therefore applying new imaging methods to investigate the
effects of experience on synaptic changes in cortical circuits. In particular, in vivo twophoton microscopy has enabled us to study morphological as well as functional
plasticity at the level of individual neurons in the neocortex of anesthetized and lately
also behaving animals. These experiments are beginning to close the gap between
traditional cellular and systems studies, and they will enable us to obtain a much more
comprehensive understanding of the phenomenon of synaptic plasticity and its role in
cortical function and ultimately behavior.
5
NEURAL SYNTAX: SEGMENTATION OF INFORMATION IN THE HIPPOCAMPUS
Gyorgy Buzsaki
Board of Governors Professor, Center for Molecular and Behavioral Neuroscience,
Rutgers University, NJ, USA
The dominant theoretical form of mental structure of the last century was implicitly a
neuropsychological model. At the center of this model, necessary for episodic free
recall, planning or logical reasoning, is Hebb’s phase sequences of neuronal
assemblies, i.e., hypothetical self-propagating loops of neuronal coalitions connected
by modifiable synapses. These phase sequences can be activated by exogenous or
endogenous (internal) sources of stimulation, independent from environmental
determinants of behavior. The neurophysiological implication of this conjecture for
episodic recall is that hippocampal networks are endowed by an internal mechanism
that can generate a perpetually changing neuronal activity even in the absence of
environmental inputs. Recall of similar episodes would generate similar cell assembly
sequences, and uniquely different sequence patterns would reflect different episodes.
Using large-scale recording of neuronal ensembles in the behaving rat, I will show
experimental support of self-perpetuating activity neuronal assemblies and
demonstrate how oscillations support precise spike timing across neuronal populations.
The physiological characteristics of these assemblies are virtually identical to features
of hippocampal place cells controlled by environmental and/or idiothetic stimuli. I
hypothesize that neuronal mechanisms introduced for navigation in the physical
environment in “simpler” animals are identical to those needed for memory recall
and/or planning animals with larger brains. The different appearance of
representations in the hippocampus of different species and different segments of the
hippocampus in the same species may reflect its functional connectivity with the
neocortex and other structures.
References:
Buzsaki, G. and Draguhn, A. Neuronal oscillations in cortical networks. Science 304:
1926-1929, 2004.
Buzsaki G. Rhythms of the Brain. Oxford University Press, 2007
E. Pastalkova, V. Itskov, A. Amarasingham, and G. Buzsáki. Internally generated cell
assembly sequences in the rat hippocampus. Science 321, 5894:1322-7, 2008.
Buzsaki G. Neural syntax: cell assemblies, synapsembles, and readers. Neuron 68:36285, 2010.
6
THE BALANCE OF INHIBITION TO EXCITATION REGULATES VISUAL RESPONSES AND
BEHAVIOR IN VIVO
Hollis T. Cline
The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA, USA
The balance of inhibitory to excitatory synaptic inputs is thought to control information
processing and behavioral output of the CNS, however, no study has determined the
effects of altered inhibition/excitation (I/E) ratio on circuit function and behavior. We
used the visual system in Xenopus to probe the postulated function of I/E in brain
function. Synaptic inhibition was decreased with a peptide called ICL, which interferes
with synaptic anchoring of GABAAR, or by knocking down the GABAAR !2 subunit.
Both ICL and !2-knockdown decrease in the frequency of mIPSCs, without affecting
mEPSC frequency, resulting in a ~50% decrease in I/E. We recorded visually-evoked
responses from optic tectal neurons in intact Xenopus tadpoles in which the synaptic
I/E was decreased. Decreasing I/E increases the variance of first spike latency of visual
responses, increases recurrent activity in the tectum, increases spatial and temporal
receptive field size and disrupts input/output relations. Diazepam increases I/E ratio by
~30% compared to control neurons. Diazepan delayed first spike latency, increased
temporal precision and decreased receptive field size. Finally, a tectally-mediated visual
avoidance behavior is blocked in tadpoles with decreased or increased I/E. These
studies demonstrate that disrupting I/E interferes with visual information processing
and visually-guided behavior.
FEELING AND SENTIENCE: TAKING STOCK
Antonio Damasio
University Professor, David Dornsife Professor of Neuroscience, Director - Brain and
Creativity Institute, University of Southern California, USA
Antonio Damasio is a neurologist and neuroscientist. He is University Professor, David
Dornsife Professor of Neuroscience, and Director of the Brain and Creativity Institute at
the University of Southern California, in Los Angeles. He is the author of several
hundred scientific articles and the recipient of many prestigious awards including the
2010 Honda Prize; the 2005 Prince of Asturias Prize in Science and Technology; and
the Pessoa and Signoret Prizes, shared with his wife Hanna Damasio (who is also a
neurologist and neuroscientist, and is the Dana Dornsife Professor of Neuroscience and
Director of USC’s Dornsife Brain Imaging Center). Damasio is a member of the
Institute of Medicine of the National Academy of Sciences and a Fellow of the American
Academy of Arts and Sciences, the Bavarian Academy of Sciences, and the European
Academy of Sciences and Arts. He holds Honorary Doctorates from several Universities.
His most recent book is Self Comes to Mind, (published in 2010.) His other books
include Descartes’ Error, The Feeling of What Happens, and Looking for Spinoza, which
have been translated into over 30 languages and are taught in universities worldwide.
(For more information go to the Brain and Creativity Institute website at
http://www.usc.edu/bci/
and
the
Dornsife
Imaging
Center
website
at
http://brainimaging.usc.edu)
7
DISSECTION OF NEOCORTICAL MICROCIRCUIT
Yang Dan
University of California, Berkeley, USA
I will discuss two lines of research on cortical microcircuit. Using optogenetic
manipulations, we found that different subtypes of inhibitory interneurons have distinct
effects in shaping the visual response properties of cortical neurons. Intracellular
recording and stimulation combined with two-photon imaging allowed us to map the
functional connectivity between excitatory neurons and different types of inhibitory
interneurons.
WHAT NEURONAL ALGORITHMS UNDERLIE VISUAL OBJECT RECOGNITION?
James J. DiCarlo
Associate Professor of Neuroscience, McGovern Institute for Brain Research and
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology,
Cambridge, USA
Visual object recognition is a fundamental building block of memory and cognition, and
a central unsolved problem in systems neuroscience, human psychophysics, and
computer vision. Our research synergizes these three research fields to attack the
central challenge of object recognition. The computational crux of object recognition
problem is that the recognition system must somehow tolerate tremendous image
variation produced by different views of each object -- the so-called, “invariance
problem.” We have previously shown that the highest level of the ventral visual
stream (inferior temporal cortex, IT) conveys neuronal population codes that
qualitatively solve the invariance problem.
Are such codes are quantitatively sufficient to explain human performance? If so, how
they are constructed by ventral stream cortical algorithms? Here, I will highlight recent
progress on both questions. First, I will outline how systems neuroscience combined
with human psychophysics reveals that some IT population codes are nearly sufficient
to explain human performance on invariant object recognition. Second, I will show
that the ventral stream uses temporal contiguity cues from the natural visual
environment to “learn” to build these powerful IT codes. Novel computer vision
technology is now leveraging such results to guide us toward discovery of the
underlying cortical algorithms.
8
VISUAL NAVIGATION IN DROSOPHILA
Michael Dickinson
Ben Hall Professor of Life Sciences, Dept. of Biology, University of Washington, USA
One of the greatest challenges in neurobiology is in understanding how nervous
systems can generate long seamless sequences of behavior, for example, the yearly
migrations of birds, whales, or insects from the poles to the tropics. The research in
my laboratory focuses on the flight behavior of fruit flies which - although not global
migrants - do use flight to disperse over long distances and explore their local
environment for food and mates. A successful flight sequence from take-off to landing
involves many sensory-motor programs operating in series and parallel on different
time scales. By applying various quantitative behavioral methods we are attempting to
identify and isolate these different sensory-motor modules at the algorithmic level, with
the ultimate goal of identifying the underlying circuits. My talk will focus on several
critical visually-mediated components of flight behavior including take-off, navigation,
predator avoidance, and landing.
THE COMPUTATIONAL LOGICS OF NETWORKS IN MOTION - FROM ION CHANNELS
TO BEHAVIOUR
Sten Grillner
Nobel Institute for Neurophysiology, Karolinska Institutet, Stockholm, Sweden
The vertebrate brain controls a great variety of movements through dedicated
networks like those controlling eye movements, expression of emotions, respirations
and locomotion. These networks are to a large degree conserved through a vertebrate
phylum. The neural mechanisms underlying the control of goal directed locomotion will
be in focus. The propulsive locomotor synergy is controlled from command regions in
mesencephalon, which in turn control central pattern generating (CPG) networks in the
spinal cord. My presentation, based on the lamprey CNS, will address the intrinsic
function of the adaptable CPG that can generate different motor patterns. In addition,
I will discuss the tectal mechanisms underlying steering movements with the
retinotopic motor map, and the control from the output of the lamprey basal ganglia.
Furthermore, the mechanism by which different motor programs are selected will be
considered with special reference to the basal ganglia – experiments and modelling.
Our recent findings establish that the structure and function of the basal ganglia have
been conserved to a surprising degree from the ancient lamprey version to primates.
This applies to the input to striatum (pallium, thalamus, dopamine, 5-HT, histamine
input), the pallidal structures (GPi, substantia nigra reticulate (SNr), GPe and the
subthalamic nucleus) and their output targets, the cellular properties of striatal and
pallidal neurons and the effects of an MPTP induced dopamine denervation.
References:
Kozlov A, Huss M. Lansner A, Hellgren Kotaleski J, Grillner S. (2009) Simple cellular and
network control principles govern complex patterns of motor behavior. PNAS
24;106:20027-20032.
Grillner, S. (2006) Biological Pattern Generation: The Cellular and Computtional Logic
of Networks in Motion. Neuron 52; 751-766
9
DENDRITIC COMPUTATION
Michael Hausser
University College London, UK
The computational power of dendrites has long been predicted using modelling
approaches, but actual experimental examples of how dendrites solve computational
problems are rare.
I will describe results from experiments combining patch-clamp recordings with two
photon imaging and glutamate uncaging that demonstrate how single dendrites in the
mammalian brain can act as fundamental units of information processing.
References:
London, M. & Häusser, M. (2005). Dendritic Computation. Annual Review of
Neuroscience 28, 503-532.
Branco, T., Häusser, M. (2010). The single dendritic branch as a fundamental
functional unit in the nervous system. Current Opinion in Neurobiology, 20(4):494-502.
SOCIAL EXPERIENCES AFFECT ETHANOL INTAKE IN DROSOPHILA THROUGH
NEUROPEPTIDE F
Ulrike Heberlein
University of California San Francisco, USA
Natural reward systems serve to reinforce behaviors required for the survival of
individuals and species, such as sexual activity, food consumption, nursing, social
interaction, and play. Alcohol and other drugs of abuse co-opt neural pathways
associated with natural rewards. Our goal was to establish mechanistic links between
social experience, reward, and drug self-administration in the genetically tractable
model organism Drosophila melanogaster. We show that social experience affects
voluntary ethanol consumption in Drosophila, and that neuropeptide F (NPF, the fly
homolog of neuropeptide Y) serves as a key molecular transducer. Chronic sexual
rejection reduces NPF levels in males, while mating increases NPF levels. Activation of
the NPF circuit negatively regulates ethanol consumption, such that low NPF levels lead
to enhanced ethanol preference in rejected males, and high NPF levels lead to
decreased ethanol preference in mated males. We propose that sexual experience
regulates ethanol consumption by affecting the state of the reward system: a state of
reward deficit (sexual rejection) enhances ethanol consumption, whereas a rewarding
experience (mating) has the opposite effect. Drosophila is therefore a genetically
accessible model system to study the mechanisms by which social experience
modulates reward-related behaviors.
LOSS OF CROSS-MODAL CORTICAL ACTIVITY BY VISION
Takao Hensch
Harvard University, Center for Brain Science, Children's Hospital Boston, USA
Early blind subjects reliably process tactile or sound stimuli in visual cortex, which is
associated with superior discrimination. Here, we show in a mouse model that this
results from a failure to lose early ectopic input rather than acquisition of novel crossmodal connections. Vision during a late critical period normally drives the removal of
both cortico-cortical and thalamo-cortical auditory projections. Nogo receptor (NgR1)
signaling is required to shape the typical unimodal response in visual cortex. Retention
of cross-modal input in early visually-deprived or NgR1-deficient mice preferentially
enhances the potentiating influence of multi-sensory integration.
10
INHIBITORY CIRCUITS FOR VISUAL PROCESSING IN THALAMUS
Judith Hirsch
Department of Biological Sciences & Neuroscience Graduate Program, University of
Southern California, Los Angeles, CA USA
It was once thought the visual thalamus simply acted as a gatekeeper for the cortex,
relaying retinal signals during waking but preventing their passage during sleep.
However, it has become increasingly clear that the thalamus plays an active role in
sensory integration. Thalamic processing is dominated by two separate inhibitory
pathways. One provides feedforward inhibition; it is formed by interneurons within the
lateral geniculate nucleus. The other, supplied by the thalamic reticular nucleus,
generates feedback inhibition. Both circuits converge onto the relay cells that project
to cortex.
We explored thalamic inhibition from the dual perspectives of systems physiology and
information theory, using experimental approaches of intracellular and extracellular
recording in vivo combined with anatomy. Our results suggest that feedforward
inhibition serves diverse roles in neural computation.
It complements retinal
processing to expand the dynamic range of response, enhances selectivity for stimulus
features in space and time and improves the efficiency of the neural code. It is so
powerful that it can drive neural firing from tonic to burst modes. Moreover, we found
that relay cells and local interneurons each have unique patterns of synaptic
integration that work in concert to optimize the rate of information transmitted
downstream. Our complementary studies of the reticular nucleus suggest that
feedback inhibition is engaged by first and higher order features of the stimulus and is
designed to modulate the activity of relay cells over local spatial scales. Because the
structure of the visual thalamus is similar to that of other sensory thalamic nuclei, our
results likely illustrate basic principles of thalamic function.
MOTOR CIRCUITS AND THE SENSE OF PLACE
Tom Jessell
HHMI, Columbia University, USA
The formation of synaptic connections is a defining moment in the assembly of neural
circuits, providing a structural foundation for network activities that govern the
subtleties of animal behavior. In the mammalian spinal cord sensory-motor circuits are
constructed with a fine specificity that ensures coordinated motor behavior, although
the cellular strategies and molecular mechanisms that direct sensory connections with
functionally relevant motor neuron partners remain unclear. The dorso-ventral settling
position of motor pools in the spinal cord has long been known to match the distal-toproximal position of their muscle targets in the limb, although the significance of this
topographic register is obscure. Our analysis of sensory-motor connectivity patterns in
mouse mutants in which motor neuron position has been scrambled shows that key
features of sensory-motor connectivity are established through the ability of the axons
of proprioceptive sensory afferents to project to, and terminate in, discrete dorsoventral tiers within the ventral spinal cord in a manner that is independent of target
motor neuron subtype. By implication, the positional organization of motor neurons
along the dorso-ventral axis of the spinal cord appears to be a critical early step in the
establishment of sensory input specificity.
11
SYNAPSE TO NUCLEAR TRANSPORT OF A TRANSCRIPTIONAL REGULATOR DURING
NEURONAL PLASTICITY
Kelsey Martin
Department of Biological Chemistry, UCLA, USA
Long-lasting changes in synaptic efficacy, such as those underlying long-term memory,
require transcription. Activity-dependent transport of synaptically localized
transcriptional regulators provides a direct means of coupling synaptic stimulation with
changes in transcription. The CREB-Regulated Transcriptional Coactivator (CRTC1)
binds CREB to potently promote CRE-driven gene expression, and is required for longterm hippocampal plasticity. We show that CRTC1 localizes to synapses in silenced
hippocampal neurons, but undergoes rapid, dynein-mediated, microtubule-dependent,
active nuclear transport to the nucleus in response to synaptic stimulation. Regulated
nuclear translocation occurs only in excitatory neurons, and requires calcium influx and
calcineurin activation. CRTC1 is controlled in a dual fashion with activity regulating the
amount of CRTC1 translocated to the nucleus and cAMP modulating its persistence.
Neuronal activity triggers a complex change of CRTC1 phosphorylation, suggesting that
CRTC1 may link specific types of synaptic activity to specific changes in gene
expression. Together, our results indicate that synapse to nuclear transport of CRTC1
functions to dynamically inform the nucleus about synaptic activity.
NEW FLUORESCENT PROBES AND NEW PERSPECTIVES IN BIOSCIENCE
Atsushi Miyawaki
Laboratory Head, RIKEN BSI/Project Director, JST ERATO, Japan
In the nervous system, intracellular signaling events are closely linked with electrical
activities, and play essential roles in information processing. To identify and
characterize the mechanisms by which signals are organized inside cells, it is necessary
to analyze spatiotemporal patterns of signaling pathways. On the other hand, neural
circuitry operates as an ensemble in the nervous system. To investigate the patterns of
neuronal firing, it is necessary to monitor multiple transmembrane voltages or signals
that result from electrical activity in complex tissues or intact animals. Over the past
decade, various probes have been generated principally using fluorescent proteins. I
will discuss how the probes have advanced our understanding of the spatio-temporal
regulation of biological functions inside neurons and brains, and their technical
limitations. I will speculate on how these approaches will continue to improve due to
the various features of fluorescent proteins. Finally, I will discuss in-depth brain
imaging, which is one of the most sought-after themes of today’s optical technologies,
as my laboratory has been and will be engaged in the development of new
technologies that would advance the imaging depth limit
12
GABAERGIC INTERNEURONS AND THEIR ROLE IN NEURONAL SYNCHRONIZATION,
LEARNING AND MEMORY
Hannah Monyer
Medical Faculty of Heidelberg University and German Cancer Research Institute
Heidelberg, Germany
Rhythmic inhibition provided by GABAergic interneurons modulates the firing of
pyramidal cells, but its contribution to both rate and temporal coding by hippocampal
pyramidal cells has not been studied so far. I will present studies in which we took
recourse to cell type-specific genetic modifications altering the activity of fast spiking
interneurons. We interfered with the recruitment of interneurons by ablating either
ionotropic studied glutamate receptors or gap junction coupling. We studied the effect
of the genetic manipulations on two different types of spatial memory processes,
namely long- and short-term spatial learning. To gain more insight into potential links
between physiological processes and the behavioral phenotype, we performed in vivo
recordings in freely moving mice focusing on characteristics of hippocampal-entorhinal
cortex activity supporting spatial and temporal coding. Finally, I will present molecular
approaches to study GABAergic interneuron connectivity in hippocampal-entorhinal
networks.
BELIEVING AND TIME: A NEURAL MECHANISM FOR DECISION MAKING
Michael N. Shadlen
Professor of Physiology & Biophysics; Investigator, Howard Hughes Medical Institute,
University of Washington Medical School, USA
This lecture describes recent advances in our understanding of the neural mechanisms
responsible for some forms of decision-making. The study of decision-making opens a
window on the neural basis of many other higher cognitive capacities which also use
information in a contingent fashion and in a flexible time frame — free from the
immediacy of sensory events or the need to control a body in real time. I will describe
neural recordings from the parietal cortex of nonhuman primates that are trained to
make difficult perceptual decisions.
The neural responses provide insight into how decisions are made: how accuracy and
speed are traded against one another, how the brain reasons from probabilistic cues
(as in predicting the weather), how prior probability affects the decision process, and
how the brain assigns confidence — degree of belief — that a decision is correct. I plan
to focus on this last topic in this short talk, but I lack confidence in this decision.
SYNAPTIC MECHANISMS OF SENSORY PERCEPTION
Carl Petersen
Ecole Polytechnique Federale de Lausanne (EPFL)
A key goal of modern neuroscience is to understand the neural circuits and synaptic
mechanisms underlying sensory perception. Here, I will discuss our efforts to
characterise sensory processing in the mouse barrel cortex, a brain region known to
process tactile information relating to the whiskers on the snout. Each whisker is
individually represented in the primary somatosensory neocortex by an anatomical unit
termed a ‘barrel’. The barrels are arranged in a stereotypical map, which allows
recordings and manipulations to be targeted with remarkable precision. In this cortical
region it may therefore be feasible to gain a quantitative understanding of neocortical
function. We have begun experiments towards this goal using whole-cell recordings,
voltage-sensitive dye imaging, viral manipulations, optogenetics and two-photon
microscopy. Through combining these techniques with behavioral training, our
experiments provide new insight into sensory perception at the level of individual
neurons and their synaptic connections.
RELEASING THE BRAKE ON SYNAPTIC PLASTICITY
Carla J. Shatz
Professor of Biology and Neurobiology; Director of BioX, Stanford University, USA
Connections in adult visual system are highly precise, but they do not start out that
way. Precision emerges during critical periods of development as synaptic connections
remodel, a process requiring neural activity and involving regression of some synapses
and strengthening and stabilization of others. We discovered unexpectedly that MHC
Class I genes and an innate immune receptor, PirB, are involved in this process. In
mice lacking expression of specific MHCI proteins, synapse regression in developing
visual system fails to occur, synaptic strengthening is greater than normal in adult
hippocampus, and ocular dominance (OD) plasticity in visual cortex is enhanced.
Plasticity in mutant mice lacking PirB is also enhanced. Thus, MHCI ligands signaling
via PirB receptor may function to “brake” activity- dependent synaptic plasticity.
Together, results imply that these molecules, thought previously to function only in the
immune system, also act at neuronal synapses to limit how much- or perhaps how
rapidly- synapse strength changes in response to new experience. Changes in the
function of these molecules may also contribute to developmental disorders such as
Autism and Schizophrenia.
13
14
MOLECULAR AND CELLULAR MECHANISMS OF MEMORY ALLOCATION IN NEURONAL
NETWORKS
Alcino J Silva
Department of Neurobiology, Department of Psychology, Department of Psychiatry,
Integrative Center for Learning and Memory, Semel Institute, Brain Research Institute,
University of California, Los Angeles, California, USA
Although memory allocation is a subject of active research in computer science, little is
known about how the brain allocates information within neural circuits. Recent findings
from our laboratory suggest that memory allocation is not random, but rather specific
mechanisms regulate in which cells information is stored within a neural circuit. We
used a range of single cell manipulation and recording techniques to demonstrate that
CREB activity regulates neuronal excitability and consequently the allocation of fear
memory to specific cells in lateral amygdala. Our studies also suggest that some of the
mechanisms involved in the consolidation of one memory (e.g., CREB activation) for a
time affect the allocation of the next memory.
NEURAL CODES: THE CURSES AND BLESSINGS OF HIGH DIMENSIONS
Haim Sompolinsky
Interdisciplinary Center for Neural Computation, Edmond and Lily Safra Center for
Brain Sciences, Hebrew University, Jerusalem, Israel
Neuronal circuits must cope with the challenges of processing, interpreting, and
communicating complex high dimensional sensory as well as neuronal signals. Various
theories of dimensionality and redundancy reductions have been proposed as
strategies for fighting the curse of dimensionality. However, in many settings,
dimensionality expansion, in particular in the form of redundant sparse coding, has
clear computational advantages.
In my talk I will review some advances in high dimensional signal processing, in
particular Compressed Sensing, which shed new light and provide a unified framework
for understanding compression, expansion, and sparse coding in neuronal systems. I
will discuss potential applications in the areas of sensory processing, learning and
memory.
The talk is based on joint work with Surya Ganguli.
15
SPECIALIZED ODORS THAT GENERATE INNATE BEHAVIOR
Lisa Stowers
The Scripps Research Institute, USA
We are studying how subsets of neurons specify behavior. Pheromone ligands activate
dedicated subsets of neurons to generate instinctive behavior which provides a
powerful experimental system to study neural function. Our approach is unique in that
we have developed quantifiable analysis of the mouse’s natural behavior. As
biochemical assays are used to map and elucidate metabolic pathways, we use innate
behavior as a functional assay to identify the corresponding ligand cues and cognate
neurons that generate behavior. We are directing our experiments to identify
underlying neural mechanisms that encode behavior using molecular probes, genetic
manipulation, and functional imaging. We expect that restricting our investigation to a
single behavior will enable us to identify the neural code for that behavior. Ultimately,
however, that approach would limit our ability to define the unique neural features of
one behavior from the common mechanisms of all behavior promoting circuits.
Therefore, we are identifying the ligands that direct four different innate behaviors in
order to clearly define general neural principles. These behaviors include aggression,
fear, mating, and pup-suckling. We expect this focused multi-circuit strategy to
advance our understanding of the neural principles that generate behavior.
HUMAN SWEAT AND INSECT REPELLENTS: THE MOLECULAR BIOLOGY OF MOSQUITO
OLFACTION
Leslie B. Vosshall
HHMI Investigator; Robin Chemers Neustein Professor, The Rockefeller University, New
York, NY, USA
Olfactory cues guide mosquitoes toward humans, from which the mosquitoes derive
the blood they need to complete ovarian development. In carrying out this innate
behavior, mosquitoes spread dangerous infectious diseases such as malaria, dengue
fever, and yellow fever. My group is interested in the molecular neurobiology of
mosquito host-seeking behavior. Human body odor is a long-range, attractive cue that
guides mosquitoes to their hosts. The mosquito perceives differences in body odor,
both between and within species, to determine which animal or human to target for
blood-feeding. To shed new light on mosquito olfaction and host-seeking behavior, we
are taking a multi-disciplinary approach that combines molecular genetics, genomics,
and behavior. We have developed a technique for targeted mutagenesis in the yellow
fever and dengue vector mosquito, Aedes aegypti, using zinc-finger nucleases. The
establishment of loss-of-function genetics in Aedes aegypti opens new paths of
investigation in vector biology including the neurobiology of host-seeking. We have
identified a candidate neuropeptide receptor that may regulate the suppression of
host-seeking behavior that is known to be induced by and last for about 72 hours after
the mosquito takes a blood meal. We are also developing novel mosquito repellents
using target-based approaches to screen for small molecules that interfere with the
molecular odorant receptors of insects. This presentation will discuss recent advances
in the molecular biology of smell in mosquitoes.
16
PROBABILISTIC MODELS OF HUMAN SENSORIMOTOR CONTROL
Daniel Wolpert
Department of Engineering, University of Cambridge, UK
The effortless ease with which humans move our arms, our eyes, even our lips when
we speak masks the true complexity of the control processes involved. This is evident
when we try to build machines to perform human control tasks. While computers can
now beat grandmasters at chess, no computer can yet control a robot to manipulate a
chess piece with the dexterity of a six-year-old child. I will review our recent work on
how the humans learn to make skilled movements covering probabilistic models of
learning, including Bayesian and structural learning, and the interaction between
decision making and sensorimotor control.
POSTERS
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18
SPIKE-BASED SOUND RECOGNITION USING NEUROMORPHIC VLSI HARDWARE
Mohammad Abdollahi, Fabio Stefanini, Shih-Chii Liu and Giacomo Indiveri
Institute of Neuroinformatics, ETH Zurich and University of Zurich
We are implementing spike-based models of sound recognition using neuromorphic
VLSI technology. Our goal is to develop a hardware sound recognition system which is
based on continuous time, stimulus-driven, asynchronous, distributed, collective, and
self- organizing principles. The front-end of this system is implemented using an eventbased silicon cochlea, while the output stage will be implemented using a multi-neuron
chip with spike-based learning properties. The processing of auditory signals at the
intermediate computational stages will be implemented using state-of-the-art spiking
neural models, based on Spike-Timing Dependent Plasticity (STDP) learning methods
and exploiting the dynamics of recurrent networks of neurons.
In order to compare these neurally inspired algorithms to the state-of-the-art methods
used in speech recognition, and to evaluate the discriminative information present in
the signals extracted by the silicon cochlea we carried out speaker-independent
isolated digit recognition experiments. The results show promising recognition
accuracies over large number of different speakers from TIDIGITS database: the
discriminative information in spike patterns is sufficient for a task as complex as
speaker-independent isolated keyword recognition even in adverse environmental
conditions.
CHRONIC TOXOPLASMA INFECTION MODIFIES THE STRUCTURE OF HOST BEHAVIOR
THE ADAPTIVE VALUE OF BEHAVIOUR AND ITS UNDERLYING GENETIC STRUCTURE
Bruno Afonso (1,2) Christine Goy (1), Henrique Teotónio (1) and Rui M. Costa (2)
(1) Instituto Gulbenkian de Ciência, Oeiras, Portugal; (2) Champalimaud Centre for the
Unknown, Lisbon, Portugal
This project aims to reach a genetic structure of behaviour and assess its adaptive
value. To that purpose, I am using the worm Caenorhabditiselegans as a model
organism because of its rich behaviour repertoire, short generation time and widely
described brain connectivity. I have derived 100 recombinant inbred lines from
an outbred population that has previously adapted to a laboratory environment. These
lines will be sequenced genome-wide and assayed for a behavioural phenotype such as
locomotion and mate approach and offspring yield. From this information, I will obtain
the genes responsible for the phenotypes, which will be analysed further in a functional
perspective and, later on, in an evolutionary perspective, using an experimental
evolution approach.
DETAILED VISUALIZATION AND MORPHOMETRIC ANALYSIS OF RECONSTRUCTED
NEURONS USING BLENDER AND PYTHON
Aguiar P (1), Szucs P (2)
(1) Centro de Matematica da Universidade do Porto, Portugal; (2) Spinal Neuronal
Networks, Instituto de Biologia Molecular e Celular, Portugal
Topology and functional features are two related aspects in a neuron. Understanding
and measuring the neuron's topology is therefore an important step in inferring its
functional properties. Unfortunately the sheer complexity of most neuron's structures
makes it virtually impossible to describe the topology richness in just a handful of
parameters. Ultimately, the best way to describe a neuron's topology is by plainly
performing reconstruction and visualizing it in a virtual 3D space. Here we present a
collection of scripts, written in python programming language, which use Blender for
3D visualization. Blender is a well established free open-source 3D content creation
suite, available for all major operating systems under the GNU General Public License.
The main script is able to read the ASC file format from Neurolucida (MicroBrightField,
Inc.), the most commonly used system for single neuron reconstruction. The script's
GUI offers several options including interpolation in trees. A library of python functions
were also created providing measurements and calculations on the parsed neuron
data. These functions are accessible through an interactive python command window
and they allow, among other things, calculation of varicosities densities, fibre lengths
and inter-spine distances. The library can easily be extended to incorporate new
functions.
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20
Cristina Afonso, Vitor B. Paixão and Rui M. Costa
Champalimaud Neuroscience Programme at Instituto Gulbenkian de Ciência
Toxoplasma gondii parasite has an indirect life cycle, with felines as definitive hosts. It
has been suggested that this parasite developed mechanisms for enhancing its
transmission to felines by inducing behavioral modifications in the intermediate rodent
host. We analyzed infected C57Bl/6J mice brains and detected parasite cysts
distributed non-randomly. We demonstrate that Toxoplasma chronic infection is able to
modify particular aspects of hardwired innate behaviors, such as exploration and
defensive behaviors in the open field and elevated plus maze tests. Chronically infected
animals show high locomotion speed, which enables mice to cover longer distances,
and also a change in initial behavior when encountering a novel environment. We also
uncovered a consistent modification in the organization and structure of exploratory
locomotion in infected mice involving a change from frequent, short bouts to longer
bouts. Our studies also report a differential behavioral response to safe vs unsafe
areas, detected in infected animals, indicating a loss of the usual bias towards cautious
behavior. This is likely to reflect inefficient risk assessment strategies, preventing
infected animals from correctly displaying an adequate defensive response and
promoting the engagement in risky behavior, all of which could potentially enhance
predation/capture rates.
RESPONSE DYNAMICS OF GAMMA OSCILLATING CA3 NETWORKS.
Thomas Akam, Emily Ferenczi, Laura Mantoan, Dimitri Kullmann
Experimental Epilepsy Group, UCL Institute of Neurology, London, UK
Gamma frequency oscillations occur in many neural circuits and exhibit dynamically
changing patterns of local circuit and inter-region synchronisation, often correlated
with behavioural or cognitive tasks. A necessary step in understanding the dynamics of
these large scale activity patterns is to understand how local circuits with oscillatory
dynamics respond to temporally patterned inputs. We have measured two aspects of
the response dynamics of hippocampal CA3 networks during gamma oscillating states
in vitro. Firstly, we have characterised the phase response of carbachol induced
network oscillations to electrical stimulation of mossy fibres and recurrent collaterals.
This revealed biphasic phase response curves (PRCs) in which the stimulus could
advance or delay the network oscillation depending on its phase. The detailed structure
of the rephasing behaviour was reproduced with remarkable accuracy by perturbation
of the Wilson-Cowan equations. Differences between the two stimulus types could be
reproduced by varying the relative strength of input to the excitatory and inhibitory
populations of the model. Secondly, we have measured the response of CA3 gamma
oscillating networks to periodic inputs, using optogenetic stimulation to both induce
and perturb the oscillation. Intrinsic oscillations entrained to periodic inputs over a
wide range of frequencies, with the entrainment phase varying systematically with the
driving frequency.
A COMPUTATIONAL AND BEHAVIORAL STUDY OF THE PRECISION OF VISUO-SPATIAL
WORKING-MEMORY FOR SEVERAL ITEMS
Almeida R (1), Compte A (2)
(1) Karolinska Institutet, Sweden; (2) IDIBAPS, Spain
A neuronal correlate of working-memory (WM) is persistent or delay activity, that is
stimulus-selective, elevated neuronal firing observed long after stimulus offset. One
proposed computational model accounts both for electrophysiologically measured delay
activity in monkeys (Compte et al. Cereb Cortex 2000) and for behavior and
neuroimaging measurements from humans (Edin et al. PNAS 2009) acquired during a
visuo-spatial WM (vsWM) task that requires memorizing non-foveal positions located
on a circle. This computational model consists of a network of integrate-and-fire
excitatory and inhibitory neurons organized according to a ring topography in terms of
internal connectivity and external inputs received. The topography enables the model
to sustain a line attractor mechanism for vsWM. This assumption of a continuum vsWM
is essential for the model but has never been unequivocally demonstrated
experimentally. We addressed this issue by formulating two specific predictions from
the computational model that were then confirmed in behavioral experiments. The first
prediction is that the efficiency with which different simultaneously presented items are
memorized depends on their relative locations. The second prediction is that the
observed trade-off between WM precision and capacity (Bays and Husain Science
2008) depends on the relative locations of the items.
SPATIAL FREQUENCY TUNING REVEALS VISUOMOTOR INTERACTIONS BETWEEN THE
DORSAL AND VENTRAL VISUAL SYSTEMS
Almeida J (1,2), Kumar N (3) and Mahon B (3,4)
(1) Faculty of Psychology, University of Lisbon, Portugal; (2) School of Psychology,
University of Minho, Portugal; (3) Department of Brain and Cognitive Sciences,
University of Rochester, USA; (4) Department of Neurosurgery, University of
Rochester, USA
The magnocellular dominated dorsal visual system is biased toward processing low
spatial frequency (LSF) information from the visual input. We exploited this property to
test for visuomotor interactions between the dorsal and ventral visual systems.
Participants viewed images of tools and animals containing only low or only high
spatial frequencies (HSF) during functional Magnetic Resonance Imaging (fMRI). We
find an internal parcellation within left parietal 'tool preferring' voxels: tool preferences
in inferior aspects of left parietal cortex are driven by HSF information while in more
superior regions by LSF information. Furthermore, we show that inferior aspects of left
parietal cortex express differential functional connectivity to ventral stream regions that
show matching category-selective responses. Our findings demonstrate that the
automatic activation of putative dorsal stream regions involved in object manipulation
is contingent on analysis of the visual input by the ventral visual pathway.
NEUROELECTRONICS MAGNETORESISTIVE PLATFORM FOR ACTION POTENCIAL
DETECTION
Amaral J (1,2), Cardoso S (1,2), Sebastião AM (3), Freitas PP (1,2)
(1) INESC–MN/Institute for Nanosciences and Nanotechnologies, Lisbon, Portugal; (2)
Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisbon, Portugal; (3)
Laboratory of Neurosciences, Faculty of Medicine, University of Lisbon, Portugal
In the brain, hippocampus plays one of the most important role in memory; therefore
intense research has been carried out aiming a better understanding of its
mechanisms.
This work presents an alternative hybrid system based on magnetoresistive (MR)
sensors capable of measuring the magnetic response of neurons from a hippocampus
brain slice. The integration of an extracellular electrophysiology system with a
microfabricated device comprising MR sensors was used to measure the response of a
rat or mice brain slice (400 um thick) after the activation of action/synaptic potential
sources. MR sensors can be used to improve the electrophysiology techniques, offering
local measurements of extracellular currents with micron size spatial resolution.
Sequences of pulses were measured after hippocampus excitation (rectangular pulses
of 0.1 ms every 10s) by one of the spin valve sensors present in the MR sensors array
defined in the device. The pulses were recorded only in the pyramidal bodies’ cell
region and are interpreted as coming from action potential currents generated by the
activation of multiple pyramidal cells bodies.
The signal detected could arise from a capacitive coupling between the sensor leads
and the brain slice. Understanding the origin of other field sources is a challenging
step.
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HIPPOCAMPAL SYNAPTIC PLASTICITY INDUCED BY NATURAL SPIKE TRAINS AT
SINGLE DENDRITIC SPINES
Argunsah AO and Israely I
Neuronal Structure and Function Lab., Champalimaud Neuroscience Programme,
Lisbon, Portugal
Neurons process an abundance of information converging onto their inputs.
Understanding the input-output relationship is one of the cornerstones of
neuroscience. Synapses, where neurons connect to each other, are the points at which
information first arrives at cells. It is proposed that learning changes the efficacy of
synapses, and long-term ostentation (LTP) and long-term depression (LTD) are
processes by which such changes in synaptic strength can occur. Classic experimental
ways of testing memory mechanisms in CA1 cells of the hippocampus induce LTP using
high-frequency stimulation (HFS) and LTD using low-frequency stimulation (LFS).
Using glutamate uncaging, it is possible to induce LTP and LTD with high spatial
resolution at the single spine level with these protocols, although they are temporally
regular in structure unlike naturally occurring activity.
In this study, we aim to determine how natural spike trains (NSTs) affect plasticity at
single spines compared to classical LFS and HFS protocols. Based on in vivo recordings
of activity from CA3 cells, we will pattern NSTs with glutamate uncaging in order to
stimulate spines at CA1 neurons. We will also monitor the plasticity induced at these
synapses by patch-clamp electrophysiology, in order to validate the caged glutamate
protocols.
THE EFFECT OF NON-HOMOGENEOUS DELAYS ON THE SPONTANEOUS DYNAMICS OF
A RING NETWORK OF EXCITATORY AND INHIBITORY NEURONS
Baroni F (1), Nowotny T (2)
(1) The University of Melbourne, Australia; (2) University of Sussex, UK
The spontaneous dynamics of neuronal networks constrain the information
representation and processing that they can support when provided with external
inputs. In this study, we report the dynamics of a network of excitatory and inhibitory
neurons, with different intrinsic properties, spatially arranged on a ring network with
distance-dependent delays. We used the Integrate and Fire model (IF) or the
Generalised Integrate and Fire (GIF) with subthreshold oscillations as a dynamical
description for the individual units. As parameters are varied these networks can
exhibit asynchronous activity, or population spikes of different spatial extent, temporal
regularity and reproducibility. We extracted the spatial positions from a uniform
distribution, and observed that both the average firing rate across neurons and the
phase relationships were strongly affected by the precise realisation of the layout.
When compared with networks with regularly arranged neurons, small heterogeneities
in neuronal density constrain the activity of the network and increase the average
coherence between neurons. If the spatial positions of excitatory and inhibitory
neurons are extracted from different distributions, this stronger heterogeneity further
constrains the activity of the network. In this case, population spikes are highly
reproducible.
THE MOLECULAR AND NEURONAL CONTROL OF FOOD CHOICE IN DROSOPHILA
Célia Baltazar, Ana Carolina Doran, Ana Paula Elias and Carlos Ribeiro
Behaviour and Metabolism Laboratory, Champalimaud Neuroscience Programme,
Champalimaud Centre for the Unknown, Lisbon, Portugal
Animals often decide between alternative actions according to their current needs, and
hence the value they assign to each of the competing options. This process is of
special relevance during nutrient balancing, in which animals choose between different
food sources according to their current nutritional state. How such value-based
decision making is implemented at the molecular and neuronal level in the brain is not
well understood.
We have described Drosophila food choice as a genetically tractable model to study
value-based decision making in the context of nutrient balancing. When faced with the
choice between yeast and an alternative food source, flies deprived of protein prefer
the yeast. Mating status is a critical modulator of this decision-making process in
females, relying on the action of the sex peptide receptor (SPR) in ppk+ sensory
neurons. Neuronal TOR/S6K function is another critical input to this decision, possibly
signaling the fly’s current nutritional status.
More recently we have been focusing on identifying additional neuronal subsets
required for this nutritional homeostatic process. We have identified 8 Gal4 lines
labeling neurons required specifically during the decision making process. The
identification of the involved neuronal substrate is an important step towards our goal
of generating a molecular and cellular understanding of how neuronal systems sense
metabolic needs and modify neuronal processes to produce the correct behavioral
decisions needed for the survival and reproduction of an organism.
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NEUREGULIN-1 SIGNALING IN NEURAL CIRCUIT ESTABLISHMENT: IMPLICATIONS
FOR SCHIZOPHRENIA
Barros CS (1,2), Cahill M (3), Calabrese B (2), Chamero P (2), Roberts A (2), Korzuz E
(2), Stowers L (2), Mayford M (2), Halpain S (2), Penzes P (3), Muller U (2)
(1) School of Biological Sciences, Bangor University, UK; (2) The Scripps Research
Institute, USA; (3) Northwestern University, USA
Neuregulin-1 (NRG1) and its ErbB2/B4 receptors are encoded by candidate
susceptibility genes for schizophrenia. Using CRE/LOX technology, we have inactivated
ErbB2/B4-mediated NRG1 signaling specifically in the central nervous system. While
cortical cell layers develop normally in the mutant mice, synaptic maturation and
interactions between postsynaptic scaffold proteins and glutamate receptors are
impaired. Loss of ErbB2/B4 further inhibits interneuron dendritic growth, while ectopic
NRG1 increases dendritic length. This effect can be abolished by down regulation of
Kalirin-7, a major dendritic Rac1-GEF and binding partner of ErbB4.
ErbB2/B4-deficient mice show increased aggression and reduced prepulse inhibition,
behavioral abnormalities associated with schizophrenia-like symptoms. Treatment with
the antipsychotic drug Clozapine reverses both behavioral and postsynaptic defects.
We conclude that ErbB2/B4-mediated NRG1 signaling modulates synapse maturation
and interneuron dendritic growth, defects that likely contribute to the behavioral
abnormalities in ErbB2/B4-deficient mice and may underlie aspects of schizophrenia
pathology.
BEHAVIOURAL LATERALISATION AND AVOIDANCE BEHAVIOURS CORRELATE WITH
CNS ASYMMETRIES
Anukampa Barth, Elena Dreosti and Stephen W Wilson
Department of Cell and Developmental Biology, University College London, UK
The exquisite efficiency of many cognitive and behavioural processes is thought to be
achieved by asymmetric processing of information in the CNS. Despite the fact that
alteration of such asymmetries correlates with several neuropathologies, little is known
about their development or detailed neurocircuitry.
The asymmetry of epithalamic neurocircuitry of zebrafish, comprising the bilateral
habenular nuclei and the asymmetric pineal complex, is one of the best models to
study the formation of brain asymmetries and lateralised behaviours.
We have previously shown that habenular asymmetries correlate with eye preference
when viewing conspecifics, and that the orientation of this bias is reversed in mutant
fry that show reversal of these asymmetries. Surprisingly, alteration of epithalamic
asymmetry to a more ‘symmetric’ pattern does not abolish laterality of eye preference.
In addition, visual stimuli presented to one eye can elicit stronger aversive responses
than to the other eye, and fry with ‘reversed’ or more ‘symmetric’ brains show less
aversion to familiar visual cues than do normally lateralised fry.
Combining behavioural assays with functional imaging techniques will allow us to
assess if molecular and neuroanatomical asymmetries predict functional asymmetries,
and to establish if and how lateralized behaviours are influenced by the epithalamic
circuitry.
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MODULATION OF GLUCOCORTICOID RECEPTOR (GR) TRANSCRIPTIONAL ACTIVITY
BY ADENOSINE A2A RECEPTORS: CONSEQUENCES FOR STRESS RESPONSE.
Vânia L. Batalha (1), Malika Hamdane (2,3), Ana M. Sebastião (1), Luc Buée (2,3,4),
David Blum (2,3,4), Luísa V. Lopes (1)
(1) Neurosciences Unit, Instituto de Medicina Molecular, University of Lisbon and
Institute of Pharmacology and Neurosciences, Faculty of Medicine of Lisbon, Portugal;
(2) Univ. Lille-Nord de France, UDSL, Faculté de Médecine, IMPRT, Lille, France; (3)
Inserm, UMR837, “Alzheimer & Tauopathies”, Lille, France ; (4) CHRU-Lille, Jean-Pierre
Aubert Research Centre, Lille, France
Adenosine A2A receptors (A2AR) are important modulators of brain excitability and
plasticity. We previously observed that A2AR blockade reestablishes HPA-axis function
and plasmatic corticosterone levels in chronically stressed animals. Here, we
investigated whether A2AR modulate directly GR transcriptional activity.
N1E115 cells were transiently transfected with PGL(GRE)3tk vector coding luciferase
under the control of Glucocorticoid-Response-Elements to monitor GR-dependent
transcription using a luciferase assay. Dependency upon A2AR was evaluated using an
A2AR selective agonist (CGS21680,10-100nM) or antagonist (SCH58261,10-100nM),
with or without dexamethasone. Interestingly, the antagonist decreased basal GRdependent transcriptional activity by 33±6%(n=6-8,p<0.001), while the agonist
increased it by 37±15%(n=3-5,p<0.01).
These effects were reproduced when GR were activated by dexamethasone(n=3-7). In
accordance, using primary neuronal cultures, we found that A2AR modulate GR nuclear
translocation. Indeed, 60 min following dexamethasone exposure, GR
nuclear/cytoplasmic ratio was 1.30±0.20, whereas in the presence of SCH58261 it was
significantly reduced to 0.61±0.03(n=3-4,p<0.01).
The present results show that A2AR modulate glucocorticoid effects by regulating
transcriptional activity and nuclear translocation of GR. This may be the underlying
mechanism for the therapeutic effects elicited by A2AR blockade.
(Funded by FCT, Inserm and EU Égide Pessoa program).
CONSOLIDATING UNIQUE MEMORIES: BDNF IN THE DENTATE GYRUS IS REQUIRED
FOR SPATIAL PATTERN SEPARATION
Pedro Bekinschtein, Lisa M. Saksida and Timothy J. Bussey
Department of Experimental Psychology and MRC and Wellcome Trust Behavioural and
Clinical Neuroscience Institute, University of Cambridge, Cambridge, United Kingdom
To allow similar episodes to be distinguished in memory, the brain must form distinct
representations of these events. The computational process for making representations
for similar input patterns more orthogonal to and distinct from each other has been
referred to as ‘pattern separation’. Recent studies have suggested that the brain region
crucial for the process of spatial pattern separation is the dentate gyrus (DG) of the
hippocampus. It is largely unknown however, what mechanisms and molecules
underlie pattern separation. Here we show that both activity and expression of BDNF in
the DG are required for memory encoding and/or consolidation of similar, but not
dissimilar spatial representations in the DG. We also provide the first experimental
evidence that a BDNF-dependent pattern separation process occurs during the
encoding/storage/consolidation, but not the retrieval stage of memory processing.
Finally, we found a spontaneous increase in BDNF in the DG is associated with
exposure to landmarks delineating similar, but not dissimilar spatial locations,
suggesting that BDNF is expressed on an “as-needed” basis for pattern separation.
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A PRIMAL NEURAL CIRCUIT FOR GAZE STABILIZATION
Bianco IH* (1), Ma LH* (2), Schoppik D* (1), Robson DN (1), Orger MB (3), Beck
JC (2), Li JM (1), Schier AF (1), Engert F (1), Baker R (2)
(1) Department of Molecular and Cellular Biology and Centre for Brain Science, Harvard
University, Cambridge, MA, USA; (2) Department of Physiology and Neuroscience, New
York University School of Medicine, NY, USA; (3) Champalimaud Neuroscience
Programme, Lisbon, Portugal
Whilst adult vertebrates sense changes in head position using two classes of
accelerometer, larval zebrafish lack functional semicircular canals, relying exclusively
on the utricle to transduce vestibular information. Surprisingly, we found that larval
zebrafish respond to both static gravitational forces and dynamic accelerations with a
highly effective and remarkably broadband vestibulo-ocular reflex (VOR), enabling
identification of a fundamental neural circuit responsible for gaze stabilization. Using
single-cell electroporation and laser ablation, we identified second-order neurons in the
tangential nucleus that are necessary for the VOR. Further, tangential neurons
innervate premotor reticulospinal neurons, allowing coordination of ocular
compensation and head/body posture. In sum, sensorimotor neurons in the tangential
nucleus operate as a broadband inertial accelerometer, processing utricular
acceleration signals to control the activity of extraocular and postural neurons, thus
completing a primal three-neuron circuit responsible for gaze stabilization.
SINGLE CELL TRANSCRIPTOMICS REVEALS MICROTUBULES AS A SENSOR
TRIGGERING CNS REPAIR
Bossing T (1), Barros CS (1), Fischer B (2), Russell SR (2), Shepherd D (1)
(1) Bangor University, UK (2) Cambridge University, UK
The mechanisms of damage repair in the central nervous system (CNS) are
fundamental biological processes with vital medical implications. We show that
traumatic injury to the ventral midline of the embryonic Drosophila CNS activates
mitosis in adjacent midline cells, and single cells lost by damage can be fully replaced
by their siblings. Analysis of transcriptional changes in single cells during the early
phase of repair uncovered the transcriptonal factor jun (jra) as a highly upregulated
transcript. In agreement, loss of jra renders midline cells unable to replace damaged
siblings. dMiro, a GTPase stabilising microtubules, was the highest downregulated
transcript identified. Ectopic expression of dMiro can prevent divisions after damage,
whereas depletion of dMiro increases midline divisions. Also, depolymerisation of
microtubules or tubulin overexpression, drives midline cells towards mitosis and
activates the expression of jra. Our data indicate that the integrity of the microtubules
cytoskeleton may act as a sensor for cell damage triggering extra divisions to replace
lost cells. The ependymal nature of the ventral midline and the conservation of the
identified transcripts suggest similar mechanisms may exist in the vertebrate CNS.
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HOW TO DEAL WITH THE HETEROGENEITY OF NEURAL RESPONSES: A DEMIXING
METHOD
Brendel W (1), Uchida N (3), Romo R (2) and Machens CK (1)
(1) Champalimaud Neuroscience Programme; (2) Universidad Nacional Autónoma de
México; (3); Harvard, FAS Molecular & Cell Biology
Higher brain areas receive inputs from many parts of the brain. The activity of neurons
in these areas often reflects this mix of influences. As a result, neural responses are
extremely complex and heterogeneous, even in animals performing relatively facile
tasks. The traditional approach to analyzing data from neural populations essentially
ignores the problem and simply focuses on the responses of single neurons, selecting
some for presentation, and submerging the rest in a swamp of statistical measures.
More recent approaches have sought to analyze recordings by resorting to principal
component analysis (PCA) and other dimensionality reduction techniques. These
techniques provide a succinct description of the population response, however, the
construction of this description is independent of the relevant task variables. We
propose a data analysis method that seeks to maintain the major benefits of PCA while
also extracting the relevant task variables from the data. We suggest that task
variables will often find orthogonal representations in higher-order areas. Therefore,
we propose a dimensionality reduction method that seeks a coordinate transformation
such that firing rate variance caused by different task variables falls in orthogonal
subspaces and is maximized within these subspaces. We study use of the method for
neural population recordings obtained in monkeys and rodents.
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TOWARDS A SEMI-ANALYTICAL PROBABILITY DENSITY FOR THE TRANSFER
FUNCTION OF NEURONS
Brigham M and Destexhe A
UNIC CNRS, France
Mean-field approaches have been successfully used to model macroscopic neuronal
activity, where the computational unit is a population of neurons rather than a single
neuron. A key ingredient is the so-called transfer function, which maps the population
response as a function of input activity statistics.
In such a context, shot-noise processes are a very useful framework for realistic
models of pre-synaptic activity. However, a general analytical description of shot-noise
synaptic inputs is not available. In practice, only the first statistical moments (mean
and variance) are used to model pre-synaptic inputs as these are readily available
through Campbell Theorem.
In this study, an analytical characterization of shot-noise synaptic inputs typically used
in computational neuroscience has been obtained in frequency space. This enables
very precise numerical estimation of the shot noise propagator (in particular for low
activity input regimes). The probability density of the transfer function is then obtained
by computing the transformation of shot noise propagator under the membrane
equation of the neuron.
This work opens the perspective of obtaining higher order mean-field models for
neurons with realistic synaptic inputs.
MODELING THE DYNAMICAL MECHANISM OF BAND SPECIFIC MEG FUNCTIONAL
CONNECTIVITY DURING REST.
Cabral J (1,2), Luckhoo H (3), Woolrich M (3), Joensson M (2,4), Mohseni H (2),
Kringelbach M (2,4), Deco G (1,5)
(1) Center for Brain and Cognition - UPF, Spain; (2) Dept. of Psychiatry, Univ. of
Oxford, UK; (3) Oxford Ctr. for Human Brain Activity, Univ. of Oxford, UK; (4)
CFIN/MindLab - Aarhus Univ., Denmark; (5) ICREA, Spain.
The mechanisms underlying the organized patterns of cortical oscillations during rest
remain under debate. Progress has been made through the identification of restingstate networks in slow BOLD signal fluctuations. More recently, a resting-state MEG
study has identified the same underlying networks using fluctuations in the amplitude
of alpha and beta frequency band oscillations (Brookes et al., submitted).
Using computational models can help uncovering the hidden dynamical mechanisms.
In Cabral et al. (2011), resting-state BOLD signal correlations are predicted using
simulations with weakly coupled gamma-band oscillators connected in a network built
with realistic brain connectivity and conduction delays. Here, we used the same
computational model to predict experimental resting-state MEG data. For realistic
delays and using intrinsic oscillations in the gamma-band, meta-stable oscillatory states
occur in the alpha and beta frequency bands. In this dynamical regime, the fluctuation
in the synchrony degree of a group of nodes modulates their band-specific power in
time. In Cabral et al. (2011), BOLD fluctuations were explained by slow fluctuations in
the synchrony degree. Here, we show that these fluctuations also modulate the power
in the alpha and beta frequency bands, which is suggestive of general computational
principles underlying spontaneous brain oscillations.
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PHEROMONE PROCESSING IN A SEXUALLY DIMORPHIC OLFACTORY CIRCUIT
Cachero S, Ostrovsky AD, Kohl J, Frechter S, Jefferis GSXE
MRC Laboratory of Molecular Biology, Cambridge, UK
We are investigating the neural circuit basis of olfactory perception in Drosophila.
Olfactory information enters the fly brain in 50 glomeruli of the antennal lobe. Second
order neurons then project to two structures, the mushroom body, which is required
for olfactory learning but apparently dispensable for innate olfactory behaviour, and
the lateral horn. We have previously demonstrated that olfactory input to the lateral
horn is spatially stereotyped across individuals and that pheromone and general odours
are mapped to different zones. We hypothesise that this poorly characterised brain
centre is where odour information starts to be transformed into behaviourally relevant
representations.
One initial focus has been on the processing of the pheromone signal cVA, a male
pheromone that is repulsive for other males but a female aphrodisiac. We have
recently shown striking anatomical dimorphisms in the dendrites of third order lateral
horn neurons that appear to receive cVA information from incoming projection neuron
axons. Two small groups of neurons show male specific overlap while a third shows
overlap in females. We are currently investigating the physiology of these neurons in
both sexes; we hypothesise they will be the first neurons to show differential
pheromone responses between the sexes.
COMPUTATIONAL MODELING OF SEROTONERGIC MODULATION IN A PREFRONTAL
CIRCUIT FOR WORKING MEMORY
Cano-Colino M, Almeida R, Compte A
IDIBAPS, Barcelona, Spain
Serotonin (5-HT) is known to have profound effects in cognitive function and
perception. Understanding these effects is of especial relevance since drugs acting on
5-HT receptors are used to treat the symptoms of schizophrenia (atypical
antipsychotic). Receptors of types 1A and 2A are known to be massively expressed in
prefrontal cortex (PFC) neurons, an area that is thought to mediate cognitive function.
Hence, the effects of 5-HT release in PFC circuits and cognitive functions are expected
to be important, although difficult to predict, since both receptors have opposite effects
on the excitability of PFC neurons. Here, we investigate the effect of 5-HT receptor
activation on a neuronal network model of working memory (WM). Selective PFC
activity during WM has been shown to be modulated through local 5-HT receptor
activation. Its also known that behaviorally, systemic administrations of 5-HT agonists
produceWM deficits in humans. We develop a computational model to study the 5-HT
modulation of WM function. We depart from a neuronal network model which has been
shown to reproduce the activity of neurons in PFC of monkeys performing a visuospatial WM task. It consists of a network of integrate-and-fire excitatory and inhibitory
neurons. We modified the equations describing the single neurons to include the
effects of activation of 5-HT receptors. We test the model by comparing it to the
physiological effects of tonic and phasic 5-HT. We then characterize the impact of 5-HT
manipulations in WM function in terms of memory stability and resistance to
spontaneous formation of patterns of activity, from which we infer specific predictions
regarding 5-HT modulation of WM performance. Finally, we modified the parameters of
the network to model the WM function of psychotic networks built according to the
GABAergic and Glutamatergic hypotheses of schizophrenia and then we study how the
atypical antipsychotics can improve disordered thought symptoms of these networks.
30
PHASE PRECESSION THROUGH ACCELERATION OF LOCAL THETA RHYTHM: A
BIOPHYSICAL MODEL FOR THE INTERACTION BETWEEN COMPLEX SPIKE CELLS AND
THETA CELLS
Castro L, Aguiar P
Centro de Matemática da Universidade do Porto, Portugal
Coding information in the hippocampus through phase-precession means that the
phase in the theta cycle in which a place cell fires provides information regarding the
position of the rat in the place field. Here we present a biophysical model for phase
precession in hippocampal CA1 cells which focuses in the interaction between complex
spike cells and theta cells in the CA1 field. The model's functional block is composed of
a complex spike cell receiving input from a theta cell which is in turn modulated by the
population theta rhythm. The dynamics of the two neuron types are described by
Integrate-and-Fire models with conductance based synapses. Phase precession in our
model is explained as a consequence of local theta acceleration: although all theta cells
form a weakly coupled network modulated by the theta rhythm, increased excitation to
the pair complex spike cell/theta cell leads to a local acceleration of the theta cells'
average firing frequency. The complex spike cell, modulated locally by the theta cell(s)
with a rhythm which is slightly faster than the population theta, undergoes phase
precession. Only complex spike cells, and associated theta cells, receiving more
excitation (inside their respective place field) will exhibit phase precession.
SPARSE CODING IN THE AUDITORY SYSTEM OF GRASSHOPPERS
Jan Clemens (1,2), Olaf Kutzki (1), Bernhard Ronacher (1), Susanne Schreiber (1,2),
Sandra Wohlgemuth(1)
(1) Bernstein Center for Computational Neuroscience Berlin, Germany; (2) HumboldtUniversität zu Berlin, Germany
Optimal coding principles are implemented in many large sensory systems. They
include the systematic transformation of external stimuli into a sparse and decorrelated
neuronal representation, enabling a flexible readout of stimulus properties. Are these
principles also applicable to size-constrained systems, which have to rely on a limited
number of neurons and may only have to fulfill specific and restricted tasks?
We studied this question in the early auditory pathway of grasshoppers. Grasshoppers
use genetically-fixed songs to recognize mates. The first steps of neural processing of
song take place in a small three-layer feed-forward network comprising only a few
dozen neurons. We find that grasshoppers create a decorrelated and sparse
representation of song in accordance with optimal coding theory. At the output stage,
information about song identity is maximal for a population decoder that preserves the
neuronal identity of spikes. This indicates that a labeled-line code for temporal features
of the song is established.
In contrast to larger sensory systems, the neuronal representation of song is not
systematic or map-like. Already at its periphery, part of the grasshopper auditory
system seems to focus on behaviorally-relevant features and is in this property more
reminiscent of higher sensory areas in vertebrates.
31
ENCODING OF OSCILLATORY PHASE VS. MEMBRANE DEPOLARIZATION BY INFERIOR
OLIVARY BURSTS IN-VIVO
Cohen E and Lampl I
Weizmann Institute for Science
Recent recordings of inferior olive (IO) neurons in slices suggest that the number of
high frequency spikes in a single axonal burst (less than 5ms long) may encode the
phase of subthreshold membrane oscillation during spike initiation. Accordingly, these
bursts are then transmitted via the climbing fibers and result in variant number of
EPSPs which generate complex spikes (CS). The number of EPSPs may thereafter
affect the real-time output of Purkinje cells (PCs) as well as the plastic changes in their
parallel fiber synapses. We used intracellular recordings in awake and anesthetized rats
to address two major aspects regarding this question:
A.
Does such encoding exist in in-vivo preparations?
B.
Is the encoding is of oscillatory phase per se or of membrane potential
depolarization?
PCs in awake rats showed variant number of climbing fiber EPSPs, with similar
distributions to distributions of IO bursts. IO recording in anesthetized rats supported
weak phase correlations in half of the analyzed neurons; however, our data suggest
that the number of axonal spikes better encode the average pre-spike depolarization.
Thus, our findings give rise to a more complex phase encoding scheme, which may
depend on both oscillatory state and synaptic responses.
REWARD LEARNING PREVENTS SPONTANEOUS RECOVERY OF FEAR
Susana S. Correia, Ann M. Graybiel and Ki Ann Goosens
Department of Brain and Cognitive Sciences and McGovern Institute for Brain
Research, MIT, Cambridge, MA, USA
Previous studies have shown that the successful avoidance of an aversive outcome can
activate brain areas generally associated with the experience of a reward (Kim et al.,
2006). Likewise, during extinction of fear, the expected aversive stimuli is avoided,
suggesting that fear extinction memories could be encoded in brain areas involved in
reward learning. We hypothesized that training rats to associate a fear-provoking
stimulus with reward delivery would result in a more durable fear extinction memory
than fear extinction training alone. All rats received auditory fear conditioning. Some
rats received extensive auditory extinction training, whereas other rats received
moderate extinction training followed by Pavlovian reward training with the same tone.
Spontaneous recovery of fear was measured in both groups. Our data revealed that
rats trained to associate the previously fearful tone with a reward delivery exhibited no
spontaneous recovery of fear, suggesting that the extinction memory is more
persistent when rats learned to associate the tone with a positive value. Our ongoing
work uses in vivo physiology and molecular markers of activity to identify brain circuits
that participate in both fear extinction and reward learning.
We believe this approach could be used to improve the treatment of disorders thought
to result from a failure to extinguish fear memories, including anxiety disorders and
Post-Traumatic Stress Disorder (PTSD).
32
TESTING THE ORIGIN OF UNCERTAINTY IN THE TRANSFORMATION OF OLFACTIONTO-ACTION
Gil Costa (1,2), Adam Kepecs (3) and Zachary F. Mainen (1)
(1) Champalimaud Neuroscience Programme, Champalimaud Center for the Unknown,
Lisboa, Portugal; (2) PhD Programme in Experimental Biology and Biomedicine
(PDBEB), Center for Neuroscience and Cell Biology, Coimbra, Portugal; (3) Cold Spring
Harbor Laboratory, New York, USA
Difficult decisions can occur because stimuli are hard to perceive or because the rules
of what should be done given a certain stimulus are uncertain. We would like to
understand how such uncertainty is represented by the brain and may be assessed and
used for adaptive behavior. To do so, we have been studying a perceptual decision
task in which rats perform a binary categorization of an odor mixture and report their
decision confidence by reward waiting time (Kepecs at al., 2008). Recordings from the
anterior piriform cortex (aPCx), together with previous behavioral results, suggest that
rats have a high fidelity representation of the odor cue, but that variability is
introduced downstream of this sensory representation. We hypothesize that the
olfactory tubercle (OT, an olfactory striatum) is the site where odor representations are
linked to action values and therefore the site at which uncertainty in the olfactory
categorization task originates. To test this, we are conducting electrophysiological
recordings from multiple single units in aPCx and OT. Our behavioral paradigm includes
not only odor mixtures of different difficulty and report of confidence, but also variation
of reward magnitude that will allow us to dissociate confidence and value
representations.
THE DIVERSITY OF THALAMORECIPIENT SPINE MORPHOLOGY IN CAT VISUAL
CORTEX AND ITS IMPLICATION FOR SYNAPTIC PLASTICITY
Nuno Maçarico Costa and Kevan Martin
Institute of Neuroinformatics, UZH/ETHZ, Zurich, Switzerland
A feature of spine synapses is the existence of a neck connecting the synapse on the
spine head to the dendritic shaft. As with a cable, spine resistance increases with
increasing neck length and is inversely proportional to the cross-sectional area of the
neck. A synaptic current entering a spine with a high resistance will lead to greater
local depolarization in the spine head than would a similar input applied to a spine with
a lower resistance. This could make spines more sensitive to plastic changes, eg.
voltage sensitive NMDA channels, which in turn would increase AMPA synapse size due
to insertion of AMPA receptors. Here we test if longer and thinner spines have bigger
synapses.
Thalamic axons and corticothalamic neuron were labeled by injections of the tracer
BDA in the dorsal lateral geniculate nucleus (dLGN) of anaesthetized cats. After
recovery of one week, the cats were again anaesthetized and single neurons were
recorded in area 17 and filled intracellularly with horseradish peroxidase. Twenty-five
labeled spines that formed synapses with dLGN boutons were collected from 3 spiny
stellate and 4 corticothalamic cells and reconstructed in 3-D from serial electron
micrographs. Spine length, spine diameter and synapse area were measured from the
3-D reconstructions and the electric resistance of the spine was estimated (R = (neck
length / neck cross-sectional area) " neck resistivity).
No correlation was found between size of a synapse and the estimated spine neck
resistance (r2 = 0.004). This suggests that forms of plasticity that lead to larger
synapses do not occur in spines with higher input resistance. Project supported by
NCCR grant Neuroplasticity and Repair and European Union SECO Grant number
216593.
33
WHY SNIFF STRONG WHEN SNIFF FAST: DECIPHERING THE EFFECTS OF FREQUENCY
AND FLOW RATE VARIATION ON OLFACTORY BULB ACTIVITY
Courtiol E, Esclassan F, Fourcaud-Trocmé N, Garcia S, Litaudon P, Buonviso N
Centre de Recherche en Neurosciences de Lyon, CRNL, CNRS UMR 5292, INSERM U
1028, UCBL, team olfaction from coding to memory, France
Olfactory sampling behaviour (namely sniffing) seems to be part of the olfactory
percept. First, olfactory bulb (OB) activity is known to be highly related with
respiration. Second, sniffing is highly variable (Youngentob, 1987) thus adjusting odor
molecules sampling to the animal's needs. Nevertheless, impact of sniffing variations
on odor coding in the OB was poorly studied. In a first study (Courtiol et al., 2011), we
showed that nasal flow rate had a strong effect on Mitral/tufted (M/T) cell activity,
Local field potential (LFP) oscillations, and on the synchronization between spikes and
LFP oscillations. However, the question of how frequency and flow rate individually or
synergistically impact bulbar activity has never been approached. For this purpose, we
first used an anesthetized preparation of double-canulation tracheotomized rats
allowing a fine control of nasal airflow dynamics. Both LFP and M/T cell responses to
odors were recorded. Our results highlight a tradeoff effect between frequency and
flow rate on OB odor response. Second, we confirmed that such a co-variation of
frequency and flow rate also occurs in awake animals.
This work was supported by a grant from "Agence Nationale de la Recherche"
(ANR-07-NEURO-030).
FREQUENCY DEPENDENT RESPONSE AND RELIABILITY OF SPIKE TIMING IN
CEREBELLAR PURKINJE NEURONS IN VITRO
Couto J (1), De Schutter E (1,2), Giugliano M (1,3,4)
(1) Theoretical Neurobiology, UA, Antwerp, Belgium; (2) Computational Neuroscience
Unit, OIST, Okinawa, Japan; (3) Brain Mind Institute, EPFL, Lausanne, Switzerland; (4)
University of Sheffield, Sheffield, UK
The cerebellum is involved in the control of fine movements coordination. To
understand how the cerebellum processes information at the cellular level, a detailed
understanding of how individual neurons process their incoming synaptic inputs is
imperative. In particular, Purkinje cells represent the single output of the cerebellar
cortex and possess unique morphology and functional connectivity. These cells are
known to fire spontaneously and manifest electrical bi-stability both in vivo and in vitro.
It has been recently proposed that Purkinje cells behave as phase-independent
integrators at low output spiking rates, while they switch into a phase-dependent
electrophysiological regime at high spiking rates. Such properties make the
investigation of the dynamic properties of cerebellar Purkinje neurons a priority.
Using patch-clamp intracellular recordings from the somata of Purkinje cells in acute
cerebellar tissue slices, we have investigated the dynamic response properties of
cellular input-output response properties, characterizing the reliability of spike timing
using noisy current injection, the inter-spike interval variability at both low and high
firing rate, and the impact of uncorrelated background synaptic activity. Combining
together these features of Purkinje cells response properties might significantly boost
our understanding of their overall functional contribution in cerebellar microcircuitry as
well as as of their role at its output stage.
34
CALCIUM SIGNALLING MODULATION BY ADENOSINE RECEPTORS IN ASTROCYTES
Cruz-Silva A (1,2), Jacob JP (1,2), Vaz SH (1,2), Ribeiro JA (1,2), Sebastião AM (1,2)
(1) Institute of Pharmacology and Neuroscience, Faculty of Medicine; (2) Unit of
Neuroscience, Institute of Molecular Medicine, University of Lisbon, Portugal
Purines, namely adenosine and ATP, modulate gliotransmission, regulating synaptic
transmission and ultimately neuron-astrocyte communication. ATP triggers a calcium
response in cortical astrocytes. ATP is extracellularly converted in adenosine and recent
results from the host group demonstrate that adenosine receptors, A1 and A2A,
modulate GABA uptake in cortical astrocytes, but most importantly that this modulation
is dependent on A1R-A2AR cooperation. Therefore, our purpose was to explore the
cross-talk between adenosine receptors in astrocytes and to evaluate their role in
calcium signaling modulation.
Calcium responses of cortical primary astrocytes were studied by calcium imaging
technique using Fura-2AM, at 22ºC. Cells were locally and briefly (0.2 seconds)
stimulated with ATP 10microM (non-saturating concentration) and the amplitude of the
responses was measured.
A stable adenosine analogue, 2-Chloroadenosine (1microM), markedly enhanced
calcium response induced by ATP (fold increase – 3.19±0.30, n=72 cells). A specific
A2AR agonist, CGS 21680 (30nM), mimicked this effect (2.92±0.32, n=80 cells). The
potentiation mediated by both agonists was not only reverted by a specific A2AR
antagonist, SCH 58261 (50nM), but also by a specific A1R antagonist, DPCPX (50nM).
It is concluded that adenosine, through A2AR activation, potentiates calcium signalling
in astrocytes. Furthermore, A1R-A2AR cooperation seems to be required for this
modulation.
A MINIMAL MODEL OF CEREBRAL ENERGY METABOLISM AND THE REGULATION OF
BLOOD FLOW
Dehmelt FA (1, 2), Machens CK (1)
(1) Champalimaud Neuroscience Programme, Lisbon, Portugal; (2) Ecole Normale
Superieure, Paris, France
Local brain activity produces a wide range of experimentally accessible signals, the
most prominent of which are electrical activity (as measured by electrodes, EEG, etc.)
and haemodynamic activity (as measured by fMRI). While much work has focused on
how these two are linked, little quantitative or computational work has addressed the
question of why there is haemodynamic activity in the first place. Given that blood flow
is tightly linked to the regulation of cellular metabolism, the haemodynamic response is
likely to balance two needs of the organism. One is to supply cells with necessary
resources in a timely manner, avoiding starvation. The other is to avoid constant
oversupply, as this would be an inefficient drain on the overall resources available. To
quantify how these needs are balanced in practice, we construct a minimal metabolic
model, linking the supply of metabolites from blood to the production of ATP.
Preliminary results indicate that our model indeed reproduces the timescale and steady
state of haemodynamic activity. To evaluate the efficiency of the underlying control
policy, we quantify its energetic cost over time. Finally, we compare the time course of
blood flow control observed experimentally to the optimal control policy under given
constraints.
35
MAPPING THE GENETIC NETWORKS THAT CONTROL DENDRITIC ARBOR SHAPE
Delandre C (1), Akimoto S (1), Gao F (2), Geschwind DH (2), Moore AW (1)
(1) RIKEN Brain Science Institute, Japan; (2) University of California Los Angeles, USA
The dendritic arbor is the chief site of signal input into a neuron and its shape varies
significantly among different neuron classes. The computational properties of each
neuron class arise from its specific collection and distribution of receptors and ion
channels, which are in turn delineated by class-specific dendritic arbor shape. How is
the basic neuro-developmental program altered to give rise to neurons with different
dendritic arbor shapes?
The Drosophila larval peripheral nervous system contains a group of sensory neurons
called dendritic arborization (da) neurons, classified depending on dendritic branching
complexity. Several transcription factors control da neuron morphology: Abrupt
promotes a simplified shape by inhibiting both dendritic growth and branching,
whereas Cut and Knot act on different aspects of the cytoskeleton to drive branching
complexity. By manipulating the expression of these transcription factors, we obtained
dendritic arbors with varying degrees of branching complexity. We investigated how
the transcriptome differs among samples of wild-type da neurons and those
overexpressing Abrupt, Cut, or Knot. We used the Weighted Gene Coexpression
Network Analysis to identify gene interactions required for dendritic development. This
analysis reveals highly connected genes, which we predict to have central roles in
arborization. Our future studies will validate these candidates.
EMOTIONAL VALENCE ENCODING IN AMYGDALA CIRCUITS
Demmou L (1), Bacelo J (1), Stadler M (1), Herry C (2), Müller C (1) and Lüthi A (1)
(1) Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland; (2)
INSERM U862 Neurocentre Magendie, Bordeaux, France
Although the amygdala is known to be involved in learning and memory of both
positive and negative affects, the neuronal processing of opposite emotional valences
in amygdala circuits remains poorly understood. Recent work from our team has
described two distinct neuronal subpopulations in the basal amygdala, whose activity is
correlated with fear conditioning and fear extinction, respectively (Herry et al., 2008).
However, it remains unclear whether basal amygdala neurons encode conditioned and
extinguished stimuli independent of valence, or whether CS valence is also
represented. In order to address this question, we have developed a behavioral
paradigm allowing for conditioning opposite emotional valences on a purely Pavlovian
basis. In this paradigm, repeated pairings of an initially neutral stimulus (the
conditioned stimulus: CS, i.e. tone), with an emotionally salient event (the
unconditioned stimulus: US, i.e. foot-shock or intra-oral infusion of sucrose) lead to
valence-specific conditioned-responses upon subsequent CS presentations (i. e.
freezing or orofacial taste reactions, respectively). In combination with single-unit
recordings in the basal nucleus of the amygdala, this paradigm allows us to study the
neuronal substrates of appetitive and aversive learning and to determine whether or
not memories of different emotional valences share the same circuits.
36
CHRONIC STRESS FUNCTIONALLY BIASES FRONTOSTRIATAL CIRCUITS TOWARD THE
EXECUTION OF HABITS
Dias-Ferreira E (1,2,3,4), Sousa JC (2), Jin X (3), Cerqueira JJ (2), Sousa N (2),
Costa RM (1,3)
(1) Champalimaud Neuroscience Programme at Instituto Gulbenkian de Ciência,
Portugal; (2) Life and Health Sciences Research Institute (ICVS), School of Health
Sciences, University of Minho, Portugal; (3) Section on In Vivo Neural Function,
Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and
Alcoholism, National Institutes of Health, USA; (4) PhD Programme in Experimental
Biology and Biomedicine (PDBEB), Center for Neuroscience and Cell Biology, University
of Coimbra, Portugal
The ability to shift between different action strategies is necessary for adaptation to
unpredictable environments. We previously showed that chronic unpredictable stress
promotes a bias towards the execution of habits versus intentional actions. We
uncovered that lever-pressing to obtain food rewards in rats and mice submitted to
chronic stress became insensitive to changes in outcome value and action-outcome
contingency. Furthermore, we found that chronic stress caused opposing structural
changes in the corticostriatal circuits mediating these different action strategies, with
atrophy of medial prefrontal cortex (mPFC) and dorsomedial striatum (DMS), and
hypertrophy of dorsolateral striatum (DLS). We therefore recorded the simultaneous
activity of neuronal ensembles in these circuits during training, and observed that in
stressed mice, contrary to controls, training was accompanied by 1) a decline in
functional frontostriatal interactions, and 2) a shift in the pattern of lever-press related
activity with DLS being more engaged and DMS becoming progressively less engaged.
Interestingly, chronic stress did not affect baseline firing rate, suggesting that the
observed shift in neuronal activity emerged during lever-press training leading to a
shift in action mode. These data suggest that chronic stress functionally biases the
activity in frontostriatal circuits toward the execution of habits versus intentional
actions.
ENHANCED LTP IN AGEING IS DEPENDENT ON ENDOGENOUS BDNF
Diógenes MJ (1,2), Costenla AR (1,2), Lopes LV (1,2), Jerónimo-Santos A (1,2),
Sousa VC (1,2), Fontinha BM (1,2), Ribeiro JA (1,2) and Sebastião AM (1,2)
(1) Institute of Pharmacology and Neurosciences, Faculty of Medicine, and (2) Unit of
Neurosciences, Institute of Molecular Medicine, University of Lisbon, Portugal
LTP is facilitated by exogenous BDNF, an action more evident when LTP is evoked by
weak #-burst stimuli that also favors LTP in aged animals. Thus, we evaluated if the
enhanced LTP in aged rats could be related to changes in endogenous BDNF effect.
Hippocampal LTP was induced by a #-burst protocol. Morris water maze (MWM) was
used to evaluate hippocampal dependent memory.
LTP was significantly higher in hippocampal slices from 36-38 and 70-80week-old rats,
when compared to LTP in slices from younger rats. The scavenger for BDNF and a Trk
phosphorylation inhibitor attenuated LTP in slices from 70-80 but not from 10-15weekold rats. In MWM task, 10-15 and 70-80week-old rats, improved their daily
performance, but aged rats showed a slower learning profile. Significant differences in
latency throughout the acquisition days and an overall effect of age were detected. In
probe test, both age groups spent a significantly higher percentage of time in the
training quadrant. However, young rats spent significantly more time in the training
quadrant than aged rats. These results indicate that the higher LTP observed upon
ageing, which does not translate into improved spatial memory performance, is
consequence of an increase in the action of endogenous BDNF.
Supported by Fundação para a Ciência e Tecnologia, Fundação Calouste Gulbenkian
and EU (COST B-30 concerted action). BDNF was a gift from Regeneron.
37
38
ANALYSIS OF EXCITATORY AND INHIBITORY CONDUCTANCE DYNAMICS DURING
SHARP WAVE RIPPLES IN VITRO
Donoso JR (1,2), Maier N (3), Schmitz D (1,3) and Kempter R (1,2)
(1) Bernstein Center for Computational Neuroscience Berlin, Germany; (2) Institute for
Theoretical Biology, Humboldt Universität zu Berlin, Germany; (3) Neuroscience
Research Center, Charité-Universitätmedizin Berlin, Germany
During slow-wave sleep or immobile resting periods, sharp wave-ripple events (SWR)
can be measured in the local field potential (LFP) of the CA1 region of the
hippocampus of mammals. Information about the temporal structure of inhibitory and
excitatory conductances in a CA1 cell during a SPW-R event would allow us to get
insights about the mechanisms involved in the generation of this complex oscillatory
pattern. Whole-cell recordings enable us to measure the total synaptic input that a
neuron experiences during the extracellular event of interest. In order to probe the
time course of excitation and inhibition, we performed simultaneous recordings of two
nearby pyramidal cells, voltage-clamped at the resting potential of inhibition and
excitation, respectively. Information about the temporal structure of the signals
involved was obtained by analyzing their respective Hilbert transforms in the ripple
band (127-300Hz). Results indicate ripple oscillations are largely dominated by
inhibition. However, an excitatory component is also apparent. In a significant
proportion of SWR, both excitation and inhibition are phase-locked to the LFP ripple
with a consistent phase structure in which excitation leads and inhibition lags the LFP
signal, respectively.
OPTICAL DETECTION OF ACTION POTENTIALS USING NOVEL, OPSIN-BASED
VOLTAGE INDICATORS
Douglass AD, Kralj JM, Hochbaum DR, Engert F and Cohen AE
Harvard University, USA
Reliable optical detection of single action potentials is one of the longest-standing open
challenges in neuroscience. We achieved this goal in cultured neurons using a new
class of genetically encoded voltage indicator. The endogenous fluorescence of voltage
indicating proteins (VIPs) derived from a microbial rhodopsin protein, Archaerhodopsin
3 (Arch), was monitored by epifluorescence microscopy during whole-cell patch clamp
recording. The response time of the indicator was less than 0.5 ms, and membrane
potentials were inferred from the fluorescence with a precision greater than 1
mV/Hz1/2. Single action potentials in mammalian neurons expressing VIPs yielded
clearly detectable bursts of fluorescence. A spike-finding algorithm correctly identified
99.6% of all action potentials in single-trial datasets based on the optical signal alone,
with a false positive rate of 0.7%. The opsin’s light-evoked pumping activity could be
abolished by site-directed mutagenesis, but at some cost to the indicator’s speed. We
further optimized the indicators for in vivo imaging by improving their multiphoton
excitability and overall brightness, and explore their utility in complex tissue
environments. Microbial rhodopsin-based voltage indicators enable optical interrogation
of complex neural circuits, and electrophysiology in systems for which electrode-based
techniques are challenging.
MATHEMATICAL STUDIES IN NEUROSCIENCE: DEVELOPMENTS OF ONE OF THE MOST
SUCCESSFUL COMBINATIONS OF EXPERIMENT AND THEORY
Duarte J and Januário C
ISEL - Engineering Superior Institute of Lisbon, Portugal
With the purpose of understanding the brain dynamics, physiologists have been
extensively studied the generation and propagation of signals for at least the past 100
years.
The most important landmark in these studies is the work of Alan Hodgkin and Andrew
Huxley, who developed the first quantitative model of the propagation of an electrical
signal along a squid giant axon.
This predictive model, considered one of the most successful combinations of elegant
experimental data and comprehensive theoretical hypothesis, motivated the
construction of simpler systems of equations in order to deeply explore the qualitative
behavior of the nerve impulse. This effort led to the collaboration between the
neuroscientist Richard FitzHugh and the computer engineer Jin-ichi Nagumo, resulting
in a model that extracts the essential behavior of the Hodgkin-Huxley equations.
In our work, we present the noteworthy and eye-catching quantitative features of the
Hodgkin-Huxley model and explore the FitzHugh-Nagumo equations as a mean for
understanding the qualitative nature of the nerve impulse propagation, including the
Adrian’s all-or-nothing response and the post-impulse refractory period.
In biology, where quantitatively predictive theories are rare, this work is still another
illustration of the role that mathematics may play in the growing area of neuroscience.
DISTINGUISHING BETWEEN BAYESIAN DECISION MAKING AND DECISION MAKING
BY SIMPLE LINEAR UPDATE RULES
Drugowitsch J, Koechlin E
Institut National de la Santé et de la Recherche Médicale, Ecole Normale Superieure,
Paris, France
Even though humans and animals are able to use both uncertainty and structure of
evidence in decision making, their behaviour is frequently well explained by simple
linear learning rules that do not use this information, such as the Rescorla-Wagner
rule. Here we show by theoretical analysis that, under some very general structural
assumptions on how the observations are generated by some temporally evolving
hidden state, these learning rules correspond to optimal Bayesian inference of this
hidden state in Hidden Markov Models. The assumptions in structure conform to a
volatile environment that changes at each time step with a certain, constant
probability, leading to an unstructured "diffusion" of the hidden state. We show by
simulation that, if these assumptions are violated, the quality of decisions based on
linear rules severely deteriorates when compared to Bayes-optimal decision making.
This insight allows us to distinguish between tasks in which the behaviour and
performance due to utilising these rules is partically indistinguishable from Bayesoptimal performance, and others where Bayes-optimal decision making is clearly
superior. Consequently, this knowledge can guide the design of experiments that allow
us to empirically distinguish between these two forms of decision making.
A CORTICAL SUBSTRATE FOR MEMORY-GUIDED ORIENTING IN THE RAT
Jeffrey C. Erlich, Max Bialek, Carlos D. Brody
HHMI/Princeton University
Anatomical, stimulation and lesion data have suggested a homology between the rat
frontal orienting fields (FOF, centered at +2 AP, ±1.3 ML mm from Bregma) and
primate frontal cortices such as the frontal or supplementary eye fields. We
investigated the functional role of the FOF using rats trained to perform a memoryguided orienting task, in which there was a delay period between the end of a sensory
stimulus instructing orienting direction and the time of the allowed motor response.
Unilateral inactivation of the FOF resulted in impaired contralateral responses.
Extracellular recordings of single units revealed that 37% of FOF neurons had delay
period firing rates that predicted the direction of the rats' later orienting motion. Our
data provide the first electrophysiological and pharmacological evidence supporting the
existence in the rat, as in the primate, of a frontal cortical area involved in the
preparation and/or planning of orienting responses.
39
40
TIME-DEPENDENT BDNF ACTIONS UPON HYPOXIA AND REOXYGENATION
Félix de Oliveira A (1,2), Ribeiro JA (1,2), Sebastião AM (1,2)
(1) Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de
Lisboa, Portugal; (2) Unidade de Neurociências, Instituto de Medicina Molecular,
Universidade de Lisboa, Lisboa, Portugal
Hypoxia, membrane depolarization and massive glutamate release, activate NMDA
receptors. Release of adenosine is another consequence of hypoxia. BDNF cross-talking
with adenosine has important actions upon synaptic plasticity. BDNF excitatory actions
are facilitated by pre-depolarization and BDNF is known to increase NMDA receptor
(NMDAR) activity. We therefore hypothesized that hypoxia could influence synaptic
actions of BDNF. When BDNF was present during hypoxia it impaired recovery of
synaptic transmission, providing that neuroprotection by adenosine is prevented with
an A1R antagonist (DPCPX, 50nM). This impairment is dependent on NMDAR and TrkB
activation since it was absent in the presence of AP5 (50$M, NMDAR antagonist) or
K252a (200mM; tyrosine kinase inhibitor). When BDNF was first applied 30 minutes
after reoxygenation it enhanced synaptic transmission (19±2.7%, n=8). This
enhancement is dependent on A2A and TrkB receptors (prevented by 100nM
ZM241385, A2AR antagonist) and K252a, but independent of NMDA or A1 receptors
(remains in the presence of AP5 or DPCPX). These results disclose a time-dependent
modulation by BDNF upon hypoxia: if present throughout hypoxia, it impairs recovery
of synaptic transmission, an action probably resulting from NMDA receptor activation.
After hypoxia, BDNF enhances synaptic transmission, which might result from A2AR
activation by adenosine released during hypoxia.
ALTERED GENE EXPRESSION AFTER ALC TREATMENT IN A MICE MODEL OF
EXPOSURE TO METHAMPHETAMINE
Fernandes S (1,2), Bravo J (1,2), Cunha L (1) and Summavielle T (1)
(1) Instituto de Biologia Molecular e Celular, Portugal; (2) ESTSP-IPP, ATC-APCT,
Portugal
Introduction: Acetyl-L-carnitine (ALC) is a natural occurring compound that easily
diffuses across biological membranes. Besides its role in fatty acids transport to
mitochondria, ALC has been reported to be protective in several conditions and in
different systems, evidencing that there are most probably other pathways involved in
the action of ALC. In accordance, we have recently demonstrated that ALC pretreatment confers effective neuroprotection against MDMA-induced neurotoxicity.
Objectives: Based on our previous results we aim to understand the possible impact of
ALC over membrane permeability. We used a mice model of exposure to
methamphetamine (METH) to induce striatal toxicity and evaluate the protective role of
ALC. Upon on its dopaminergic toxicity, METH is known to transiently increase
permeability. PCRarrays for the PI3K-AKT signaling pathway (84 genes) were used to
assess altered gene expression in different conditions.
Results: Our results evidenced altered gene expression for IGF1, PABPC1, PRKCB, JUN,
MAPK8, PIK3cg, among others, which is in agreement with our expectations that ALC
may be involved in regulating cell permeability processes.
Conclusion: Loss of permeability control is the hallmark of many pathologies,
understanding the role of ALC at this level, would allow its use in many clinical
conditions.
BEHAVIORAL ROLE OF FAR-PROJECTING A11-TYPE DOPAMINERGIC NEURONS IN
ZEBRAFISH LARVAE
Fernandes AM (1), Beddows E (1), Bergeron S (2), Burgess HA (2), Arrenberg A (1),
Driever W (1)
(1) Developmental Biology, University of Freiburg, Germany; (2) Unit on Behavioral
Neurogenetics, NICHD, USA
We use genetic approaches in zebrafish to investigate development and function of
A11-type DA neurons and their involvement in modulating neural circuits.
The development of specific groups of posterior tubercular and hypothalamic DA
neurons depends on Otp transcription factor activity in zebrafish as well as in mouse,
which revealed the evolutionary conservation of these A11-type DA neurons. Otpdependent DA neurons establish far-ranging descending hindbrain and
diencephalospinal projections, ascending projections to the telencephalon and local
endohypothalamic projections. We hypothesize A11 neurons are the source of DA
neuromodulation of locomotion in zebrafish. To address this question, we generated
double mutants inactivating both otpa and otpb genes, resulting in larvae which lack all
far-projecting DA neurons. Furthermore, we use selective expression of Nitroreductase
and metronidazole-mediated cell ablation to eliminate defined DA groups. We analyzed
potential changes in motor behavior in DA neuron depleted zebrafish larvae using
behavioral assays. DA neuron depleted larvae showed a significant reduction in
prepulse inhibition as well as other behavioral changes. These studies contribute
towards the understanding of the funtion of Otp-specified neurons in modulating
locomotion in larval zebrafish. The combination of different levels of systems analysis
should enable us to link cellular developmental mechanisms and neural circuit function.
PATHWAY SPECIFIC MICRO-LFPS REVEAL FUNCTIONAL CONNECTIVITY AND
ONGOING PLASTICITY IN CA3 INPUT TO CA1
Fernández-Ruiz A (1), Makarov VA (2), Benito N (1) and Herreras (1)
(1) Cajal Institute – CSIC, Madrid, Spain; (2)Faculty of Mathematics, Universidad
Complutense, Madrid, Spain
Information within neuronal networks flows on a sparse code, thus population changes
may report inadequately the distributed transfer between units. Local field potentials (LFPs)
contain an important amount of these data but they are difficult to decompose and
interpret, which has limited their use to the study of synchronous or rhythmic patterns of
activity. However irregular asynchronous activity is predominant in LFPs in the activity of
the neurons and populations in cortical structures.
Using innovative mathematical techniques we resolved ongoing LFPs recorded in the
anesthetized rat hippocampus with linear multielectrode arrays into several major
contributions of stratified LFP-generators [J Comput Neurosci. 29:445, 2010; Neurophysiol.
104:484, 2010]. Pathway-specific LFPs can be reconstructed and their fine temporal
dynamics studied. We here checked the presynaptic identity and temporal accuracy of the
ongoing population Schaffer input to the CA1 pyramidal population and explored its
temporal, spatial and plastic features.
We found that Schaffer-specific LFPs are composed of elementary micro-fEPSPs fired by
presynaptic functional units. Their temporal series served to identify connected cell pairs
and evidenced that CA3-triggered micro-fEPSPs are effective in firing CA1 pyramids and
interneurons without the concurrence of additional inputs. We also present first time
evidence for ongoing long-term plasticity visible on raw LFPs and cell-cell connections. The
possibility of matching the firing of pre and postsynaptic units through their mediating
synaptic currents obtained by pathway-specific microLFPs fills a gap to study ongoing
dynamics in pathways that use sparse coding of information.
41
42
THE ROLE OF OCTOPAMINERGIC NEURONS IN APPETITIVE OLFACTORY LEARNING
AND MEMORY IN DROSOPHILA MELANOGASTER
Clara Howcroft Ferreira (1,2), Paul Overton (1), Gero Miesenbock (1)
(1) Centre for Neural Circuits and Behaviour, University of Oxford, United Kingdom; (2)
International Neuroscience Champalimaud Doctoral Programme, Portugal
Olfactory conditioning has been extensively studied in Drosophila melanogaster, with
the ease of genetic manipulation and small nervous system enabling the discovery of
many conserved mechanisms of learning and memory. The neuronal and molecular
pathways underlying aversive conditioning are relatively well known, and optogenetic
stimulation of dopaminergic neurons in the presence of an odour has recently been
shown to effectively implant an aversive olfactory memory, localizing the source of
aversive reinforcement to a cluster of 12 cells.
It is hypothesized that the circuits and molecular players are similar during appetitive
learning, with the reinforcement signal being conveyed by octopaminergic (OA)
neurons, which comprise 70-100 cells organized in 5 main clusters. Since genetic
access to OA neurons is limited, their role has not been unequivocally determined, nor
has the cluster involved in appetitive olfactory learning and memory been determined.
In order to access the full population and individual clusters of OA neurons in the fly
brain I am targeting the TBH gene, responsible for octopamine synthesis, through
enhancer cloning, homologous recombination and BAC recombineering. I will then use
targeted inactivation and optogenetic stimulation to establish the requirements for
different OA clusters in behaving flies, using an appetitive learning and memory assay.
HOMOEOSTATIC ACTIVITY REGULATES SYNAPTIC ACCUMULATION OF NMDA RECEPTORS
INDEPENDENTLY OF GLUN1 SPLICE VARIANT
Ferreira JS (1), Rooyakkers A (2), She K (2), Ribeiro L (1), Carvalho AL (1),
Craig AM (2)
(1) Center for Neuroscience and Cell Biology and Department of Life Sciences, University of
Coimbra, Coimbra, Portugal; (2) Brain Research Centre and Department of Psychiatry,
University of British Columbia, Vancouver, Canada
NMDA receptors are calcium-permeable ionotropic receptors that detect coincident
glutamate binding and membrane depolarization and are essential for many forms of
synaptic plasticity in the mammalian brain. The obligatory GluN1 subunit of NMDA
receptors is alternatively spliced at multiple sites, generating forms that vary in N-terminal
N1 and C-terminal C1, C2 and C2' cassettes. Based on expression of GluN1 constructs in
heterologous cells and in wild type neurons, the prevalent view is that the C-terminal
cassettes regulate synaptic accumulation by homeostatic activity blockade. Here, we tested
the role of GluN1 splicing in regulated synaptic accumulation of NMDA receptors by
lentiviral expression of individual GluN1 splice variants in hippocampal neurons cultured
from GluN1 (-/-) mice. High efficiency transduction of GluN1 at levels similar to
endogenous was achieved. The N-terminal N1 cassette and the C1 C-terminal cassette did
not affect the synaptic levels of GluN1, whereas the C2’-containing GluN1 subunits are
more abundant at the synapse than those containing the C2 cassette. Surprisingly, all
GluN1 splice variants tested, containing or lacking N1, C1, C2 or C2' cassettes, exhibited
increased synaptic accumulation with chronic blockade of NMDA receptor activity. These
results indicate that the major mechanism mediating homeostatic synaptic accumulation of
NMDA receptors occur independently of GluN1 splice isoform.
This work was supported by Canadian Institutes of Health Research (CIHR) MOP-69096
(A.M.C.) and by the Portuguese Foundation for Science and Technology (FCT) PTDC/BIABCM/71789/2006 and PTDC/SAU-NEU/099440/2008 (A.L.C.).
43
COOPERATION BETWEEN THALAMIC AND CORTICAL INPUTS TO THE LATERAL
AMYGDALA (LA) NUCLEUS
Rosalina Fonseca
Neurobiology of Action, Champalimaud Neuroscience Programme
The knowledge of anatomically distinct input pathways, identifiable cell types and replicable
effects of amygdala lesions on fear conditioning, has made the amygdala an exceptionally
good model to understand the relationship between synaptic plasticity and learning. The
leading cellular model underlying fear conditioning is a form of Hebbian long-term
potentiation (LTP), induced by the association between the neutral conditioned stimulus (CS)
and the unconditioned stimulus (US). A large body of evidence have implicated the lateral
nuclei of the amygdala (LA) as the site where the auditory thalamic and auditory cortex
projections (CS) are associated with the noceciptive input (US). However, the cellular and
molecular mechanisms underlying this associative LTP induction are still a matter of debate.
General mechanisms for induction of LTP in the amygdala have been reported, implicating
MAPK and PKA activation as well as the requirement on de novo protein synthesis. In the
hippocampus, Schaffer collateral synapses, it was demonstrated that different input
pathways can interact over long periods of time after induction of plasticity, either positively synaptic cooperation - or negatively – synaptic competition. Both these phenomena are
based on an activity-dependent redistribution of proteins inside the presumably post-synaptic
cell. The demonstration of such phenomenon in amygdala synapses would be of utmost
relevance due to prolonged integration time that usually occurs when an animal learn to
establish an association between the CS and US.
To test this, we have performed whole cell patch clamp on LA pyramidal cells while
stimulating defined cortical and thalamic projections. We present here the first evidence of
synaptic cooperation in amygdala synapses. L-LTP induction by strong stimulation of the
thalamic projection is sufficient to convert an E-LTP induced by a weak stimulation of a
cortical pathway. As for Schaffer collateral synapses, synaptic cooperation is dependent on
protein synthesis. Cortical E-LTP can be converted into L-LTP if thalamic synapses are
strongly stimulated with an interval of 30 minutes.
Interestingly, cooperation between a weakly stimulated thalamic input and a cortical strong
stimulated input only occurs within a much shorter time interval.
Thalamic E-LTP is only converted into L-LTP by subsequent strong cortical stimulation if the
interval between weak thalamic and strong cortical stimulation is reduced to 7,5 minutes.
We are currently exploring the molecular mechanisms that might underlie this phenomenon.
44
EFFECTS OF SELECTIVE DELETION OF FOXP2 ON THE LEARNING AND PERFORMANCE
OF RAPID MOTOR SEQUENCES
Catherine A. French (1), Xin Jin (2), Simon E. Fisher (3) and Rui M. Costa (1)
(1) Champalimaud Neuroscience Programme at Instituto Gulbenkian de Ciência,
Oeiras, Portugal; (2) Section on In Vivo Neural Function, Laboratory for Integrative
Neuroscience, Bethesda, USA; (3) Language and Genetics Department, Max Planck
Institute for Psycholinguistics, the Netherlands
Mutations in the FOXP2 gene cause impaired speech development and linguistic deficits,
which have been best characterised in a large pedigree called the KE family. Affected
individuals have difficulty mastering the sequences of orofacial motor movements
necessary for fluent speech, a feature which has been proposed to be a core deficit of the
disorder. Other expressive and receptive problems in both oral and written language are
also present. The FOXP2 protein functions as a transcription factor and is highly similar in
many vertebrate species. It also shows conserved expression and is particularly enriched in
the cortico-striatal and cortico-cerebellar circuits required for sensorimotor integration and
motor-skill learning.
Mice carrying an identical mutation to that of the KE family (Foxp2-R552H/+) have motorskill learning deficits and lack striatal long-term depression. We recently recorded striatal
activity in these animals in vivo during training on the accelerating rotarod. Mutants were
found to have an abnormally high ongoing firing rate which was negatively modulated
during skill acquisition, starkly contrasting with the positive modulation seen in control
animals. Changes in the temporal coordination of striatal activity were also evident in
mutants.
We are now using an operant task to investigate in detail the ability of Foxp2-R552H/+
mice to learn and perform rapid motor sequences. We first train mice on a schedule where
a food reward is delivered after 8 lever presses. After 12 days a time constraint is added,
and the sequence of 8 presses must be completed at increasingly high speeds to obtain
the reward. We are examining the microstructure of the behaviour during this task in order
to dissect the nature of the motor-skill deficits in these animals. The performance of
Foxp2-R552H/+ mice is compared with that of Foxp2-S321X/+ mice (the S321X allele
yields no detectable protein). We also trained mice with selective deletion of Foxp2 in the
cortex, striatum and cerebellum (using Emx1-Cre, Rgs9-Cre and L7-Cre respectively). Early
results indicate that mice with homozygous conditional deletion in the latter two areas
show motor-skill deficits.
TEMPORAL AND SPATIAL ASSEMBLY OF EXTRACELLULAR MATRIX IN THE BRAINSTEM
OF CHICKEN EMBRYO
Gaal B (1), Kecskes Sz (2), Matesz K (1,2)
(1) Department of Anatomy, Histology and Embryology, Medical and Health Science
Center, University of Debrecen, Debrecen, Hungary; (2) HAS-UD Neuroscience
Research Group, Debrecen, Hungary
Right after hatching, the young chicken (Gallus domesticus L.) can walk, see, chirp,
and feed, as precocial avians do. These behavioural actions require the early
development of CNS areas responsible for basic motor actions, sensory functions and
homeostasis. Previous studies also revealed, that macromolecules of the extracellular
matrix (ECM) around neurons highly influence their activity, and vice-versa.
The aim of this study is to investigate the development of ECM assembly around
neurons related to motor coordination, in the brainstem of chicken embryos.
We gained chicken embryos by aborting incubation at certain developmental stages.
After fixation, paraffin embedding and sectioning, on the slides histochemistry and
immunohistochemistry was performed for ECM components present: Cat-315, HAPLN1,
WFA and b-HABP. Visualization was by DAB reaction.
Strong HA and aggrecan condensation was seen from E7 stage on, in inferior olive,
cerebellar nuclei, visuomotor, vagus, hypoglossus and two vestibular nuclei, and
hypothalamus-pituitary complex. WFA showed in vestibular and hypoglossus nuclei,
and reticular formation. HAPLN1 showed in none.
These findings suggest that the strongest ECM first appeared at areas responsible for
posture and gaze, feed, homeostasis, motor and psychomotor, and sensory functions,
which might be the character of precocial birds.
Supported by: MTA TKI 242, OTKA K67641.
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46
SOCIAL AND COGNITIVE MODULATION OF THE STRESS RESPONSES IN A CICHLID
FISH
Leonor Galhardo (1,2) and Rui F. Oliveira (1,2)
(1) ISPA- Instituto Universitário, Lisboa, Portugal; (2) Social Neuroendocrinology Lab,
Champalimaud Neuroscience Programme, Instituto Gulbenkian de Ciência, Oeiras,
Portugal
Social isolation has been described as a relevant stressor in social species. We
compared cortisol levels of a social cichlid fish under social isolation with those induced
by other social (stable and unstable social groups) and non-social (food, confinement,
ACTH challenge) contexts. Social isolation elicited the highest cortisol levels among all
other stressors, except for the maximum response to the ACTH challenge. Effects of
social isolation on cortisol and androgens were further explored and we found that it
affects hormonal levels in a differential way, according to the previous dynamics of
social interactions. Two different pairs of males were tested. ‘Territorial/non-territorial’
pairs produced a significant cortisol increase in both males when isolated.
‘Territorial/territorial’ pairs did not respond to social isolation. Regardless of previous
group composition, territorial males showed higher levels of 11-ketosterone and
testosterone. When isolated, androgen levels decreased in territorial males and
increased in non-territorial males, becoming leveled in both males.
Regardless of the nature of stressors, their cognitive evaluation is a highly individual
process and, as social factors, it also modulates the stress response. In fish, this was
evidenced by the manipulation of predictability to feeding and confinement events. The
feeding event involved higher levels of anticipatory behaviour and of cortisol in the
predictable group. The confinement event involved more attention to the visual cue
and lower cortisol in the predictable group.
Together, these findings suggest that the fish stress response is modulated not only by
the stressor’s nature, but also by previous social experiences and appraisal of particular
properties of stressors. This fact can strongly contribute to the full understanding of
the hormonal profiles in response to stress.
DENDRITIC MORPHOLOGY ALTERATIONS IN EPILEPSY: A NEUROCOMPUTATIONAL
STUDY
Misael F. García (1), Antônio C. Roque (2)
(1) Laboratório de Sistemas Neurais. Departamento de Psicologia e Educação.
Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo
(FFCLRP-USP); (2) Laboratório de Sistemas Neurais, Departamento de Física e
Matemática, . Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade
de São Paulo
Epilepsy is one of the most devastating and recurrent neuropathologies. In vivo and in
vitro studies had found a correlation between dendritic morphology alterations and this
pathology. Nevertheless, it has not been completely elucidated if there's a causal
relationship, or the possible consequences of these structural changes. Additionally,
the “spine loss paradox” or “epileptic dendrite paradox” associated to these alterations
is yet to be understood. In this paradox, pyramidal neurons with a reduction in
excitatory synapses’ input (due to a loss of spines and total dendritic area),
unexpectedly have a chronically hyperexcitable state. The aim of this study is to
establish if there's some causality between the dendritic alterations observed and this
pathology, and how these modifications could give rise to changes in excitability. We
are constructing a realistic computational model of a neocortical pyramidal neuron, and
evaluating the electrophysiological effects of dendritic alterations like those observed in
epilepsy. Our preliminary results show a strong relationship between dendritic
alterations and electrical activity. Some modifications even lead to an increase in
excitability through a change in biophysical parameters involved in the generation,
integration and propagation of action potentials from the dendritic tree to the soma
and vice versa (backpropagation). Thus, influencing the spatiotemporal dynamics
responsible for the generation of activity of the bursting and even the epileptiform
type. These results suggest a causal relationship and a possible explanation for the
paradox.
TWO PHOTON IMAGING OF LAYERS I TO VI WITH CHRONICALLY IMPLANTED
MICROPRISMS
Nathan B. Gilfoy, Robert N.S. Sachdev, David A. McCormick and Michael J. Levene
Yale University, School of Medicine, and Biomedical Engineering
Neocortical circuits are organized in columns and layers that span ~ 1.5 mm, even in
mice. Traditional 2-photon imaging methodologies are restricted to only the top few
hundred microns. Here we developed two photon imaging methods for chronically
studying neurons in all layers in a cortical column. Wild-type, or genetically modified
Thy1-YFPH and PvCre-ZSGreen adult mice were surgically implanted with 1.5-mm by
1.5-mm microprisms. Headposts and chambers were surgically attached to the skull,
and microprisms were implanted caudal to and within primary somatosensory “barrel”
cortex of adult mice. A custom built multiphoton microscope was employed to monitor
the implant over days, and tracked changes in the neuropil and the tissue surrounding
the prism. Layer 5 pyramidal cell bodies, interneurons, and blood vessels were clearly
visible through the microprism and could be tracked on the day of the implant and
followed in subsequent days post-implantation. Extracellular recording showed normal
rhythmic Up and Down multiunit activity and local field potentials immediately after the
prism implant and in the days following the implant. Multiunit measurements also
showed that cortical neurons responded to whisker stimulation immediately after
implant of the prism, that the response was specific to particular whiskers. Together,
these results demonstrate that prisms can be effective tools for studying anatomical
and physiologic processes in vivo in layers 1-5.
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48
A NEURAL CIRCUIT MODEL OF THE ZEBRAFISH OCULOMOTOR INTEGRATOR:
THEORY AND OPTOGENETIC DISSECTION
Goncalves PJ (1,2,5,6), Arrenberg AB (3,4,6), Baier H (4), Machens CK (1,2,5)
(1) Group for Neural Theory, Ecole Normale Superieure, France; (2) INSERM Unite
960, Ecole Normale Supérieure, France; (3) University of Freiburg, Biologie I,
Germany; (4) Department of Physiology, Program in Neuroscience, University of
California, San Francisco, USA; (5) Champalimaud Neuroscience Program, Portugal; (6)
Equally contributing authors
The oculomotor integrator in the hindbrain transforms incoming horizontal eye
movement commands into position signals to maintain stable eye fixations after
saccades. A combination of electrophysiological and theoretical studies have led to the
hypothesis that the integrator operates similar to a line attractor network, so that each
eye position finds its correspondence in a stable firing regime of the integrator. In turn,
system states outside of this stable firing regime are attracted towards it (Seung PNAS
1996,93:13339–44). Since eye movements are thought to move the system state from
one stable position to another, the dynamics outside of the stable firing regime are
normally not observable. Here we show how instantaneous perturbations allow us to
explore the dynamics outside the line. We first suggest several models that account for
previous results, yet differ in their dynamical behavior outside the normal regime,
therefore making distinct predictions regarding instantaneous perturbations. Second,
we perform instantaneous (100 ms) optogenetic perturbations in the larval zebrafish
integrator to identify the correct model. We show that the optogenetic data suggest a
new structure for network models, and conclude with suggestions for further
experiments.
2-PHOTON IN VIVO IMAGING OF CORTICAL CIRCUITRY IN THE AGED BRAIN
Grillo FW, De Paola V
MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, United
Kingdom
As human life expectancy grows it becomes a primary goal to understand the neural
mechanisms of the ageing process, a major risk factor for neurodegenerative diseases
and the cause of physiological cognitive decline. Synaptic plasticity in defined cortical
networks rather than neuronal loss could be a major determinant of such cognitive
decline. By coupling 2-photon microscopy with transgenic mice that express fluorescent
proteins in a subset of neurons it is possible to study the dynamics of cortical circuits in
the intact mammalian brain. This approach has the prospect of revealing synaptic
defects, which would be undetectable from post-mortem fixed material. Here attention
is given to Layer 6 (L6) axonal structural plasticity in the aged mouse cortex. L6 axons
in aged mice (n = 5; >20 months) display similar plastic properties to the same axonal
population in young adults (n = 9; ca 4 months). They display similar bouton density,
survival fraction and turnover (n = 856 boutons, young adult group; n = 406, aged
group), suggesting that synaptic remodelling on this type of axons is not affected by
ageing. Future efforts will focus on studying other types of neurons, synaptic strength
and to correlate synaptic plasticity with cognitive performance.
49
REWARD-DEPENDENT PERCEPTUAL LEARNING OF OBJECTS
Matthias Guggenmos (1,2), John-Dylan Haynes (1), Klaus Obermayer (1), Philipp
Sterzer (1,2)
(1) Bernstein Center for Computational Neuroscience Berlin, Germany; (2) Department
of Psychiatry, Campus Charité Mitte, Charité, Universitätsmedizin Berlin, Germany
Perceptual learning is the improvement in performance on sensory tasks following
practice or repeated exposure. In this behavioral study we investigated perceptual
learning of real-world objects in a backward masking paradigm across multiple days.
We provided the subjects with category-specific reward reinforcement to investigate
perceptual learning as a function of the motivational salience of the stimuli. The
subjects had to recognize briefly presented and backward-masked objects and
received, depending on the object category, either a high or low reward for correct
responses. We show that a) perceptual learning takes place in a category-specific
rather than exemplar-specific manner and b) the recognition performance indeed is
improved for the high-rewarded compared to the low-rewarded stimulus categories.
Our results suggest a mechanism in the brain linking perceptual learning of complex
stimuli and the processing of their motivational salience.
We are currently conducting the experiment inside the fMRI scanner to investigate a)
how the representation of objects in higher-level visual cortex changes under learning,
b) how the information content of fMRI response patterns relates to behavioral
improvement and the parametrized visibility of the presented objects and c) the
interdependence of reward reinforcement and information content of activation
patterns in high-level visual areas.
CHARACTERIZING NOVEL ARG3.1 INTERACTION PARTNERS
Jakob Gutzmann, Guido Hermey and Dietmar Kuhl
Center for Molecular Neurobiology Hamburg (ZMNH)
The immediate early gene Arg3.1 is highly and transiently expressed after neuronal activity
and its mRNA is actively transported into dendrites and spines of neurons with a recent
history of activity. Experiments with Arg3.1 knockout mice demonstrate that Arg3.1 is
crucial for the consolidation of long-term memories in a variety of behavioural paradigms
(Plath et al., 2006). Dynamin2 and Endophilin3 have been described as interaction partners
of the Arg3.1 protein, implicating Arg3.1 in trafficking processes of postsynaptic vesicles
that contain AMPA type glutamate receptors. Yet these interactions cannot fully explain the
observed phenotype of Arg3.1 knockout mice. By Yeast 2 Hybrid analysis we identified two
novel interaction partners of Arg3.1, TMP1 and TMP2. Both are so far uncharacterized
multiple pass transmembrane proteins that can be implicated in vesicle trafficking based on
sequence homology. By expression of tagged versions of TMP1 and TMP2 in different cell
types we demonstrate that both proteins are localized to the endoplasmatic reticulum (ER),
and we show that both proteins are found in the ER of neurons including branches of the
ER in distal tips of dendrites. Topology analysis reveals that the N-termini of both proteins
face the cytoplasm and potentially convey the interaction with Arg3.1. Genomic analysis
and semi quantitative RT-PCR establishes that TMP2 is alternatively spliced resulting in
mRNAs with different 3’-UTRs but encoding identical proteins. One of these transcripts is
induced by neuronal activity in cultured hippocampal neurons. Taken together, our results
indicate that Arg3.1 partakes in the activity regulated dendritic secretory pathway. Further
experiments will be performed to clarify the precise role of TMP1 and TMP2 in the dendritic
ER.
Reference: Plath, N et al. (2006). Arc/Arg3.1 Is Essential for the Consolidation of Synaptic
Plasticity and Memories. Neuron 52, 437-444
50
SELF-INDUCED FEEDBACK DURING TETHERED FLIGHT IN DROSOPHILA
MELANOGASTER
Haberkern H, Bartussek J, Medici V, Fry SN
Institute of Neuroinformatics, ETH/University of Zürich, Switzerland
In Drosophila, tethered flight provides a powerful experimental paradigm to study
numerous aspects of flight physiology and behavior. Tethering has been shown,
however, to affect the wing stroke pattern considerably, raising the question of the
relevance of experiments for realistic flight behavior. It is possible that vibrations of
thin wire tethers brought about by the oscillating flight forces can cause
mechanosensory feedback that is quite similar to the forces sensed by during freeflight maneuvers.
To explore the underlying mechanisms, we experimentally controlled the resonant
frequency of the fly-tether system by systematically varying the tether length. We then
used a laser doppler vibrometer to measure the tether oscillations and from it also the
flies’ reactions to it.
We found that tether length strongly affected the flight frequency, e.g. inducing
prolongued periods of frequency locking or periodically varying frequency. These
effects are also reproducible by attaching the fly to a stiff tether and vibrating it using
a piezo actuator.
Our results show that a mechanical detuning is required to avoid unwanted behavioural
artifacts. At the same time, the developed methods are applied to gain new insights
into the low level flight control mechanisms based on haltere feedback.
EFFICIENT INDUCIBLE PAN-NEURONAL CRE-MEDIATED RECOMBINATION IN SLICK-H
TRANSGENIC MICE
Heimer-McGinn V and Young P
Department of Biochemistry, Cork Neuroscience Group, University College Cork, Cork,
Ireland
Large-scale functional genomics in mice is becoming feasible through projects to
develop conditional knockout alleles for every gene. Inducible neuron-specific gene
knockout in such mice will permit the analysis of neuronal phenotypes while
circumventing developmental defects or embryonic lethality. Here we describe a
transgenic line, termed SLICK-H, that facilitates widespread inducible conditional
genetic manipulation within most populations of projection neurons. In SLICK-H mice,
the Thy1 promoter drives robust and relatively uniform expression of a drug-inducible
form of cre recombinase throughout the peripheral and central nervous system. This
permits efficient induction of cre-mediated genetic manipulation upon tamoxifen
administration in adult mice. Importantly, cre activity in the absence of tamoxifen is
minimal, permitting tight control of recombination. In the present study we catalog in
detail the transgene expression patterns and recombination efficiencies in SLICK-H
mice. Our results highlight the utility of SLICK-H mice for functional genomics in the
nervous system.
51
DISENTANGLING LFPS IN THE ORIGINAL SYNAPTIC SOURCES: VALIDATION BY
REALISTIC LFP MODELING IN A LAMINATED STRUCTURE
Herreras O (1), Makarova J (1), Ibarz JM (2), and Makarov VA (3)
(1) Cajal Institute – CSIC; (2) IRYCIS; (3) Dept. Applied Math. Univ. Complutense,
Madrid, Spain.
Local field potentials (LFPs) are raised by ongoing synaptic currents reflecting the
population output of presynaptic populations converging on a region. These, however,
are hard to discriminate because the unavoidable mixing of currents in the extracellular
space. Recently we decomposed spatial profiles of hippocampal LFPs using
Independent Component Analysis (ICA) (Makarov, J Comput Neurosci. 29, 2010;
Korovaichuk, J Neurophysiol. 104, 2010). We found some generators with stable
spatial distribution consistent with known synaptic pathways. Here we investigated the
robustness of ICA to separate mixed LFP sources and their temporal accuracy. Virtual
LFPs were built with a realistic multineuronal model of the CA1 (Varona, J Neurophysiol
83, 2000) fed with series of synaptic inputs in known somatodendritic locations. ICA
was applied to virtual LFPs and the components compared to original sources. We
tested a wide spatio-temporal spectrum of excitatory and inhibitory synaptic inputs. In
the vast majority of cases ICA discriminated each of the synaptic inputs even when
active membrane domains overlapped heavily, while their temporal dynamics was
accurate to the millisecond. Very weak generators are susceptible to error. In a few
cases we found cross-contamination amongst sources and spurious generators,
typically derived from the mutual interaction of synaptic currents in individual cells and
the complex cell geometry. We conclude that the temporal variation of an LFP source
separated by ICA is a reliable instantaneous correlate (time-varying envelope) of the
total synaptic current generated in target cells by activation of a homogeneous
presynaptic population.
NEURAL CIRCUITS CONTROLLING FEMALE REPRODUCTIVE BEHAVIOR
Dennis Herrmann, Ricardo Silva, Maria Luísa Vasconcelos
Innate Behavior Lab, Champalimaud Neuroscience Program
Evolution equipped Drosophila melanogaster with reliable mechanisms to mediate mate
choice ensuring successful propagation of the species. These mechanisms manifest in
a stereotyped courtship behavior, during which the female is subjected to sensory
modalities presented by the male which influence her decision whether to mate or
not1. These stimuli are processed and integrated by neural networks to yield an innate
behavioral phenotype2. We use a single-pair courtship assay to perform a behavioral
screen of genetically modified nervous systems, allowing us to functionally and
anatomically characterize the circuitry controlling female reproductive behavior. We
prove the principle of our experimental design and show the involvement of Apterouspositive neurons in female receptivity. The results will lead to an understanding of how
neural networks are assembled in order to transform sensory input into behavioral
output.
52
SYNAPTIC CLUSTERING IN RESPONSE TO ACTIVITY AT SINGLE SYNAPSES
Anna Hobbiss, Inbal Israely
Neuronal Structure and Function Laboratory, Chamaplimaud Neuroscience Programme
The morphology and physiology of neurons has been shown to change in response to
activity, regarded as a biological correlate of memory storage. In this project, we
examine the evidence for synaptic clustering, i.e. a tendency for synapses which are
activated at the same time to aggregate together along the dendrite. Initially, we are
examining the endogenous distribution of synapses along dendrites of hippocampal
CA1 neurons in organotypic slice cultures. Our preliminary analyses reveal differences
between the distribution patterns depending on the order of the dendrite (1st, 2nd or
3rd). Secondly, we will look at competition between spines for long lasting plasticity
and determine how newly synthesized proteins are important for this process. We
will uncage glutamate in order to stimulate synapses at specified distances along a
dendrite. A balance between protein sharing and competition during synaptic tagging
and capture would be a mechanism that could enact clustering by selectively
strengthening neighbouring inputs.
EFFECTS OF TARGET PROBABILITY AND RESPONSE SELECTION ON MOTOR-RELATED
OSCILLATIONS
Hodzhev Y, Yordanova J, Nanova P, Lyamova L, Kolev V
Institute of Neurobiology, Bulgarian Academy of Sciences, Bulgaria
Studies of event-related potentials and neuroelectric oscillations have demonstrated
that unexpected or low-probability targets are associated with increased cognitive
processing relative to frequently occurring targets. It is not well understood, however,
whether and how target probability modulates neural processes during response
generation. The objectives of our study were to assess (1) the effects of response
probability on neural oscillations during response production, and (2) the modulation of
probability effects by response selection. Subjects performed auditory simple and
choice reaction tasks (SRT, CRT), in which two types of stimuli were presented
randomly with different probabilities (p=0.15 and p=0.85). Total power and
synchronization of delta, theta and alpha oscillations of response-related potentials
were analyzed. It was found that (1) low-probability targets reduced the power of
posterior alpha oscillations, more strongly in the CRT, whereas fronto-parietal alpha
synchronization was enhanced by high-probability targets. (2) response selection alone
was associated with increased theta synchronization at the left motor cortex, which
remained unaffected by probability. Results demonstrate that during response
generation, oscillatory networks in the alpha range are sensitive to target probability
reflecting a greater functional activation of posterior cortical areas by low-probability
responses and increased synchronization of fronto-parietal areas promoting the
processing of frequent responses.
53
IDENTIFICATION OF NEURAL CIRCUITS THAT PROMOTE AGGRESSION IN
DROSOPHILA MELANOGASTER
Hoopfer ED (1,2), Rubin GM (1), Anderson DJ (2)
(1) Janelia Farm Research Campus, HHMI, USA & California Institute of Technology,
USA; (2) Janelia Farm Research Campus, HHMI, USA
Drosophila melanogaster males engage in a set of stereotyped agonistic interactions
over resources such as food or potential mates. In vertebrates and invertebrates
aggression is strongly influenced by neuromodulatory systems, as well as
environmental factors and social experience. However, the neural circuits that mediate
aggressive behavior, and where and how in this circuitry factor that influence
aggression act, remain largely unknown.
To identify neural circuits involved in aggressive behavior, we developed a highthroughput, automated assay of Drosophila male social behavior that uses machine
vision based software to quantify aggressive and courtship interactions between pairs
of males. Using this system, we screened a large collection of GAL4 lines with sparse
expression patterns in the CNS to identify neurons that promote aggression when
transiently activated using the temperature-sensitive Drosophila TRPA1 channel.
Around 1 percent of the lines show a robust, temperature-dependent, increase in
male-male aggression or male-male courtship. These hits fall into distinct phenotypic
groups based on the subsets of aggressive behaviors that they induce, suggesting that
we may have uncovered neurons that regulate distinct subsets of the aggression
program. Lastly, we describe results of secondary behavioral assays aimed at assessing
necessity of the neurons for aggression, and addressing how these neurons influence
the expression of aggression in different social contexts.
ENRICHED
ENVIRONMENT
DOWN-REGULATES
MACROPHAGE
MIGRATION
INHIBITORY FACTOR AND INCREASES PARVALBUMIN IN THE RAT BRAIN AFTER
ISCHEMIC STROKE
Inácio AR, Ruscher K and Wieloch T
Experimental Brain Research, Department of Clinical Sciences, Lund University, Sweden
Housing rodents in an enriched environment promotes the recovery of neurological
function after focal cerebral ischemia, an effect that has been attributed to neural
plasticity. Previously, we found that exposing rats to an environmental enrichment
subsequent to permanent middle cerebral artery occlusion (pMCAo) attenuates brain
inflammation. Here, we determined if an enhanced behavioral performance five days
after pMCAo, in rats, was associated with changes in the cerebral expression of
macrophage migration inhibitory factor (MIF), an upstream regulator of inflammation.
In the brains of sham-operated rats, MIF-immunoreactivity (MIF-IR) was evident in
neurons, particularly throughout the neocortex, and cortical parvalbumin-positive cells
exhibited a relatively high MIF-IR. After pMCAo, MIF-IR increased around the infarct
core, where it was found in neurons and astrocytes. Importantly, housing rats in an
enriched environment from day two to day five after pMCAo resulted in a downregulation of MIF, both in the peri-infarct region and ipsilateral cingulate cortex, when
compared to housing rats in standard laboratory cages. This decrease was
accompanied by an increase in the number of parvalbumin-positive cells within the
peri-infarct motor-somatosensory cortex. Our results suggest a role for MIF and
parvalbumin/parvalbumin-positive cells in functional recovery after ischemic stroke.
54
MODULATION OF GABA UPTAKE BY P2Y1 METABOTROPIC PURINERGIC RECEPTOR IN
RAT CORTICAL ASTROCYTES
Jacob Joaquim P, Vaz Sandra H, Ribeiro Joaquim A, Sebastião Ana M
Institute of Pharmacology and Neurosciences, Faculty of Medicine, and Unit of
Neuroscience, Institute of Molecular Medicine, University of Lisbon, Portugal
Astrocytes are involved in the termination and regulation of GABA spill over, into the
extrasynaptic space, mainly through GABA transporters GAT-1 and GAT-3. These GATs
can be regulated by PKC pathway, which is also involved in the form of astrocytic
communication through Ca2+-waves. Ca2+-waves can be induced by P2Y1 G proteincoupled receptors, through the PLC-PKC pathway. So, the aim of this work was to
assess if activation of Ca2+ waves can alter GABA transport in astrocytes.
Brief pressure application of ATP (P2 agonist) and 2-MeSADP (P2Y1,12,13 agonist)
caused a concentration-dependent increase of [Ca2+]i, that was almost completely
abolished using non-selective P2R antagonists; blocking P2Y1R inhibits the response to
2-MeSADP, and this increase of [Ca2+]i was due primarily to the release of Ca2+ from
intracellular stores.
Application of ATP, for 1 minute, inhibits [3H]-GABA uptake through GAT-1 and GAT-3,
this effect is more pronounced when applying the P2Y1R stable agonist 2-MeSADP.
Moreover, when intracellular Ca2+ mobilization and PLC pathway were blocked, 2MeSADP no longer induced an inhibition on uptake.
In conclusion, brief activation of P2Y1R in astrocytes triggers Ca2+ waves and inhibits
GABA transport into astrocytes, suggesting that the two main astrocytic functions can
be related to control extracellular GABA levels.
A MODEL OF INHERITANCE OF HIPPOCAMPAL PHASE PRECESSION
Jorge Jaramillo (1,2), Robert Schmidt (1,2), Tiziano D'Albis (2) and
Richard Kempter (1,2)
(1) Institute for Theoretical Biology, Humboldt Universitaet zu Berlin, Germany, (2)
Bernstein Center for Computational Neuroscience, Berlin, Germany
Hippocampal place cells in rodents exhibit phase precession, the advancement of a
neuron's firing phase with respect to theta oscillations (4-12 Hz) in the local field
potential. Phase precession is observed during exploratory behavior, and its functional
role has been linked to memory and spatial navigation. An open question is the origin
of phase precession. Models that attempt to explain the phase precession observed in
Hippocampal area CA1 in particular, assumed that it is generated intrinsically there.
Through computational modeling we investigated an alternative possibility, namely the
possibility of the CA1 region inheriting phase precession from the CA3 region. The
inheritance model consists of a feedforward excitatory input from a subset of the CA3
place cell population onto the CA1 region via the Schaffer Collaterals. We were able to
simulate the CA1 membrane potential and calculate its analytical form as a function of
the model parameters, including the firing rate within a CA3 place field and excitatory
postsynaptic potentials in a CA1 cell. The resulting membrane potential trace is
consistent with intracellular recordings of CA1 place cells (Harvey et al, 2009). The
results suggest that CA1 can inherit phase precession from CA3 and that inheritance
may be a mechanism to coordinate these two regions of the hippocampus.
55
MEDITATION: HOW DOES IT AFFECT THE BRAIN?
Hope A. Johnson and Zach F. Mainen
Champalimaud Neuroscience Programme, Fundação Champalimaud, Lisboa, Portugal
Meditation is a practice of self-directed introspection with the aim of moving beyond
the reflexive “thinking” mind, and gaining an increased awareness of one’s perceptual,
emotional and cognitive processes. The practice may refer to a broad variety of
techniques that, like other cognitive and/or physical training activities such as learning
to speak language or play a musical instrument, might be expected to result in
modified cognitive functioning via classical plasticity mechanisms. Previous studies
have indeed demonstrated modest alterations in attention, perceptual discrimination
and processing, psychomotor tasks, and emotional response. However, it remains
unclear whether meditation practice enacts an experience-specific change in networkor modality-specific function that is related to the chosen technique, or if it effects a
global change in brain functioning or behavioral state. To address this, we will compare
the performance in various tests of cognitive and perceptual abilities of practitioners of
two different meditative techniques and non-practitioner controls. Tests will be used
that target the specific training techniques of the two types of meditation and, based
on this, would be expected to result in different performance profiles in the two
practitioner groups as well as between the practitioners and controls. After identifying
altered behavioral function in, the long-term goal is to understand which brain areas
are undergoing modifications as a result of meditative practice.
SPATIAL DISTRIBUTIONS OF GABA RECEPTORS AND LOCAL INHIBITION OF SPIKEINDUCED CA2+ TRANSIENTS INVESTIGATED WITH GABA UNCAGING IN THE
DENDRITES OF CA1 PYRAMIDAL NEURONS
Kanemoto Y (1,2), Matsuzaki M (2), Morita S (2), Momotake A (3) and Kasai H (2)
(1) University College London, UK; (2) University of Tokyo, Japan; (3) University of
Tsukuba
GABA-mediated inhibition in the dendrites of CA1 pyramidal neurons was characterized
by two-photon uncaging of BCMACM-GABA and one-photon uncaging of RuBi-GABA.
We found that GABAA-mediated currents elicited at the branch points of the apical
dendritic trunk were approximately two times larger than those elsewhere in the
dendrite. We also examined the inhibitory action of the GABA-induced currents on
Ca2+ transients evoked with a single bAP in oblique dendrites.
56
SYNCHRONOUS NETWORK ACTIVITY FLUCTUATIONS IN THE RODENT PREFRONTAL
CORTEX DURING PERIODS OF BEHAVIORAL UNCERTAINTY
Mattias P. Karlsson, Dougal G.R. Tervo, and Alla Y. Karpova
Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn Virginia
The prefrontal cortex has been shown to encode a diverse set of contextual and
behavioral parameters related to decision making. Yet, the receptive field of any
individual neuron will often correlate only with a very restricted subset of these
parameters, and relatively little is known about how these distinct patterns are
combined on the population level. To what degree do these diverse codes act in unison
when animals transition between different behavioral strategies? Individual neurons in
the prefrontal cortex are capable of abruptly modifying their activity in response to
changing behavioral demands. One prediction of a combined representation hypothesis
would be that abrupt single-cell changes in activity would coincide with larger, unified
network-level transitions. Here we investigate this hypothesis using large ensemble
recordings from the medial prefrontal cortex of freely behaving rats. We observe
cohesive and abrupt changes in ensemble task representation, often times reflected as
large synchronized fluctuations in the receptive fields of the majority of simultaneously
recorded cells. These fluctuations cannot be easily attributed to simple changes in the
current sensory motor experience, but instead tend to occur during transitions in
behavioral strategy. The best behavioral predictor of the observed dynamics is a switch
from the main, largely exploitative policy to a more exploratory behavior. This
phenomenon may be a signature of network-wide learning rate increases occurring at
behaviorally advantageous moments in time.
AN IMBALANCING ACT: GAP JUNCTIONS REDUCE THE BACKWARD MOTOR CIRCUIT
ACTIVITY TO BIAS C. ELEGANS FOR FORWARD LOCOMOTION
Taizo Kawano, Michelle D. Po, Shangbang Gao and Mei Zhen
Samuel Lunenfeld Research Institute, University of Toronto, Canada
A neural network can sustain and switch between different activity patterns to execute
multiple behaviors. Monitoring the decision-making for directional locomotion through
motor circuit calcium imaging in behaving C. elegans, we reveal that C. elegans
determines the directionality of movements by establishing an imbalanced output
between the forward and backward motor circuits, and alters directions by switching
between these imbalanced states. We further demonstrate that interneurons modulate
endogenous motoneuron activity to establish the output imbalance. Specifically, the
UNC-7 and UNC-9 innexin-dependent command interneuron-motoneuron coupling
prevents a balanced output state that leads to movements without directionality.
Moreover, they act as shunts to decrease the backward circuit activity, establishing a
persistent bias for the high forward circuit output state that results in C. elegans’
inherent preference for forward locomotion.
57
DISTRIBUTION OF TRIGEMINAL AFFERENT TERMINALS ON FUNCTIONALLY
DIFFERENT GLOSSOPHARYNGEAL AND VAGUS MOTONEURONS IN THE FROG, RANA
ESCULENTA
Szilvia Kecskes, Botond Gaal, Klara Matesz, Andras Birinyi
Department of Anatomy, Histology and Embryology, University of Debrecen, Medical
and Health Science Center, Debrecen, Hungary
Frog’s prey-catching behavioral pattern consists of sequence of coordinated activity of
different muscles corresponding to stages of feeding. Snapping of prey object
stimulates the trigeminal afferent terminals of the oral cavity and pharynx which
initiates contraction of muscles innervated by the glossopharyngeal and vagus (IX-X)
nerves. The aim of our experiments was to examine whether the trigeminal afferent
fibers establish direct connections with the motoneurons of glossopharyngeal and
vagus nerve.
In anaesthetized animals the trigeminal nerve and the common root of
glossopharyngeal-vagus and accessory (IX-X-XI) nerves were simultaneously labeled
with fluorescein dextran amine (trigeminal nerve) and tetramethylrhodamine dextran
amine (IX-X-XI).
Close appositions between the trigeminal afferent fibers and IX-X motoneurons of the
ambiguus nucleus were detected with confocal microscopy. In order to show the
spatial distribution of these connections within the functionally different subdivisions of
the ambiguus nucleus, Neurolucida reconstruction of the brainstem was made to
detect the position of trigeminal afferents on the dendrites and perikarya of the IX-X
motoneurons. To detect the terminals of the mesencephalic trigeminal nucleus, related
to the proprioceptive innervations of the oral cavity, the Gasserian ganglion was
destroyed before the fluorescent labeling.
The possible monosynaptic connections between the trigeminal afferents and IX-X
motoneurons presented here may be one of the morphological substrate of a very
quick response of the frog during the prey-catching behavior.
This work was supported by OTKA K 67641 and MTA-TKI 242.
EFFECTS OF AMYLOID BETA INJECTIONS ON NEURAL FUNCTIONS IN THE LARVAL
ZEBRAFISH
Kettunen P, Sundell J and Zetterberg H
Institute of Neuroscience and Physiology, University of Gothenburg, Sweden
Alzheimer’s disease is generally thought to be caused by an accumulation of the 42 amino
acid isoform of amyloid beta, A beta(1-42), a cleavage product of amyloid precursor
protein. In the nervous system, A beta is suggested to induce synaptic dysfunction and cell
death, leading to memory deficits. We have started to use the zebrafish (Danio rerio) to
further investigate the molecular pathogenesis underlying Alzheimer’s disease.
To test the effects of A beta on cell death and memory function, synthetic A beta(1-42)
peptides were incubated for oligomerization and then injected into the brain of 2-day-old
zebrafish embryos. The learning of the startle response was tested the next day using
behavioral experiments. The resulting cell death was monitored in vivo using acridine
orange staining.
Our results indicate that A beta(1-42) peptides induce a higher degree of cell death in vivo,
in comparison with control peptides. Additionally, A beta(1-42) peptide injection blocked
learning of the startle response.
These data suggest that the zebrafish can be used to model A beta-induced neuronal
dysfunction, which opens up for mechanistic studies of A beta toxicity in Alzheimer’s
disease, as well as drug screening projects.
58
IDENTIFICATION OF SIGNALLING PATHWAYS GOVERNING SYNAPSE DEVELOPMENT
AND MAINTENANCE IN DROSOPHILA
Kieweg ID and Pielage J
Friedrich Miescher Institute for Biomedical Research, Switzerland, Basel
Synaptic connections are the basis for the formation of functional neuronal circuits.
During development these circuits can be refined through the selective disassembly of
previously functional synapses. In addition, activity-dependent processes, like learning
and memory, can selectively alter synaptic connectivity. Furthermore, studies in
vertebrate disease models have shown that the loss of synaptic connections is central
to most if not all neurodegenerative diseases. Despite this importance of synapse
assembly and disassembly, little is known about the molecular mechanisms underlying
these processes.
We are using the neuromuscular junction (NMJ) of Drosophila larvae as a model
system to investigate synapses development in response to internal and external
stimuli. Using a high resolution morphology assay, we previously identified a
presynaptic molecular network consisting of Spectrin, the adaptor molecule Ankyrin2
and the actin-capping molecule Hts/Adducin necessary for synapse formation and
stability. This network could provide a platform for signalling pathways to control
different aspects of synapse development.
To identify novel regulators of synapse formation and maintenance, I performed an
RNA interference (RNAi)-based genetic screen targeting 133 signalling molecules.
Here, I will present initial results of this screen demonstrating the importance of
different signalling pathways for the control of NMJ development.
REQUIREMENT OF SYNAPTIC PLASTICITY FOR PRECISE SPATIAL AND TEMPORAL
FIRING OF HIPPOCAMPAL PLACE CELLS
Takuma Kitanishi, Mehdi Fallahnezhad, Naomi Kitanishi, Ayumu Tashiro
Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory,
Norwegian University of Science and Technology, Trondheim, Norway
Studies have suggested roles of synaptic plasticity in hippocampal place cells.
However, whether synaptic plasticity in place cells themselves mediates their spatial
firing is not clear because of behavioral and/or cognitive deficits associated with the
experimental manipulations. We devised a versatile approach to monitor activity of
manipulated neurons without global changes in brain functions and behaviours by
combining a multi-tetrode recording with micro genetic manipulation mediated by
adeno-associated viral vectors (AAV). To block synaptic plasticity, AMPA receptor
trafficking was interfered with by a dominant-negative mutant, GluR1-c-tail. AAV
vectors achieved pyramidal cell-selective transduction in a small portion of the rat
hippocampal CA1 area. A within-subject control design was taken by injecting control
or plasticity-blocking vector (expressing eGFP or eGFP-GluR1-c-tail respectively) into
each hemisphere and by bilaterally monitoring neuronal activity. We found that GluR1c-tail inhibits rapid formation of stable spatial firing in open field and linear track
environments. Furthermore, impairment was observed in temporal firing pattern of
place cells during a type of Gamma oscillation that is thought to originate from the CA3
area. Thus, synaptic plasticity is required for precise spatial and temporal firing of place
cells, supporting the hypothesis that place cells store spatial information through their
own synaptic plasticity.
59
DISSECTING THE SENSORY BASIS OF DROSOPHILA GRAVITAXIS
Kladt N and Reiser M
Janelia Farm Research Campus (HHMI), US
Drosophila shows a robust negative gravitaxis response, i.e. flies have a tendency to
walk up if no other cues are present. Although this behavior is regularly used as a
behavioral control, we do not understand which sensory structures flies use to sense
gravity. Recently, it was shown that a subset of the antennal Jonston’s organ is
important for gravitaxis as observed in a counter-current assay.
We have conducted a thorough behavioral analysis of flies walking in an arena with
varying inclinations and lighting conditions. Using this setup, we were able to show
that wildtype flies show gravity specific responses starting from angles of about 2
degrees with maximum behavioral responses seen from angles of 30 degrees on. We
then went on to study the sensory basis of this behavior. Our results indicate, that
although the Johnston’s organ has a clear effect on gravitaxis, this effect is probably
not caused by a loss of the gravity sense per se.
If the antennae are not the main gravity sensing structure, what other structures might
be involved? First results indicate a major function for leg sensory structures and we
are currently investigating which sensory structure is actually used to detect gravity.
PLASTICITY OF ORIENTATION PREFERENCE IN MOUSE VISUAL CORTEX
Kreile AK, Bonhoeffer T, Hübener M
Max Planck Institute of Neurobiology, Germany
Orientation preference in the visual cortex develops independently from visual input,
but restricting experience to a single orientation by stripe rearing causes an
overrepresentation of the experienced orientation. This effect could be caused by a
permissive (loss of responsiveness) or by an instructive mechanism (change in
orientation preference).
We stripe reared mice from postnatal day 25 onwards for three weeks with cylindrical
lenses (167dpt) of four different orientations affixed to skull mounted goggles.
Orientation preference was then measured with two-photon calcium imaging, providing
single cell resolution and allowing direct testing of the two hypotheses.
In stripe reared mice, the distributions of preferred orientations showed a clear shift
towards the experienced orientation. The fraction of responsive neurons decreased
slightly, but not significantly. The decrease in responsiveness, however, was not
correlated with the magnitude of the shift in the distribution of preferred orientations in
individual animals. Moreover, in lower layer II/III there was a clear shift towards the
experienced orientation, but no drop in the fraction of responsive neurons.
Thus, the effects of stripe rearing are mediated by diverse mechanisms, but the
change in preferred orientation is largely caused by an instructive process, by which
individual neurons change their preferred orientation.
60
MULTIMERIC ORB2 COMPLEXES MEDIATE LONG-TERM MEMORY IN DROSOPHILA
Krüttner S (1), Stepien B (1), Noordermeer JN (2), Dickson BJ (1), Keleman K (1)
(1) Research Institute of Molecular Pathology (IMP), Vienna, Austria; (2) Leiden
University Medical Centre, Leiden, The Netherlands
Long-term behavioral memory and synaptic plasticity both require new protein
synthesis locally at activated synapses. CPEB proteins have been implicated in this
process. Consistently, the Drosophila CPEB homologue Orb2 is required for long-term
courtship memory.
Here we aim to define the molecular and cellular mechanisms of Orb2 function in longterm memory. We have generated an orb2attP allele, in which we replaced most of its
reading frame with the target sequence for the site specific recombinase PhiC31. This
allowed us to rapidly introduce any desired replacement of the orb2 endogenous locus
to characterize its expression pattern and conduct structure function analysis of its role
in long- term memory.
We have established that Orb2 is specifically enriched in the nervous system. We show
that Orb2A and Orb2B isoform have non-redundant function in long-term memory. The
function of Orb2A is critically dependent on the N-terminal Glutamine stretch, a
putative prion-forming domain. Consistent with the idea of Orb2 having prion-like
functions, we find both isoforms to be involved in formation of aggregates. These
seem to be functional in long-term memory formation, since independent mutations
within the Orb2 coding sequence, each leading to disturbed long-term memory, can
fully complement each other behaviorally.
HIPPOCAMPAL DELTA-THETA DYNAMIC DURING CONTEXTUAL FEAR CONDITIONING
Kunicki ACB (1), Machado BS (2), Morya E (3), Ribeiro S (4); Amaro Junior E (2),
Sameshima K (1)
(1) University of São Paulo Medical School, Brazil; (2) Brain Institute, Hospital Israelita
Albert Einstein, Brazil; (3) Alberto Santos Dumont Research Support Association, Brazil;
(4) Universidade Federal do Rio Grande do Norte, Brazil
The hippocampus is important for the formation of contextual memory during the
acquisition of conditioned fear. To investigate brain electrical activity changes related
to learning in a contextual fear conditioning were implanted microeletrodes arrays in
the hippocampal CA1 region. One week after surgery, multi-unit activities were
recorded during the contextual fear conditioning. The animals were placed in
conditioning chamber for 7 minutes. After 2 minutes they were presented with 5
unsigned feet shocks trains. One group was tested 1 day later (recent memory test),
and other group 18 days later (remote memory test). To determine the relation
between brain waves, the hippocampal delta - theta ratio was measured in 2 s
segments in different behaviors (exploratory behavior or freezing). We found that in
freezing, as compared with exploratory behavior, the hippocampal activity occur
predominantly between 2 - 4 Hz (delta band). When compared to animals in freezing
tested 1 or 18 days after training, the animals tested 1 day after showed higher delta theta ratio. The strongest theta activity occurred in exploratory behavioral. The results
suggest that delta - theta dynamics oscillations could reflect demands on information
processing during the learning in a defensive behavior.
PROCESSING OF COMPLEX ODOR MIXTURES IN THE MOTH ANTENNAL LOBE
Kuebler LS (1), Olsson SB (1), Weniger R (1), Schubert M (2), Hansson BS (1)
(1) Department of Evolutionary Neuroethology, Max-Planck-Institut for Chemical
Ecology, Jena, Germany; (2) Department of Neurobiology, FU Berlin, Germany
The world is a cacophony of scent. Yet how do animals decipher these complex
mixtures from a noisy background to recognize a meaningful signal? Our goal is to
reveal mechanisms of complex odor information processing at different levels in the
antennal lobe (AL) of the hawk moth, Manduca sexta. Using a novel multicomponent
stimulus system, we performed intracellular recordings of projection (PNs) and
interneurons (LNs) in an attempt to thoroughly characterize host blend vs. single
component representation and integration properties within single neurons of the moth
AL. To assess the network as a whole, optophysiological studies of the AL were used to
assess calcium activity in response to these same stimuli. We simultaneously measured
projection neuron output in concert with the compound signal dominated by sensory
neuron input across the glomerular array. By comparing odor evoked activity patterns
and response intensities between the two processing levels we could determine the
relative interactions between input and output for complex blends within a single
animal. We show that host blends in the moth olfactory system establish a unique
blend percept separate from individual component identities as early as the first
olfactory processing stage, the antennal lobe.
COMMENSALISM DRIVES DROSOPHILA SECHELLIA ADAPTATION TO A TOXIC HOST
Lavista Llanos S (1), Riemensperger T (2), Birman S (2), Hansson BS (1) and
Stensmyr MC (1)
(1) Max Planck Institute for Chemical Ecology, Germany; (2) Ecole Supérieure de
Physique et de Chimie Industrielles, ParisTech, France.
The evolutionary force that drove the adaptation of Drosophila sechellia to its toxic
host fruit Morinda citrifolia has been so far elusive. D. sechellia is highly specialized in
detecting and coding key components present in Morinda, which in turn influence the
physiology and behaviour of the fly: lack of avoidance to the resistible host toxin and
an enhanced sensitivity and preference to host odours. Concomitantly, these volatiles
and other yet-unknown compounds present in Morinda have a stimulatory effect on
sechellia poor egg-laying. We found that the poor reproductive performance of D.
sechellia on laboratory conditions correlates with altered levels of biogenic amines in
the central nervous system and in the ovary of the fly. Morinda diet stimulates egglaying in D. sechellia and in a D. melanogaster mutant that lacks octopamine.
Moreover, Morinda diet re-established the levels of dopamine in D. sechellia, which in
turn partially rescued D. sechellia egg-laying as dietary supplement. Finally, both its
precursor L-DOPA and dopamine are present in Morinda fruit, detected by HPLC. These
results raise an evolutionary hypothetical scenario where the requirement of biogenic
amines for a most favourable reproductive fitness drove D. sechellia host-shift towards
an obligatory commensalism on the toxic Morinda fruit.
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REDUCED VARIABILITY OF ONGOING AND EVOKED CORTICAL ACTIVITY LEADS TO
IMPROVED BEHAVIORAL PERFORMANCE
Ledberg A (1), Coppola R (2), Bressler SL (3)
(1) Center for Brain and Cognition, Universitat Pompeu Fabra, Barcelona Spain; (2)
Clinical Brain Disorders Branch, National Institute of Mental Health, Bethesda MD, USA;
(3) Center for Complex Systems and Brain Sciences, Department of Psychology, Florida
Atlantic University, Boca Raton, FL, USA
Sensory responses of the brain are known to be highly variable, but the origin and
functional relevance of this variability has remained enigmatic. Variability in sensory
responses limits the information these carry about stimulus properties, and
consequently limits their use in controlling behavior.
To characterize the variability of the sensory evoked responses we analyzed LFPs
simultaneously recorded from multiple cortical areas in two rhesus macaques. The
subjects depressed a lever to begin each trial and shortly thereafter a visual stimulus
appeared. Depending on the stimulus, the subject had to either release the lever or
keep it pressed. The time between trial start and stimulus presentation (foreperiod)
varied randomly from trial to trial. We analyzed LFPs in a short window covering the
early part of the visually evoked potential (VEP).
We show that VEP variability in widespread cortical regions is strongly modulated by
foreperiod duration. As foreperiod duration increases VEP variability decreases.
Furthermore, VEP variability is correlated with ongoing cortical activity at the time of
stimulus onset, suggesting that part of the VEP variability is caused by ongoing cortical
activity. Finally we show that the foreperiod-dependent reduction of mean response
times can be explained by reduction in VEP variability.
ACTIVATION OF SPECIFIC INTERNEURONS IMPROVES V1 FEATURE SELECTIVITY AND
VISUAL PERCEPTION
Lee SH (1, 2), Kwan AC (1), Phoumthipphavong V (1), Dehmobad, D (1), Flannery JG
(1), Masmanidis SC (3), Taniguchi H (4), Huang ZJ (4), Boyden ES (5), Deisseroth K
(6), Dan Y (1,2)
(1) Helen Wills Neuroscience Institute, University of California, Berkeley, US; (2) HHMI,
University of California, Berkeley, US; (3) California Institute of Technology, US; (4)
Cold Spring Harbor Laboratory, US; (5) Massachusettes Institute of Technology, US;
(6) HHMI, Stanford University, US
Inhibitory interneurons are essential components of the neural circuits underlying a
variety of brain functions. In the neocortex, a large diversity of GABAergic interneurons
have been identified based on their morphology, molecular markers, biophysical
properties, and innervation pattern. However, how the spiking activity of each subtype
of interneurons contributes to sensory processing remains largely unknown. Here we
show that optogenetic activation of parvalbumin-positive (PV+) interneurons in mouse
primary visual cortex (V1) sharpens neuronal feature selectivity and improves
perceptual discrimination. Using multichannel recording with silicon probes and
channelrhodopsin 2 (ChR2)-mediated optical activation, we found that elevated spiking
of PV+ interneurons markedly sharpened orientation tuning and enhanced direction
selectivity of nearby V1 neurons. These effects were caused by the activation of
inhibitory neurons rather than decreased spiking of excitatory neurons, since
archaerhodopsin-3 (Arch)-mediated optical silencing of calcium/calmodulin-dependent
protein kinase II?-positive (CaMKII?+) excitatory neurons caused no significant change
in the cortical stimulus selectivity. Moreover, the sharpening of orientation tuning
specifically required inhibition from PV+ interneurons: although activating somatostatin
(SOM+) interneurons increased direction selectivity, it caused no sharpening of
orientation tuning, and activating vasointestinal peptide (VIP+) interneurons had no
effect on either response property. Notably, optical activation of PV+ interneurons in
awake mice caused a significant improvement in their orientation discrimination,
mirroring the sharpened V1 orientation tuning. Together, these results provide the first
demonstration that visual coding and perception can be improved by elevated spiking
of a specific subtype of cortical inhibitory interneurons.
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MGLUR2 AGONIST, DCG-IV, DECREASES SPIKE RATE OF MITRAL CELLS IN THE
ACCESSORY OLFACTORY BULB IN ANESTHETIZED MICE
Leszkowicz E (1,2) and Brennan PA (1)
(1) School of Physiology and Pharmacology, University of Bristol, Bristol, UK; (2)
Department of Animal Physiology, University of Gdansk, Gdansk, Poland
The mGluR2 receptor agonist, DCG-IV, has been hypothesised to promote memory
formation by disinhibiting mitral cell activity in the accessory olfactory bulb (AOB),
leading to increased feedback inhibition from granule cells. We tested a key aspect of
this hypothesis by recording DCG-IV effects on mitral cell activity in the AOB of
anaesthetised mice.
Animals received 1 ul infusion of CSF or 10, or 100 pmol of DCG-IV into the AOB. A
recording electrode was located in the mitral cell layer. Single unit activity in the mitral
cell layer was recorded before, during and after drug infusion.
DCG-IV not only did not disinhibit mitral cells but actually reduced their firing
frequency. The effect appeared during the infusion and was dose-dependent. The 10
pmol DCG-IV - induced decrease in spike rate was deeper and lasted longer than 100
pmol effect. Trends to return to the pre-infusion levels were observed in both groups.
Thus, this study failed to find a disinhibitory effect of DCG-IV on mitral cells that had
been predicted on the basis of in vitro data. These findings challenge the established
hypothesis that the memory inducing effects of DCG-IV are mediated by mitral cell
disinhibition.
MEMBRANE CHOLESTEROL MODULATES K+ CURRENTS AND SPONTANEOUS
ELECTRICAL ACTIVITY IN DEVELOPING HAIR CELLS
Snezana Levic and Ebenezer Yamoah
(1) Ecole Normale Superior, Paris and (2) University of California, Davis
Composition of lipids in cell membranes changes with development. Biophysical
evidence suggests that lipid microdomains may interact with ion-channel proteins to
regulate channel dynamics. In developing hair cells, membrane properties are very
different from adults. For example, only developing hair cells are capable of supporting
action potentials. Thus, there may be something unique about nature of protein lipid
interactions in developing vs adult hair cells.
In this study, we examined effects of cholesterol depletion on K+ currents and
electrical activity of hair cells at different stages of chicken embryonic development,
E6-E21, as well as post hatched chickens.
We will present data that demonstrates: 1) the presence of cholesterol sensitive
currents in developing hair cells 2) the role of cholesterol sensitive currents in
spontaneous electrical activity
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ALTERED SYNAPTIC PLASTICITY AND RHYTHMIC OSCILLATIONS IN THE
HIPPOCAMPUS FOLLOWING VASCULAR INJURY AND BLOOD BRAIN-BARRIER
DYSFUNCTION
Lippmann K (1), Nichtweiß J (1), Reichert A (1), Bar-Klein G (2), Heinemann U (2),
Friedman A (2)
(1) Institute of Neurophysiology, Charité University Medicine, Berlin, Germany; (2)
Department of Physiology, Faculty of Health Sciences, Ben-Gurion University of the
Negev, Beersheba, Israel
Recent studies have elucidated a key role for dysfunction of the blood-brain barrier
(BBB) in the pathogenesis of neuronal dysfunction, epileptogenesis and delayed
neurodegeneration within the neocortical network. Since the hippocampus - a brain
area involved in high cognitive functions - is sensitive to vascular insults we
investigated electrophysiological alterations in vivo and ex vivo following BBB injury
using the photosensitive agent Rose-bengal (RB). The sensorimotor cortex of rats was
exposed to 15 min halogen light following i.v. injection of RB. Using Evans blue
injections, we confirmed BBB dysfunction within the hippocampus from 12 h to 1 week
following treatment with no acute cell death. Intrahippocampal recordings were
obtained using a telemetric system (Data Science International) from 1 week prior to 1
week following RB treatment. Ex vivo electrophysiological recordings were obtained
from the CA1 region of the hippocampal slice using routine procedures. In-vivo
recordings confirmed increased high frequency activity within the BBB-injured
hippocampus. Ex-vivo recordings showed increased likelihood of spontaneous high
frequency paroxysmal activity, lower threshold for spreading depolarization and
reduced long-term potentiation upon tetanic stimulation. Our findings suggest
significant hippocampal dysfunction in the presence of peri-ischemic vascular injury
and new understandings of the sequence of events underlying cognitive dysfunction in
vascular pathologies.
DOPAMINE NEURONS SIGNAL REWARD FOR ODOUR MEMORY IN DROSOPHILA
Liu C, Friedrich AB, Siwanowicz I, Tanimoto H*
Max-Planck-Institute of Neurobiology, Germany
Dopamine (DA) plays important roles in variety of behaviors and is widely accepted as
the critical neurotransmitter for signaling the punishment in aversive associative
learning in Drosophila flies. Although recent studies revealed that DA also contributes
to appetitive learning in adult flies and larvae, cellular mechanisms for reward signaling
are unknown. Here, by transient activation and inactivation of target neurons in the fly
brain, we show that a specific group of DA neurons are required for the formation of
appetitive memory, and convey reward information to the medial lobes of the
mushroom bodies.
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RIM BINDING PROTEIN IS A CORE COMPONENT OF THE ACTIVE ZONE CYTOMATRIX
AND ESSENTIAL FOR NEUROTRANSMITTER RELEASE
Liu K (1)*, Siebert M (1)*, Mertel S (1)*, Knoche E (1)*, Wegener S (2)*,
Wichmann C (1), Matkovic T (1), Muhammad K (1), Depner H (1), Mettke C (1),
Bückers J (3), Hell SW (3), Müller M (4), Davis GW (4), Schmitz D (2), Sigrist SJ (1)
*contributed equally;
(1) Freie Universität Berlin, Germany; (2) Charité Universitätsmedizin Berlin, Germany;
(3) Max-Planck-Institut for Biophysical Chemistry, Germany; (4) University of
California, San Francisco, USA
Synaptic transmission is enabled by the fusion of synaptic vesicles (SVs) at presynaptic
active zone (AZ) membranes. The concerted action of the core fusion machinery
ensures SV fusion, while the AZ-associated protein scaffolds (cytomatrices) are
considered to play a modulatory role in this process. Here, we show that Drosophila
RIM binding protein (DRBP), a component of the AZ cytomatrix, is not only crucial for
the integrity of this protein scaffold, but also essential for evoked neurotransmitter
release. Using stimulated emission depletion and electron microscopy, we show that
DRBP tightly surrounds the central Ca2+ channel field at the base of the AZ
cytomatrix. This cytomatrix is defective in drbp mutants, and synaptic responses to
single action potentials are severely reduced. Specifically, Ca2+ channel clustering and
Ca2+ influx are impaired, and the synaptic release probability is decreased. This is
reflected by an impressive short-term facilitation in drbp mutants. Based on this data,
we propose that the highly conserved RBP proteins are prime effectors of the AZ
cytomatrix, where they link SVs, Ca2+ channels and the SV fusion machinery.
LHX7 IS REQUIRED IN MOUSE STRIATAL CHOLINERGIC INTERNEURONS TO
MAINTAIN NEURONAL SUBTYPE IDENTITY
Lopes R, Verhey van Wick N, Neves G and Pachnis V
Division of Molecular Neurobiology, MRC National Institute for Medical Research, UK
The cholinergic and GABAergic interneurons of the striatum derive from a pool of
embryonic progenitor cells that upon exiting the cell cycle express the LIM
homeodomain proteins Lhx6 and Lhx7. Previous reports have shown that the correct
specification of cholinergic interneurons from a subset of these post-mitotic precursors
requires expression of Lhx7, downregulation of Lhx6, and induction of another LIM-HD,
Isl1, whereas Lhx6 expression is required for terminal differentiation of the GABAergic
subset of interneurons. However, little is known about how the cholinergic identity is
maintained after the initial post-mitotic specification. To gain further insight into the
maintenance of cholinergic identity at later stages of development we used conditional
gene ablation to specifically delete Lhx7 in lineage-committed striatal cholinergic
interneurons. We demonstrate that Lhx7 is required to maintain cholinergic identity
and that upon ablation of this gene a large subset of these interneurons change fate to
acquire molecular and morphological characteristics of GABAergic interneurons.
Furthermore, we present evidence supporting a model where Lhx7 controls this
identity switch by gating a cross-regulation between Isl1 and Lhx6. We conclude that
the postmitotically acquired subtype identity is not irreversibly fixed as striatal
interneurons maintain remarkable phenotypic plasticity beyond commitment to a
lineage.
CHARACTERIZATION OF GLYCINERGIC TRANSMISSION IN AN IN VITRO EPILEPSY
MODEL
Luís C, Ribeiro JA, Sebastião AM and Valente CA
Institute of Pharmacology and Neurosciences, Faculty of Medicine, and Unit of
Neurosciences, Institute of Molecular Medicine, University of Lisbon, Portugal
Epilepsy is one of the most prevalent neurologic disorders worldwide. An imbalance
between neuronal inhibition and excitation is known to be involved in epileptogenesis.
Glycine, an inhibitory neurotransmitter, has been shown to have an antiepileptic effect
mediated by glycine receptors (GlyR) in the hippocampus.
This study aims to characterize the expression pattern of glycinergic transmission
markers associated with pharmacoresistant epileptiform activity onset in rat
hippocampus-enthorinal cortex (Hip-EC) combined slices.
Electrophysiological recordings showed that pharmacoresistant late recurrent
discharges (LRDs) developed after 2h-exposure to free Mg2+/ high K+ artificial
cerebrospinal fluid in the medial EC with a frequency of 14 ± 2 per min.
Subsequently Hip-EC slices were used for molecular-based approaches.
Western blot analysis of glycinergic transmission-related markers showed a slight
increase in gephyrin, a postsynaptic scaffolding protein essential in synaptic anchoring
of GlyR.
Quantitative real-time PCR revealed that GlyR alpha 2 and alpha 3 transcripts increase
in the epileptiform activity-induced conditions. This pattern has been reported in
temporal lobe epilepsy (TLE) patients.
These results suggest that this model mimics what occurs in TLE in vivo, making it a
useful experimental tool to investigate the molecular mechanisms underlying epileptic
disorders. Evidence further indicates that a compensation mechanism might occur
during epileptiform activity involving glycinergic transmission effectors.
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68
MORPHOLOGICAL ANALYSIS OF LAMINA I LOCAL-CIRCUIT NEURONS IN THE LUMBAR
SPINAL CORD OF THE RAT
Luz LL (1,4), Pinho R (1,4), Aguiar P (1), Antal Zs (2), Todd A (3), Safronov BV (1,4),
Szucs P (1)
(1) Instituto de Biologia Molecular e Celular, Portugal; (2) UD MHSC, Hungary; (3)
Univerity of Glasgow, UK; (4) Faculdade de Medicina da Universidade do Porto,
Portugal
Lamina I is known to integrate nociceptive information. Projection neurons, although
only ~5% of the neurons in this lamina, have been studied intensively while much less
attention has been given to local-circuit neurons (LCNs) that give the majority in
lamina I and are also crucial elements, presumably forming local and interlaminar
networks.
The infrared-LED oblique illumination technique allowed us to record, label and
reconstruct complete biocytin-filled LCNs, and to analyse their axonal and dendritic
branching patterns.
We have revealed a distinct neuronal population in lamina I, defined by an extensive
local axon and characteristic discharge patterns in response to depolarizing current
pulses. The initial myelinated part of their axon gives rise to several unmyelinated
small-diameter branches that have densely packed large varicosities and show
extensive distribution in all directions. Preliminary immunocytochemical results indicate
that the majority of these LCNs are inhibitory, while some of them express functional
neurokinin-1 receptors. The same time, initial branching order of the axon, varicosity
densities along the axonal tree and terminal field locations seem to show substantial
heterogeneity within the population.
Our observations indicate that these LCNs form intersegmental as well as interlaminar
connections, providing anatomical substrate for rostrocaudal "processing units" in the
dorsal horn.
ARBUTUS UNEDO PHYTOCHEMICALS PROTECTIVE EFFECTS ON THE YEAST
PARKINSON’S DISEASE MODEL
Diana Macedo (1), Sandra Tenreiro (2), Tiago F. Outeiro (2), Ricardo B. Ferreira
(1,3), Cláudia N. Santos (1,4)
(1) Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras,
Portugal; (2) Instituto de Medicina Molecular, Universidade de Lisboa, Lisboa, Portugal;
(3) Departamento de Botânica e Engenharia Biológica, Instituto Superior de
Agronomia, Universidade Técnica de Lisboa, Lisboa, Portugal; (4) Instituto de Biologia
Experimental e Tecnológica, Oeiras, Portugal.
Arbutus unedo (strawberry tree) extracts, protects cells from oxidative stress and ?Synuclein (aSyn) induced toxicity, on the yeast Parkinson’s disease (PD) model. aSyn
aggregation is associated with the formation of Lewy bodies and in the causative
pathogenesis of PD. Although aSyn amyloidogenesis remain elusive, oxidative stress
seems to triggers its oligomerization. Therefore, agents that either prevent the
production of reactive oxygen species directly and/or inhibit toxic aSyn aggregation
could represent potential drug leads for PD. Among antioxidants, polyphenols are
acknowledged for their health promoting and neuroprotective effects. In this study
polyphenol enriched fractions obtained from A. unedo, leaves and fruits, were analysed
for potential neuroprotective activities using the yeast PD model. A. unedo is a native
Mediterranean species with promising health beneficial characteristics, based on its
phenolic content and antioxidant capacity. Rubus idaeus and Ginkgo biloba, with well
documented health promoting activities, were used for comparison purposes. A. unedo
improved cell viability under H2O2 and aSyn induced toxicity conditions on yeast. The
cellular mechanisms underlying this protection may be related with the reduction of
aSyn aggregates, analysed by microscopy. Taken together, the results suggest A.
unedo phytochemicals as a potential neuroptotectors directed toward the prevention of
PD.
DIFFERENTIAL REGULATION OF SYNAPTIC VESICLE TRANSPORT IN VIVO IN
C.ELEGANS
Maeder CI, Wu YE, Klassen MP and Shen K
Stanford University, USA; UCSF, USA
Polarized distribution of synaptic components to axons and dendrites is crucial for
neuronal function. However little is known how polarized neuronal transport is
precisely mediated and regulated in vivo.
I utilize C.elegans to quantitatively investigate polarized trafficking of SVs in the DA9
motor neuron. Using time-lapse microscopy, I follow the movement of SV markers
such as rab-3 and synaptogyrin-1. I find that transport of these two markers is highly
correlated. Furthermore I show that SV trafficking is differentially regulated in axons
and dendrites. Detailed analysis of SV directionality reveals that SVs are transported
into the dendrite and move there equally in both directions. In the axon, however, SV
flow is always directed towards the en-passant synapses; hence the flow in the most
distal axonal compartment is in opposite direction as compared to more proximal
segments.
Characterizing different mutants I demonstrate that SV movement is strictly dependent
on UNC-104, the major axonal anterograde motor. Furthermore I find that a small arflike GTPase ARL-8 prevents premature assembly of SVs during transport thereby
preventing precocious synapse formation.
Taken together time-lapse microscopy proves as a powerful method to get mechanistic
insight into SV transport, a crucial step in neuronal cell polarity establishment.
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DYNAMICAL CAUSAL MODELLING OF BETA SYNCHRONY IN PARKINSONIAN
NETWORKS
André Marreiros (1,2) Rosalyn Moran (2), Hayriye Cagnan (1), Karl Friston (2), Peter
Brown (1)
(1) Department of Clinical Neurology, University of Oxford, UK; (2) Wellcome Trust
Centre for Neuroimaging, UCL, London, UK.
Parkinson's disease (PD) is associated with abnormally synchronized oscillations in the
beta (13-35 Hz) frequency band in the cortical-basal ganglia-thalamo-cortical loop.
Treatment-induced reduction in the amplitude of these oscillations correlates with
motor improvement. Conversely, the artificial induction of beta oscillations slows
movement in patients with PD and healthy subjects, and causes parkinsonian
behaviour in rodents. These observations suggest that high levels of beta activity may
be mechanistically related to parkinsonian motor impairments, or, at the very least,
provide a faithful marker of the parkinsonian state. Thus the network changes that
underpin this activity may be highly informative about the pathophysiology of the
disease and help direct the search for new treatment targets. The goal of this study is
to take local field potentials (LFPs) recorded during or following deep brain surgery in
PD patients and discern from these how different brain areas interact in the network.
We used data from PD patients who underwent implantation of deep brain stimulation
(DBS) electrodes in the globus pallidus interna (GPi) and STN. Thus, for a short spell,
we were able to record LFPs from GPi and STN and simultaneously record EEG from a
scalp electrode overlying mesial motor areas. Recordings were made both OFF and ON
the dopaminergic prodrug levodopa. We convolved the cortical-basal ganglia-thalamocortical model established previously in the rodent and applied a dynamic causal model
(DCM) of steady-state responses (SSR) to this data. We looked at the time-frequency
analysis of resting state data between recordings made OFF and ON levodopa.
Differences in effective connectivity underlying the spectral densities were studied for
ON and OFF levodopa. This study presents the first extension of a DCM rodent model
of the network changes supporting pathological beta activity in parkinsonism to a
patient with PD.
NORADRENERGIC GATING OF LONG-TERM CORTICAL SYNAPTIC PLASTICITY
Ana Raquel Oliveira Martins (1,2) and Robert C. Froemke (2)
(1) PhD Programme in Experimental Biology and Biomedicine (PDBEB), Center for
Neurosciences and Cell Biology, University of Coimbra, Portugal; (2) Skirball Institute of
Biomolecular Medicine, Department of Otolaryngology, Physiology and Neuroscience,
New York University School of Medicine, New York, NY, USA
Neuronal cortical networks are plastic, able to reorganize throughout life.
Neuromodulator release is required for cortical plasticity, but it is uncertain how
subcortical neuromodulatory systems, like the noradrenergic locus coeuruleus, interact
with cortical circuits. Here we study the dynamics of auditory cortical receptive field
plasticity at the synaptic level using in vivo whole-cell recording. Adult rats were
anesthetized, stimtrodes were implanted in the locus coeruleus, and a craniotomy
performed over the primary auditory cortex. After mapping the tonotopic field of the
primary auditory cortex, intracellular neuronal recordings were made (usually in layer
V), and pure tones of varying frequencies were presented to the animal to characterize
tonal receptive fields. Pairing pure tones with locus coeruleus activation (to release
noradrenalin) dramatically changed the tuning properties of cortical neurons. For most,
pairing largely increased tone-evoked responses. In some cases, these changes were
highly stimulus-specific, while in other cases, tuning was degraded across all
frequencies. Changes in tuning curve shape continued to evolve over time to
emphasize and disambiguate the paired stimulus from other unpaired stimuli. Multiple
recordings from the same animal for hrs after a single episode of pairing suggest that
these changes in AI tuning stabilized after 6hr and could persist for 11+ hr.
Furthermore, in some AI neurons initially unresponsive to tones, during and after locus
coeruleus pairing, tone-evoked responses emerged, persisting for the duration of postpairing recordings (30+ min). This suggests the involvement of the locus coeruleus in
integration of ‘silent neurons’ into a specific auditory memory trace or cortical
representation of potentially behaviorally important sensory stimuli. We hypothesize
that such changes to cortical tuning curves have important implications for the
detection and/or discrimination of different sensory inputs.
THE REWARD DURATION IN APPETITIVE CONDITIONING OF HARNESSED
HONEYBEES IS STORED IN A LONG-TERM MEMORY AND DETERMINES THE
MEMORY’S STABILITY
Marter K, Eisenhardt D
Freie Universität Berlin, Institut für Biologie, Neurobiologie, Berlin, Germany
The term associative strength (AS) describes the extent to which the conditioned stimulus
(CS) predicts the reward (unconditioned stimulus, US). It is generally accepted that the AS
is mirrored in the conditioned response (CR) during acquisition. Our recent work
demonstrates a correlation between the US duration during acquisition and the
susceptibility of an extinction memory for protein synthesis-inhibition in honeybees
(Stollhoff & Eisenhardt, 2009). However, the US duration had no effect on the CR during
acquisition. This might be due to the fact, that the occurrence of the CR was recorded
dichotomous. Here, we asked whether quantifying the CR by electromyograms of a muscle
responsible for proboscis extension, uncovers the effect of the reward duration on
acquisition. In addition, we asked whether the reward duration impacts retention of
different memories and whether it changes a LTM’s resistance to extinction. Although we
find no effects during acquisition and on mid-term memory, we demonstrate two impacts
of reward duration on LTM: (1) animals form a memory about the duration of the reward.
(2) Reward duration determines the stability of this LTM.
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NOVELTY SEEKING BEHAVIOR IN JUVENILE AND ADULT MICE
Gabriela J. Martins, Ana Vaz, Costa RM
Champalimaud Neuroscience Program at Instituto Gulbenkian de Ciência, Oeiras,
Portugal
In humans, adolescence is a developmental stage which involves increased reward and
novelty-seeking. However, the underlying mechanisms of this behavior are not yet well
understood. It is postulated that dopamine-mediated circuitry is involved with rewardseeking behavior and interestingly the binding sites of dopamine receptors and
transporter dramatically increase during adolescence. Previous studies in mice have
demonstrated that random ratio schedules of reinforcement favor the formation of
goal-directed behavior whereas interval schedules favor habit formation. Therefore, in
an attempt to address the development of reward and novelty-seeking behavior, mice
were trained on a random ratio schedule, as previously described, to press a lever for
'novelty', in which light flashes and tones were presented as reinforcement. Like
instrumental studies using food reinforcers, juvenile mice increased their responses as
they were trained on the ratio schedule but decreased lever pressing after the
contingency between pressing and ‘novelty’ was degraded and even specifically
unpaired. Furthermore, these juvenile mice also failed to generalize their lever pressing
to a novel lever, suggesting that their behavior had the same characteristics as the
goal-directed behavior of adult mice. Studies are currently looking at the role of
dopaminergic signaling in novelty-seeking by assessing juvenile mice lacking the
dopamine transporter.
A REPRESENTATION OF TIME IN THE STRIATUM OF BEHAVING RATS
Gustavo Mello, Sofia Soares, Joseph Paton
Champalimaud Neuroscience Programme, Portugal
Animals from insects to humans learn and use information about temporal structure in
the environment on a scale of seconds to minutes to guide their actions. Yet in
mammals, there has not been a direct demonstration of how the brain might encode
time on this scale. The basal ganglia (BG) are a site of convergence for information
from a broad set of functional territories, and appear to be necessary for the
behavioral expression of learned temporal information. We recorded neuronal activity
from a major BG input structure, the striatum, in rats trained to press a lever for liquid
reward under conditions of changing reward availability times. Lever pressing was
completely self-initiated and rats demonstrated knowledge of changing intervals of
reward availability through adjustments in lever pressing start times. Neural activity
during task performance showed varied dynamics around the temporal cue, in this
case reward. Reordering of neurons based on time of activation relative to reward
revealed a slow-propagating wave of activity across the population. If treated as a
proxy for a simultaneously recorded ensemble, this pattern of activity produces a nonrepeating trajectory in the state of the network that can then be used to read out time
over the range of tens of seconds to one minute. The accuracy of time estimates
derived from this pseudo-ensemble appear to change along with behavior at block
divisions where intervals changed, suggesting animals may use a similar representation
to guide their actions. These findings suggest that the dynamics of activity patterns in
BG circuits may underlie the striatum’s importance in interval timing.
APPLICATION OF DISENTANGLED GENERATORS OF HIPPOCAMPAL LFPS TO STUDY
NETWORK DYNAMICS
G. Martín-Vázquez (1), N. Benito (1), A. Fernández-Ruiz (1), A. Korovaichuk (1), J.
Makarova (1), V.A. Makarov (2), O. Herreras (1)
(1) Cajal Institute - CSIC, Madrid; (2) Fac. of Mathematics, Univ. Complutense, Madrid,
Spain.
The information exchange between brain nuclei is made by temporal series of spikes
sent by rapidly changing groups of neurons. Reading such extremely parsed flow of
information is a must to understand network function. Local field potentials (LFPs) are
raised by the ongoing synaptic activity generated by converging pathways in a brain
region, and its complex temporal structure reflects that of the varying groups of
activated presynaptic cells. Because of the spread of currents in the extracellular
space, it is hard to know whether LFPs are generated by one or several synaptic inputs
close in space. By using independent component analysis (ICA) of multisite linear
recordings in the hippocampus of the anaesthetized rat we recently separated the
original sources of LFPs whose spatial distribution matched the known distributions of
axons terminals from different pathways. In companion papers we show (a)
biophysical evidence for robustness of source separation and millisecond temporal
precision, and (b) the elementary composition of pathway-specific LFPs matching the
activity of presynaptic units. Here we show the application of ICA-separated LFP
sources to explore functional network dynamics in anaesthetized rats. Among others,
we show coherent or uncorrelated activity of the units that belong to an homogeneous
population, functional topology of connections between two populations, varying levels
of activity of one population upon interference to specific pathways, functional chains
of activity in multiple relés, and multiple presynaptic generators for characteristic LFP
frequencies.
PRESYNAPTIC MGLUR1BETA MEDIATES HOMEOSTATIC ADAPTATION IN A SPINAL
GABAERGIC INHIBITORY CIRCUIT
Mende M, Pierce JP, Fletcher E, Francesconi A, Milner TA, Mentis GZ, Kaltschmidt JA
(1) Sloan Kettering Institute, USA; (2) Weill Cornell Medical College, USA; (3) Columbia
University, USA; (4) Albert Einstein College of Medicine, USA
Coordinated function of neural circuits within the mammalian CNS relies on the proper
balance of excitation and inhibition. However, the cellular mechanisms underlying the
homeostatic regulation of this balance in vivo remain unresolved. In the spinal reflex
circuit, incoming axons from proprioceptive sensory neurons form excitatory
glutamatergic synapses with spinal motor neurons that innervate the same muscle in
the periphery. Built into this circuit are inhibitory GABAergic interneurons (GABApre)
that refine and control sensory-motor signaling by forming axo-axonic contacts on
sensory afferent terminals. To investigate the mechanisms underlying homeostatic
adaptation in this circuit, we examined the effect of disturbing excitatory sensory
signaling — through vesicular Glutamate transporter vGlut1 depletion — on the
development of GABApre terminals. We found that vGlut1 elimination from sensory
afferents leads to decreased expression of GABA producing enzymes GAD67 and
GAD65 in GABApre terminals, suggesting downregulation of GABApre inhibitory
function in response to perturbed excitatory sensory afferent signaling. We further
found that GABApre terminals express the metabotropic Glutamate Receptor1
(mGluR1) beta and that GABApre terminals in mGluR1 mutant mice have reduced
GAD67 expression levels. We propose a model whereby GABApre terminals detect
changes in sensory afferent terminal activity through mGluR1beta, leading to
compensatory adaptation of presynaptic inhibition.
73
74
ODOR DETECTION VS. ODOR CATEGORIZATION: LINKS BETWEEN SPEED-ACCURACY
TRADEOFF AND NOISE SOURCES
André G. Mendonça (1), Maria I. Vicente (1), Alex Pouget (2) and
Zachary F. Mainen (1)
(1) Champalimaud Neuroscience Programme at Instituto Gulbenkian de Ciência,
Oeiras, Portugal; (2) University of Geneva, Switzerland
Speed-accuracy tradeoffs (SATs) are well known in cognitive and perceptual decisionmaking, and can involve large (>50%) changes in processing time (e.g. for randomdot motion stimuli). However, in some tasks, such as odor mixture categorization,
much smaller SATs (order 10%) are observed. Why some tasks benefit more from
temporal processing than others is not well understood.
To tackle this problem we compared SAT in the odor mixture categorization task to
that in a new odor detection task. We found that SAT (difference in RT from the
easiest to the hardest problem) was larger in odor detection than in mixture
categorization (40% vs. 12% increase in RT). These results suggest that accuracy is
also influenced by non-sensory variability that is not subject to integration. We have
explored this hypothesis by developing a computational model that incorporates two
sources of noise: fast, within-trial noise; and slow, trial-to-trial noise. We find that the
first plays a significant role in odor detectability, while the second is critical for
categorization. In sum, we demonstrate a clear separation, exposed in problem-specific
SATs, between signal detection and decision criterion that the brain has to cope with.
VOLTAGE SENSITIVE DYE IMAGING IN MOUSE REVEALS THAT CORTICAL MOTIFS IN
SPONTANEOUS DEPOLARIZATIONS REFLECT UNDERLYING FUNCTIONAL CIRCUITS
USED DURING SENSATION
Mohajerani MH., McVea D., Reimers M. and Murphy TH.
Brain Research Center, University of British Columbia, Vancouver, Canada
Spontaneous neuronal activity is not noise, but reflects the orchestrated action of
underlying brain circuitry. Using fast voltage sensitive dye (VSD) imaging, we
compared the spatiotemporal structure of ongoing spontaneous and stimulus-evoked
activity in the primary, secondary and association (retrosplenial, cingulate) cortices of
anaesthetized adult C57bl6 mice (n=14). Correlation analysis between sensory-evoked
(including visual, somatosensory and auditory) VSD signals and spontaneous activity
reveal that spontaneous activity can be decomposed into repeating motifs that are also
present during sensation. Moreover, we find that visual, somatosensory,and auditory
sensory-evoked responses activate a common area of motor, cingulate and
retrosplenial cortices (activated 27 ± 5 ms following stimulus onset; n=12). These
midline areas were also the most active spontaneously in the absence of sensory input
(17% higher that somatosensory and visual cortices in average n=10; pdlimb and
visual cortical regions. We interpret these results as evidence that spontaneous cortical
activity reflects underlying structural and functional circuitry of the cortex, and that it's
regional cross-modal spatiotemporal structure is strongly influenced by recent
experience. It is conceivable persistent spontaneous activity could be a mechanism for
information storage and coordination of activity across different cortical areas.
75
REPRESENTATION OF TIMING OF ACTIONS IN THE RAT PREMOTOR CORTEX
Murakami M, Vicente MI, Costa GM, Mainen ZF
Champalimaud Neuroscience Programme, Portugal
Acting at the right moment is important for adaptive behavior, but the mechanisms
governing the exact timing of actions controlled by the cortex are not well understood.
To understand how the nervous system determines the action timing which is freely
chosen by subjects, we studied representation of timing of actions at a single neuron
level in the rat secondary motor cortex (M2).
We trained rats to trigger a specific action at highly variable times by using a waiting
paradigm. Through multiple single neuron recordings from the rat M2, we found
neurons with a gradual increase in the activity during waiting. The rate of the increase
was negatively correlated with time to the action and the activity reached a constant
firing rate threshold just before the action. We also found a different class of neurons
which could represent timing of actions. These neurons showed transient correlation
between firing rate and action timing. The typical example was a neuron with a
transient burst in firing upon the start of waiting.
These results revealed a potential representation of the timing of actions in the rat
premotor area and thus help to constrain a circuit model for generation of self-timed
actions.
NEURONAL MECHANISMS UNDERLYING SEX HORMONE-DEPENDENT SWITCHING OF
SEXUAL RECEPTIVITY IN FEMALE MICE
Nomoto K and Lima SQ
Champalimaud Neuroscience Program, Lisbon, Portugal
Sexual behavior is a fundamental process for the survival and maintenance of the
majority of animal species. Female copulatory behavior is heavily influenced by sex
hormones, showing a peak in sexual receptivity during the fertile period, whereas they
generally do not copulate during the rest of the cycle. The hypothalamus, particularly
the ventromedial nucleus (VMH), is a key player in the control of sexual receptivity,
mediating the interplay between external (e.g., environmental) and internal
(e.g., hormonal) cues to produce adaptive behavioral changes. The main goal of this
study is to understand how the orchestrated activity of VMH neurons produces
different behavioral outputs (specifically, from sexually non-receptive to receptive)
across the reproductive cycle. In particular, by using electrophysiology in freely
behaving female mice, we will examine our hypothesis that changes in male-evoked
neural responses are correlated to adaptive changes of female sexual receptivity.
Preliminary results show that we can record the neural activity of the VMH, an area not
very easily accessible, and that we observe stimulus locked activity. Additionally, in
order to parse the contribution of specific cell types within the VMH for the regulation
of sexual receptivity, the use of optogenetic tools will be discussed.
76
A ROLE FOR MECP2 IN EXPERIENCE-DEPENDENT SYNAPTIC PLASTICITY
Noutel J (1,2), Hong YK (2), Leu BH (2), Kang E (2) and Chen C (2)
(1) Doctorate Program in Biomedicine and Experimental Biology, Center for
Neuroscience and Cell Biology University of Coimbra, Coimbra, Portugal; (2)
Department of Neurology, F.M. Kirby Neurobiology Center, Children’s Hospital Boston,
Harvard Medical
Mecp2 mutations underlie the neurodevelopmental disorder Rett (RTT) syndrome. One
hallmark of RTT is relatively normal development followed by later onset of symptoms.
Studies indicate an etiology of disrupted synaptic function, yet it is unclear how these
abnormalities explain the clinical presentation of RTT.
Objective: we investigated synapse development in Mecp2-deficient mice at a circuit
with distinct developmental phases: the retinogeniculate synapse.
Results: Electrophysiology data shows that retinogeniculate refinement is comparable
to that of wildtype littermates between postnatal days 9-21, indicating that initial
phases of synapse formation, elimination and strengthening are not significantly
affected in Mecp2 mice. However, during the later experience-dependent phase of
synapse remodeling (P27-34), the circuit becomes abnormal as relay neurons are
innervated by a higher number of weaker inputs. A reduction in the number of release
sites must account for the majority of the decrease in synaptic strength, since release
probability is not altered and quantal size only modestly reduced. Consistent with a
later phenotype, abnormalities in eye-specific segregation are observed at P46-51 but
not at P27-34. Finally, synaptic plasticity in response to visual deprivation is disrupted
in mutants.
Conclusion: These results suggest a crucial role for Mecp2 in experience-dependent
refinement of synaptic circuits.
SOCIAL STRESS IN ZEBRAFISH: THE ROLE OF COGNITIVE APPRAISAL ON SOCIALLY
DRIVEN CHANGES IN BRAIN TRANSCRIPTOME
Rui F. Oliveira (1,2), José M. Simões (1,2), Ana C. Oliveira (1,2)
(1) ISPA-Instituto Universitário, Lisboa, Portugal; (2) Champalimaud Neuroscience
Program, Instituto Gulbenkian de Ciência, Oeiras, Portugal
Introduction: Unlike physical stressors that can be conveyed directly by sensory
experiences, social stressors do not represent physical features of the world and
therefore have to be evaluated by some kind of appraisal mechanism. Thus, the
response to a social stressor is expected to involve a cognitive evaluation of the stimuli
that assesses its valence and salience to that organism at that moment in time. In this
study we investigated the role of cognitive appraisal on the activation of a genomic
response to a social stressor (staged agonistic interaction) in zebrafish.
Methods: After a period of social isolation male zebrafish were allocated to one of three
treatments that lasted for 30 min: (a) fight with a real opponent; (b) fight with its own
mirror image; (c) remain in social isolation (control group). In real opponent fight
winner and loser individuals were established by behavioural analysis. It is predicted
that if no cognitive appraisal is involved in the activation of a brain response to social
stress, both real opponent fighters and mirror fighters that engage in aggressive
behavior should express it. In contrast, if appraisal of the outcome of the fight is
needed, then a response is only expected in real opponent fighters since mirror
fighters do not experience winning or losing despite expressing aggressive behavior.
The neurogenomic response was measured for whole-brain samples using a
commercially available (Affymetrix) zebrafish genome microarray.
Results & Discussion: Cluster analysis of changes in gene expression at the
transcriptome level group correctly all the individuals according t their social experience
(i.e. winners, loser, mirror fighters and controls). An analysis of differentially expressed
genes using the control group as reference with a FDR of 10% identified a set of genes
differentially expressed in males fighting a real opponent (23 in winners, 133 in losers
and genes, 64 shared by winners and losers) but none were detected in mirror
fighters. Microarray analysis was confirmed for a sub-set of differentially expressed
genes using qRT-PCR. These results suggest that it is not the objective structure of the
event that triggers a genomic response to a social stressor but rather the appraisal that
the individual has of the putative stressor. For males fighting a real intruder losing had
a higher impact on changes in gene expression than winning suggesting that it has a
higher salience to the subject, and a stronger impact in biological processes.
Research Support: Funded by Fundação para a Ciência e a Tecnologia (FCT, Portugal)
research grant # PTDC/PSI/71811/2006
77
78
EXCITOTOXICITY IN CEREBELLAR GRANULE CELLS TRANSDUCED WITH MUTANT
ATAXIN-3
Oliveira-Sousa SI (1), Laço ML (1), Nobrega C (1), de Almeida LP (1,2) and
Rego AC (1,3)
(1) Center for Neuroscience and Cell Biology; (2) Faculty of Pharmacy; and (3) Faculty
of Medicine, University of Coimbra, Portugal
Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3, is one of
nine polyglutamine disorders caused by the expansion of CAG trinucleotide repeats
within the coding region of MJD1 gene, which codifies for ataxin-3 (ATX3). MJD
pathological symptoms become apparent when the CAG expansion is longer than 52
repeats. The polyglutamine tract, located at the C-terminus of expand ATX3, induces
conformational changes in protein, leading to misfolding and accumulation in
ubiquitinated nuclear inclusions. Despite widespread expression of expanded ATX3
protein, neurodegeneration occurs in specific brain regions, such as the dentate
nucleus of the cerebellum, spinocerebellar tracts and particular nuclei of the brainstem
Our study indicates that selective stimulation of N-methyl-D-aspartate (NMDA)
receptors is cytotoxic to wild-type cerebellar granule cells with 14 days in culture and
decreases mitochondrial membrane potential upon influx of calcium, as evaluated by in
situ single cell analysis. Currently, we are evaluating the susceptibility of mice
cerebellar granule cells transduced with lentiviral vectors encoding for expanded versus
wild-type human ATX3 to NMDA excitotoxicity, in order to clarify the role of excessive
glutamate neurotransmission in MJD pathogenesis.
ROLE OF GRANULE CELLS FOR ODOR IDENTIFICATION IN COMPLEX OLFACTORY
SCENES
Otazu GH and Albeanu DF
Cold Spring Harbor Laboratory, USA
The identification of odor sources is essential for survival. However, odors are not
presented in isolation, as natural scenes consist of a superposition of signals
originating from multiple sources. This identification is a complex computational
problem that is readily solved by most animals. We present a model of the corticobulbar circuit, called the Corrected Projections Algorithm or CPA, that performs levelinvariant recognition of olfactory objects in complex olfactory scenes. CPA identifies the
objects present from a large dictionary of possible elements and operates reliably with
multiple sources present. The key assumption is that the activity of cortical neurons
encode the difference between the olfactory signal and an estimate. This error signal is
sent to the olfactory bulb, where it is used to refine an estimate about which odors are
actually present. CPA indicates that the activity of granule cells, the main recipients of
cortical feedback, would show an intensity and fluctuation invariant representation of
the odors present. We also propose a specific computational role for the reciprocal
connection between granule cells and mitral cells. We are developing a combination of
electrophysiological, optogenetic, and behavioral experiments to test the role of
granule cells in the analysis of complex olfactory scenes.
79
HEMISPHERIC SPECIALIZATION OF AUDITORY CORTICAL CIRCUITRY
Oviedo HV, Zador AM
Cold Spring Harbor Laboratory, USA
The lateralization of some functions performed by the cortical hemispheres has evolved
to increase processing efficiency and decrease interference. Human studies have
revealed anatomical differences between corresponding areas of the two hemispheres,
but how these differences are related to functional asymmetry is not known. Recent
behavioral studies have shown that similar to humans, rodents display evidence of a
“right/left-ear advantage” in auditory processing, and lesions to the auditory cortex
have been directly linked to a deficit in these functions. Therefore, we examined
whether there is evidence for hemispheric specialization of auditory cortical circuits in
the mouse. To probe for functional circuit differences between the two hemispheres,
we used Laser Scanning Photostimulation (LSPS) combined with voltage-clamp
recordings of layer 3 pyramidal cells. A previous study (Oviedo HV et al., Nature
Neuroscience, 2010) showed that layer 3 cells in the left auditory cortex receive
asymmetrical (out-of-column) projections from layers 5/6. We examined whether these
projections are translationally invariant across the tonotopic axis of auditory cortex in
the left and right hemispheres. We found that projections to layer 3 are not
translationally invariant: mapping across the tonotopic axis gives rise to different
spatial input patterns. Further, these patterns suggest circuit mechanisms that could
give rise to the “right/left-ear advantage” of linguistic and non-linguistic processing.
GENETIC ANALYSIS OF EPHA4 IN SPINAL AND SUPRASPINAL CIRCUITS
CONTROLLING LOCOMOTION
Paixão S (1), Balijepalli A (1), Memic F (2), Zheng B (3), Kullander K (2), Klein R (1)
(1) Max-Planck Institute of Neurobiology, Martinsried, Germany; (2) Department of
Neuroscience, Uppsala University, Sweden; (3) Department of Neurosciences,
University of California San Diego, La Jolla, CA, USA
EphA4 KO mice walk with synchronous movements of the hindlimbs producing a
hopping gait. EphrinB3, expressed at the midline of the spinal cord (SC), is a ligand
and repellent of the EphA4 receptor. Removal of the receptor or the ligand results in
aberrant midline recrossing of corticospinal axons (CST), shallowing of the dorsal
funiculus (DF), where longitudinal CST axon bundles are located, and aberrant midline
crosses of central pattern generator (CPG) neurons.
Using an EphA4 conditional allele we have dissected the function of EphA4 in the
establishment and function of the spinal and cortical circuits controlling locomotion.
Removal of EphA4 from the forebrain (using Emx1-Cre) leads to a misguidance of CST
axons without altering the DF morphology. The bilateral CST innervation observed
does not seem to affect gait or adaptive locomotion in these mice.
Removing EphA4 in the dorsal neuron population (using Pax7-Cre) phenocopies EphA4
KO mice, with a shallow DF, ectopic EphA4-positive cells at the midline, and
surprisingly aberrant recrossing of CST axons. These mice also show an uncoordinated
gait, alternating between normal asynchronous steps and hops. We think that the SC
morphological phenotypes could be due to a midline defect in the region originally
occupied by the DF.
80
LESSONS FROM OTHERS: A STUDY OF THE MECHANISMS UNDERLYING SOCIAL
TRANSMISSION OF FEAR
Ana Pereira, Andreia Cruz and Marta Moita
Champalimaud Centre for the Unknown, Lisbon, Portugal
Communication of danger between con-specifics is present across different species.
Despite being a widespread phenomenon little is known about the mechanisms
underlying social transmission of fear- STF. Using the Norway rat as a model, we
developed a behavioral paradigm to study STF, where a demonstrator displays fear
responses, in the presence of an observer cage-mate. We found that observer rats
freeze while witnessing a demonstrator displaying fear responses, provided they had a
prior fear learning experience with foot shocks. Also we found that the cessation of
sound of motion, as the demonstrator freezes, is a strong cue that is both sufficient
and necessary for STF in rats. To separate the effect of simply receiving a foot shock
and learning that something is associated with it, we used an Immediate Shock Deficit
– ISD paradigm, where the animal is shocked immediately upon being placed in an
unfamiliar context. We found that animals that undergo ISD do not display vicarious
fear, suggesting that prior experience results in an associative learning event that
facilitates social transmission of fear.
IMPACT OF PHOSPHORYLATION ON THE MODULATION OF PRRXL1 ACTIVITY
Pessoa AS (1,2), Soares dos Reis R (1,2), Falcão M (1,2), Matos M (1,2), Monteiro CB,
Monteiro FA (1,2), Reguenga C (1,2), Lima D (1,2)
(1) Departamento de Biologia Experimental, Faculdade de Medicina, Universidade do
Porto, Portugal; (2) IBMC – Instituto de Biologia Molecular e Celular, Universidade do
Porto, Portugal
The establishment of synaptic connections between the PNS and CNS is a wellresearched subject, and many molecules have been identified as guidance factors for
the correct synapse. Prrxl1 is a homeodomain transcription factor essential for the
connectivity and survival of nociceptive neurons in the mouse embryo dorsal root
ganglion (DRG) and spinal cord (SC). How Prrxl1 exerts its function remains to be
ascertained.
Here we show, through dephosphorylation assays, Ga3+-Immobilized metal ion affinity
chromatography and 2D-electrophoresis, that Prrxl1 is highly phosphorylated. Most
importantly, Prrxl1 displays distinct phosphorylation patterns in the DRG and SC along
development. By Prrxl1 truncation analysis and CNBr chemical cleavages, we
demonstrate that phosphorylation occurs throughout the protein, clustering in the Nterminus (encompassing the DNA-binding domain) and in the C-terminus (containing a
conserved putative regulatory domain). Mutation of evolutionary conserved sites has
thus far revealed a phosphorylation site in the homedomain, whose mutation impairs
transcriptional activation and DNA-binding. Luciferase reporter assays of truncated
versions of Prrxl1 have identified the N-terminus as sufficient for the transcriptional
activity of Prrxl1.
Altogether, our results show that Prrxl1 is phosphorylated at multiple sites. Moreover,
these phosphorylations probably play a fundamental role in the regulation of Prrxl1
transcriptional activity in nociceptive neurons.
81
BALANCED EXCITATION AND INHIBITION DURING FUNCTIONAL MOTOR ACTIVITY IN
THE SPINAL CORD
Petersen PC and Berg RW
Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark
Central pattern generators (CPG) are neuronal ensembles underlying stereotyped
movements such as walking, swimming, and scratching. Often these movements can
be initiated and sustained without cortical input indicating that CPG’s reside locally in
the spinal cord where they constitute the neuronal basis for programmed motor tasks.
CPGs are conventionally described by the reciprocal model which consists of two
populations of neurons that have no rhythmic ability individually, but produce rhythmic
outputs when reciprocally coupled. In the model, motor neurons (MN) receive
excitation in phase and inhibition out of phase with muscle activity (Lundberg 1981).
However, experiments that directly measure the synaptic input to MNs in adult
vertebrates were unable to confirm the reciprocal arrangement (Berg et al. 2007). It
was hypothetized that this disparity was due to the experimental circumstances, that
the cord was transected at a lumbar segment (Grillner, Jessell 2009).
In order to resolve this claim, we conduct the experiment in a non-transected turtle
spinal cord preparation and estimate the inhibitory and excitatory synaptic conductance
in MN during scratching. With intracellular recordings from motor neurons we have
reaffirmed that there is a strong increase in conductance during motor activity and a
concurrent balanced increase in excitation and inhibition.
IMAGING THE ACTIVITY OF PROJECTIONS FROM THE MOTOR CORTEX TO THE
BARREL CORTEX IN MICE PERFORMING AN OBJECT LOCALIZATION TASK
Leopoldo Petreanu*, Diego Gutnitsky, Daniel Huber, Dan O’ Connor, LinTian, Loren
Looger and Karel Svoboda
Janelia Farm Research Campus, Ashburn VA USA.
*Now at Champalimaud Neuroscience Programme, Lisbon, Portugal
Vibrissae somatosensation is an active process. Animals have to integrate self-generated
movements of their vibrissae with the sensory responses evoked when objects are
contacted. This process is thought to depend on the interaction between the vibrissae
motor cortex (vM1) and the barrel cortex (vS1). Both cortical areas are heavily
interconnected by a large number of cortico-cortical fibers. vM1 projections densely
innervate layer 1 of vS1, where they contact the apical tuft of pyramidal neurons. The
precise signals relayed by these connections during active somatosensation remain
unknown. Here we used 2-photon Ca2+ imaging in axonal boutons to specifically measure
the activity of vM1 neurons projecting to vS1 in behaving mice. We transfected vM1
neurons with an adeno-associated virus encoding for the genetically encoded Ca2+
indicator GCaMP3 and imaged axonal boutons in layer 1 of identified barrels in vS1 as mice
performed a vibrissae-dependent Go/NoGo object localization task. The activity of vM1
axons in vS1 was highly heterogeneous, neighboring synapses within a barrel showing
activity that correlated with different aspects of the behavioral task. Across animals,
activity in a subset of synaptic terminals correlated with the movement of whiskers during
object localization but not during other epochs of the task. Thus, as predicted by many
sensorymotor integration models, an efferent copy of motor commands might be relayed
from motor cortex to somatosensory cortex during active whisking. Interestingly, the
activity of some vM1 terminals in vS1 correlated with contact forces of a single whisker,
not always corresponding to the principal whisker of the imaged barrel. This suggests that
during the object localization task both motor and sensory related signals might be sent
from vM1 to the apical tuft of vS1 pyramidal neurons.
82
INVESTMENT IN SEARCH: MEASURING CONFIDENCE IN ANIMALS
Pfuhl G (1,2), Biegler R (2)
(1) LU, Sweden; (2) NTNU, Norway
We developed a task to measure nonverbally the awareness of the precision of
knowledge (metamemory) in animals. To investigate this we used a delayed-matchingto-sample task where the number of pecks required for reward was variable. We
manipulated the confidence of the birds’ memory by using similar (‘hard’) or dissimilar
(‘easy’) pictures in the choice phase. Further, artificial pilfering or the absence of
reward even in correct choices was included. We tested it on two jackdaws (corvus
monedula) familiar with delayed matching to sample trials. Metamemory is seen as
more pecks in the ‘easy’ condition compared to the ‘hard’ condition in pilfered trials.
This expresses more confidence. We found that one jackdaw behaved in this manner.
In addition we omitted the sample stimulus, making the confidence judgment
independent from the choice phase. Metamemory is seen as refusing to search or
alternatively searching equally among all options. We found that both jackdaws did
more often refuse searching when given no sample phase then when a sample phase
was given. Further when they started to search in no sample phase trials both birds
invested equally in the ‘easy’ and ‘Hard’ condition. Thus the method is suitable for
assessing awareness and metacognition on-line/on the go in nonverbal subjects.
DISRUPTION IN CORTICAL INHIBITION LEADS TO ABNORMAL NETWORK DYNAMICS
IN THE PERINATAL KETAMINE MODEL OF SCHIZOPHRENIA
Pinto-Duarte A (1,2), Wang X (1), Jadi M (1), Behrens MM (1), Sejnowski TJ (1)
(1) Computational Neurobiology Laboratory, Salk Institute for Biological Studies and
Howard Hughes Medical Institute, USA; (2) Institute of Molecular Medicine and Faculty
of Medicine, University of Lisbon, Portugal
Schizophrenia is a mental illness with complex etiologies. Nevertheless, common
denominators, such as impaired cortical perisomatic inhibition, have been identified in
multiple animal models of the disorder.
To explore the mechanisms by which the reduction in cortical inhibition leads to
pathological brain states, we used the perinatal ketamine mouse model, known to
incur permanent loss of phenotype in parvalbumin (PV)-positive inhibitory neurons. We
combined immunohistochemistry, in vitro patch-clamp, electroencephalographic
recordings and computational modeling to elucidate the link between altered cellular
function and network behavior.
We found that perinatal ketamine treatment increased the variability of biophysical
properties of prelimbic PV-positive cells and reduced the excitatory drive they received.
It also downregulated the expression of GAD67 in PV-positive cells and attenuated
inhibitory inputs to pyramidal neurons. These changes were accompanied by a shift of
power from gamma to beta frequency range in frontal auditory evoked potentials
recorded in vivo. Using an excitation-inhibition model of cortical oscillations we
demonstrated that the alterations observed in vivo are a direct network-level
manifestation of synaptic changes characterized in vitro. By means of interdisciplinary
approaches, our work contributes to bridging the gap between the understanding of
cellular and systems-level mechanisms in rodent models of schizophrenia.
83
BEHAVIORAL CHARACTERIZATION AND NEURAL CONTROL OF SWIMMING SPEED IN
THE LARVAL ZEBRAFISH
Ruben Portugues, Kristen E. Severi, Florian Engert
Molecular and Cellular Biology, Harvard University, Cambridge, USA
Whole-field visual motion is known to elicit swimming in larval zebrafish (Neuhauss et
al 1999, Orger et al 2000). This reflex is termed the optomotor response (OMR). Our
interest is in understanding how larval zebrafish modulate a given motor program like
forward slow swimming to achieve different speeds of locomotion. We first characterize
freely swimming and head restrained behavior of larval zebrafish when presented with
whole-field motion, in the form of gratings, moving forward at different speeds. We
measure bout duration, bout length, interbout duration, latency and tail beat
frequency, all of which are shown to vary with grating speed. We then use in vivo
calcium imaging and electrophysiology techniques to investigate how this behavioral
modulation may be implemented at the neuronal level from a descending motor
control perspective. We focused on studying activity where responses to OMR stimuli
have been previously identified (Orger et al 2008), such as in the reticulospinal system
and in particular the nucleus of the medial longitudinal fasciculus. We characterize
specific activity patterns which correlate well with visual OMR stimuli of different
speeds in the range of interest identified in the behavioral experiments. These
descending motor control neurons may be contributing to modulation of spinal circuits
previously identified as being selectively activated at different swimming speeds
(McLean et al., 2008).
STRUCTURAL AND SYNAPTIC PLASTICITY DURING THE MGLURS- LTD
Ramiro-Cortés Y and Israely I
Neuronal Structure and Function Lab., Champalimaud Neuroscience Program, Lisboa,
Portugal.
Changes in synaptic weight are thought to be the physiological basis for learning and
memory. These changes can result in either potentiated or depressed synaptic
transmission (e.g. LTP or LTD) at individual synapses, and may physically alter
neuronal connectivity. Indeed, when individual synapses are potentiated through the
uncaging of glutamate and then monitored by live two-photon imaging, a linear
correlation between the increase in synaptic efficacy and the increase in spine volume
of that input is observed. Both the long lasting changes in plasticity and in structure
require new protein synthesis. However, it is unclear whether synaptically depressing
stimuli have structural correlates, such as the shrinkage or retraction of spines, or
whether spine shrinkage occurs independently of LTD. In order to investigate this
issue, we will induce LTD mediated by metabotropic glutamate receptors (mGluRs),
which is dependent on protein synthesis, in two ways: 1) globally, using the group 1
mGluR agonist DHPG and 2) at single spines, by glutamate uncaging. We will visualize
single spines with two-photon microscopy and record electrophysiological responses to
follow plasticity. The aim of this project is determine what are the structural correlates
of protein synthesis dependent LTD at dendritic spines.
84
THE ROLE OF DIFFERENT NOTCH LIGANDS IN THE CONTROL OF SPINAL CORD
NEUROGENESIS
Ramos C, Gaspar, C, Rocha S, Ferreira S and Henrique D.
Unidade Biologia do Desenvolvimento, Instituto Medicina Molecular- Faculdade de
Medicina de Lisboa, Portugal
The Notch pathway is an evolutionary conserved cell signaling system that regulates
cell fate decisions in many developmental processes, such as neurogenesis and
neuronal specification. In Drosophila, Notch is involved not only in the epidermal
versus neural decision, but also in specifying neuronal identity in several neuroblast
lineages. In vertebrates, Notch signaling has been shown to be required for progenitor
maintenance throughout the neurogenesis period, but a direct role in controlling
neuronal identity seems rather limited. My previous work focused on the role of
different Notch ligands during neurogenesis in the developing spinal cord (SC), and
contributed to show that the two main ligands, Dll1 and Jag1, are not directly involved
in specifying neuronal identity (Ramos, C. et al, 2010). Detailed analysis of conditional
KO mice lacking Dll1 and/or Jag1 revealed that, although these ligands are required to
maintain a pool of progenitors in the domains where they are expressed, the
acquisition of specific neuronal identities in these domains is independent of the type
of ligand that is active. This supports the view that neuronal type specification in the
SC is mainly controlled by the dorsal-ventral patterning system, with different neuronal
subtypes arising along a precise temporal order within each domain, determined by the
combinatorial network of transcription factors (TFs). The situation is different in the
pV2 domain, where various subtypes of V2 interneurons (INs) are generated from
apparently identical progenitors (Peng, CY. et al. 2007). A different regulatory network
must therefore control neuronal identity in this domain and my present work is
directed towards the understanding of this network. My results support a model where
the sequential activity of two Notch ligands, Dll1 and Dll4, coordinate consecutive steps
of V2 neurogenesis, controlling the rate of neuronal differentiation and creating
diversity in the population of V2 INs. I am using the V2 network as a model to
elucidate how extrinsic cues (Notch) and intrinsic factors (bHLH TFs) interact to
determine the acquisition of unique differentiation programs. My long-term aim is to
reach a deeper comprehension of the molecular logic underlying neuronal cell fate
specification in the developing vertebrate nervous system, which shall provide crucial
insight on how neural circuitries are assembled and function in the Central Nervous
System.
THE ROLE OF L LATERAL PFC IN PROCESSING OF SUPERORDINATE CONCEPTS
Raposo A, Mendes M, Marques JF
University of Lisbon, Portugal
Research on the processing of concepts at different hierarchical levels has suggested
that understanding superordinate concepts (e.g. fruit), relative to basic level concepts
(e.g. apple), requires greater semantic control that helps the retrieval of information in
a goal directed manner. Yet, it remains unclear what factors modulate the differential
executive demands associated with superordinate and basic level knowledge. We
tested the hypothesis that superordinate concepts have less shared features among
their members and therefore involve higher semantic control requirements. In an fMRI
study using a sentence verification task, we manipulated concept level (superordinate,
basic) and feature sharedness (more shared, less shared). Sentences involving less
shared features, relative to more shared features, significantly engaged the L lateral
PFC. More importantly, sentences that included superordinate concepts, relative to
basic level concepts, also revealed a strong response in L lateral PFC, along with
posterior temporal gyrus activation. There was also a significant interaction between
feature sharedness and concept level in L PFC and L posterior temporal areas. The
results suggest that understanding superordinate concepts requires extra semantic
control in L lateral PFC to coordinate information that is relatively low shared by the
members of the category.
85
86
EVIDENCE INTEGRATION ACROSS TIME AND SENSORY MODALITIES
David Raposo and Anne Churchland
Cold Spring Harbor Laboratory, Champalimaud Neuroscience Programme
A large body of evidence has examined the neural mechanisms that drive integration of
sensory evidence over time for decisions. However, real life situations frequently
necessitate integrating evidence not only across time, but across sensory modalities as
well- using auditory and visual inputs to parse speech, for example. Our goal is to
understand whether the same mechanisms that drive evidence integration over time
are relevant for evidence integration across modalities. As a first step towards this
goal, we developed a task that invites subjects (humans and rodents) to integrate
evidence both across time and across auditory and visual modalities: we presented
subjects with multi-modal event streams, consisting of a series of noise-masked tones
and/or flashes of light. Subjects made judgments about whether the event rate was
high or low. We confirmed that subjects’ decisions reflected evidence presented at all
times during the trial, consistent with integration of evidence over time. Further, for
both species, performance improved when stimuli were presented in both modalities
(cue-combination condition) compared to when stimuli were presented in a single
modality, consistent with evidence integration across modalities. Combining across
modalities could improve performance in two ways: by improving the detectibility of
congruent auditory and visual events, or, more abstractly by combining rate estimates
that are separately generated within each modality. Importantly, the improvement we
observed was evident both when the auditory and visual event streams were played
synchronously and asynchronously. The enhancement of rate estimates we observed
for asynchronous streams could not have resulted from improved detection of
individual events, which argues strongly that the subjects integrated overall rates that
were computed separately for auditory and visual inputs.
TLX3 AND PRRXL1 INTERACTION IS REQUIRED FOR PRRXL1 PROMOTER ACTIVITY
Regadas I (1,2), Soares dos Reis R (1,2), Matos M (1,2), Monteiro F (1,2), Lima D
(1,2) and Reguenga C (1,2)
(1) Departamento de Biologia Experimental, Faculdade de Medicina, Universidade do
Porto, Portugal; (2) IBMC – Instituto de Biologia Molecular e Celular, Universidade do
Porto, Portugal
Little is known about the molecular mechanisms that control the expression of the
homeobox gene Prrxl1, acknowledged for its preponderant role in the establishment of
the dorsal root ganglia (DRG)-spinal cord pain circuitry. It was recently suggested that
Tlx3, another homeodomain transcription factor that highly co-localizes with Prrxl1, is
required to maintain Prrxl1 expression in the spinal cord. In order to understand how
the expression of Prrxl1 is regulated by Tlx3, the Prrxl1 promoter sequence was cloned
in a luciferase-reporter vector and its activity was measured after overexpression of
Tlx3 and Prrxl1, together or alone, in the DRG-derived cell line ND7/23. Prrxl1
overexpression, per se, did not seem to result in a significant alteration of the
luciferase activity. Overexpression of Tlx3 led to a 22-fold induction while Prrlx1 and
Tlx3 simultaneous overexpression resulted in a 42-fold luciferase induction. On the
other hand, Prrxl1 silencing reduced in three times the inductive effect produced by
Tlx3 overexpression which pointed to a coordinated action of these transcription
factors in the regulation of the Prrxl1 gene, much likely by the formation of
heterocomplexes. This assumption was confirmed by co-immunoprecipitation assays.
All together, our results suggest that Tlx3-Prrxl1 interaction is required to control Prrxl1
expression.
ERYTHROPOIETIN
REACHES
THE
RETINA
AFTER
SUBCONJUNCTIVAL
ADMINISTRATION
Resende AP (1), SãoBraz B (1), Delgado E (1)
(1) CIISA, Faculdade de Medicina Veterinária, Universidade Técnica de Lisboa
Purpose: Erythropoietin (EPO), a naturally occurring cytokine known by its
erythropoietic properties, has been recently shown to have neuroprotective and
neuroregenerative effects. EPO is actually considered a promising therapeutic agent for
ischemic retinal diseases, such as glaucoma, where the retinal ganglion cells (RGCs)
death results in the progressive loss of visual function. All the previous studies used
the systemic, intravitreal or retrobulbar administration route to achieve therapeutic
concentrations on the retina, difficult to use in clinical practice. We aimed to
investigate the subconjunctival injection as an alternative ocular delivery route for EPO
administration.
Results: The evaluation of EPO expression after subconjunctival administration yielded
an immunostaining signal in the rat’s retinas. Twelve hours after the subconjunctival
administration, EPO was detected in all retinal cell layers, showing a higher
concentration in the photoreceptor layer. Twenty four hours after EPO administration
the signal was concentrated in the RGCs layer and 36 hours after EPO administration
the presence of the protein, detected by immunohistochemistry, was residual. EPO was
not detected in any of the control eyes.
Conclusion/Discussion: After subconjunctival injection EPO reached all the neuroretinal
cell layers in an animal rat model. Our findings prove that the subconjunctival
administration is a possible alternative EPO ocular delivery route. Further studies are
necessary to assess the kinetics of subconjunctival administration of EPO, both in
physiological conditions and ischemic ocular disease conditions.
87
RAPID PERCEPTION OF OLFACTORY INTENSITY CUES
Resulaj A (1,2), Rinberg D (1)
(1) University of Cambridge, United Kingdom; (2) HHMI Janelia Farm Research
Campus, United States
Odor concentration is an important cue for localizing odor sources, from searching for
food and mates to avoiding predators. However, little is known about how olfactory
systems encode odor concentration. We found that mice could discriminate the
different odor concentrations, with an accuracy of around 75%, in as little as 80 ms
after odorant inhalation. This is an unprecedented speed for olfaction and is fast even
by the standards of other sensory modalities. We attribute this new insight into
olfactory perception to our choice of motor output, accurate sniff measurement, and
precise stimulus control. This result suggests that odor-based decisions can be very
rapid and based on information over a very brief temporal window.
THE ROLE OF ADENOSINE A2A RECEPTOR ON NEURONAL OUTGROWTH
Ribeiro FF (1,2), Silva R (3), Fernandes A (3), Brites D (3), Ribeiro JA (1,2), Sebastião
AM (1,2)
(1) Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de
Lisboa, Portugal; (2) Unidade de Neurociências, Instituto de Medicina Molecular,
Lisboa, Portugal; (3) iMed.UL – Faculdade de Farmácia, Universidade de Lisboa,
Portugal.
The objective of this study is to unveil the role and the mechanism of action of
adenosine A2A receptor (A2AR) on neuronal outgrowth. E18 forebrain neurons from
Sprague-Dawley rats were seeded at 40000 cells/mL and treated, at DIC 3, with the
A2AR agonist, CGS 21680, which remained in the medium for at least 5h. Cells stained
with anti-MAP2 and DAPI were submitted to a morphometric analysis by HCA-Vision
software, where it was shown an A2AR induced increase (n = 4) in maximal neurite
length, which corresponds to axon elongation, as observed by an anti-tau1 antibody.
For each independent culture (n), fifty neurons were counted per condition. The
inhibitors of PI3K, MAPK and PLC-gamma signalling pathways, added 30 minutes
before CGS 21680, fully prevented the effect of the A2AR agonist upon maximal
neurite elongation, while PKA inhibition only caused a partial blockade. Data suggest
that A2AR activation promotes axonal elongation through PI3K, MAPK and PLC-gamma
signalling pathways.
BDNF was a gift from Regeneron, USA; Supported by FCT, Portugal.
88
THE ELECTROPHYSIOLOGICAL SIGNATURE OF MOMENTARY LAPSES OF ATTENTION
Ribeiro MJ, d’Almeida OC, Silva E, Castelo-Branco M
Visual Neuroscience Laboratory, IBILI, Faculty of Medicine, University of Coimbra,
Portugal
Detection of threshold stimuli is associated with the pre-stimulus amplitude of brain
oscillations. In this study, we aimed to determine if the amplitude of brain oscillations
could also predict failures in detection of random suprathreshold visual changes
associated with momentary lapses of attention. We used a Neuroscan system to
measure event related EEG/ERP activity during a visual detection task. Participants
were instructed to respond, through button presses, to changes in luminance of a
central fixation square that occurred at random times every 3-10 sec. In most of the
trials, the participants responded correctly. However, on average, participants failed to
respond in 18 % of trials (attentional lapses). We found a significant difference in the
amplitude of brain oscillations when comparing the pre-stimulus periods of detected
and missed trials, with higher amplitudes associated with missed trials. This significant
difference was observed in frequency bands from 1 to 90 Hz: delta, theta, alpha, beta
and gamma, in line with the idea that the amplitudes of the different frequency bands
are correlated and co-modulate with brain states. In conclusion, our data suggest that
momentary lapses of attention are related with neural states characterized by
increased oscillatory activity in a broad range of frequencies.
SOCIAL MODULATION OF FEAR EXTINCTION
Elizabeth Rickenbacher and Marta Moita
Champalimaud Centre for the Unknown, Lisbon, Portugal
Fear responses are innate behaviors exhibited by animals to aversive stimuli. These
responses are what allow animals to behave optimally when their well-being is
threatened. An animal can learn to fear an initial neutral stimuli (ex. tone) when it is
repeatedly paired with an aversive one (ex. footshock). The fear response to the
neutral stimulus can later be extinguished by learning a new non-aversive association.
The aim of this project is to investigate how social interactions might modulate the
learning of the new non-fearful response (extinction). Extinction learning is mediated
by structures that regulate the output from the central nucleus of the amygdala (CeA),
which controls fear responses. We will investigate how social interactions modulate
extinction learning. Since oxytocin and vasopressin have opposite effects on fear and
anxiety related social behaviors, we will focus on these neuropeptides and their role in
the modulation of CeA activity.
Here we propose that social interaction during extinction from fear conditioning causes
the modulation of oxytocin and vasopressin in the CeA, resulting in stronger extinction
learning. The objectives of this project will allow us to contribute important knowledge
pertaining to social modulation of fear behaviors, underlying causes of anxiety
disorders, and possible treatment applications of these disorders.
CO-ORDINATION OF LAYER-SPECIFIC POSITIONING BETWEEN DIFFERENT NEURON
POPULATIONS IN THE DROSOPHILA OPTIC LOBE
Richardson ECN (1), Bell DM (2), and Salecker I (1)
(1) Division of Molecular Neurobiology and (2) Confocal Image Analysis Laboratory,
MRC National Institute for Medical Research, The Ridgeway, London, United Kingdom
Layer-specific positioning of neuronal projections is a conserved feature of neural
network development, yet little is known about how targeting of different neuronal
populations is co-ordinated. Using the Drosophila optic lobe, we have investigated how
the positioning of the temporary layer of R8 photoreceptor axons in the medulla
neuropil, is co-ordinated with the targeting of a novel subset of medulla neurons that
express the isletH (islH) enhancer (Thor and Thomas 1997) during early pupal
development. We show that the cell bodies of the islH neurons migrate towards the
medulla neuropil, while their neurites undergo remodelling and morphological changes
as they grow into the medulla neuropil. We have evidence that the migration and
remodelling are regulated non-autonomously by steroid hormone signalling mediated
via the ecdysone receptor (EcR) in glial cells. Inhibition of the EcR, in particular in the
medulla cortex glia, delays migration and remodelling of islH neurons, but does not
prevent their growth into the medulla neuropil. This is accompanied by expanded
expression of cell surface molecules associated with the medulla neuropil. We propose
that ecdysone signalling is required for timely remodelling of medulla neurons to
properly position the temporary R8 layer at the medulla neuropil border.
DYNAMICS OF SPARSE CODING IN THE FACE NETWORK
van Rijsbergen N.J, Gross J and Schyns PG
Centre for Cognitive Neuroimaging, Institute for Neuroscience and Psychology,
University of Glasgow, Glasgow, UK
Successful object categorization requires the brain to massively reduce the initial
sensory representation into a lower-dimensional coding scheme that supports higherlevel cognition. We examined where, when and how the brain derives such sparse
codes for the biologically relevant categories of seven facial expressions. Five
observers performed 21,000 expression categorization trials of stimuli sub-sampled
with
‘Bubbles’
(randomly
distributed
Gaussian
apertures),
during
Magnetoencephaolgraphy. We performed a beamformer source analysis, computing a
single trial time series of 400 milliseconds for every cortical voxel, before moving to a
mutual information framework, that enabled us to identify where and when the voxels
were sensitive to expression information. We identified networks of sources
contributing simultaneously to correct classification by clustering the mutual
information (MI), between correct/incorrect decision, and voxel signal. We show a
temporal series of cortical ‘macro-states’, associated with the outcome of the
observer’s decision. These cortical macro-states overlap, but are not limited to the right
occipital temporal cortex and Fusiform gyrus. For each expression, 3-4 of these macrostates are also associated with high mutual information between cluster activity and
diagnostic information in the visual input computed as MI(pixel|source). For each
cluster, we show how sensitivity to diagnostic information across voxels evolves across
time.
89
90
IS THE NEUROMUSCULAR TRANSMISSION OF THE SOD1G93A MOUSE, A MODEL OF
AMYOTROPHIC LATERAL SCLEROSIS, COMPROMISED?
Rocha MC (1), Pousinha PA (1), Sebastião AM (1), Ribeiro JA (1), Correia AM (1,2)
(1) Institute of Pharmacology and Neurosciences, Faculty of Medicine and Unit of
Neurosciences, Institute of Molecular Medicine, University of Lisbon; (2) Museu
Nacional de História Natural, Universidade de Lisboa
Amyotrophic Lateral Sclerosis is the most frequent adult-onset motor neuron disease.
Growing evidences suggest that degeneration may begin at the distal axon proceeding
in a dying-back pattern. It seems therefore of interest to investigate synaptic
transmission at the neuromuscular junction in pre- and symptomatic phase of the
disease. Evoked (EPPs) and spontaneous (MEPPs + Giant_MEPPs) activity was
assessed from innervated diaphragm muscle fibers of SOD1G93A mice (tg) and nontransgenic littermates (wt). The Quantal Content (QC) was estimated as the ratio of
the mean EPPs to the mean MEPPs.
In the pre-symptomatic phase, the mean amplitude of EPPs, QC and frequency of
spontaneous events (fSE) were significantly increased in tg mice (EPP:22±2.13mV,
QC:34±2.85, fSE:1.05±0.18s-1;n=11) when compared to wt mice (EPP:14±2.27mV,
QC:26±2.45, fSE:0.58±0.08s-1;n=11). In the symptomatic phase those three features
were slightly decreased in tg animals, but no statistical significance was reached.
Those differences are not related to changes in resting membrane potential since this
parameter remains unchanged among groups.
Altogether, these results suggest that before disease onset there is an enhancement in
neuromuscular transmission, an effect that can be a compensatory response to an
early neuromuscular degeneration. In the symptomatic phase neuromuscular
transmission seems to be compromised.
SINGLE-NEURON MECHANISMS OF TEMPERATURE COMPENSATION IN THE LOCUST
AUDITORY SYSTEM
Roemschied FA, Eberhard MJB, Ronacher B, Schreiber S
(1) BCCN Berlin, Germany; (2) HU Berlin, Germany
Temperature influences basic neuronal properties such as spike rate, amplitude, and
conduction velocity. Here, we investigate temperature effects on signal processing in
the grasshopper acoustic communication system, which is used for partner selection.
Song recognition is initialized within a three-layer feed-forward network comprising
receptor neurons, local and ascending interneurons, respectively.
We intracellularly recorded responses of neurons within the locust auditory system (an
electrophysiologically easily accessible grasshopper model system) at all three
processing stages to acoustic noise stimuli at behaviorally relevant temperatures. We
computed temperature coefficients of neuronal response properties and confirmed an
influence of temperature on spike rate, shape, duration, and latency. However,
receptor neuron and ascending interneuron spike rate was surprisingly close to
temperature-invariance.
Since receptor neurons constitute the bottom layer of the network and therefore do
not receive network input, temperature-invariance presumably is receptor-intrinsic. To
understand this effect, we investigated how temperature-invariance of spike rate could
be achieved in conductance-based neuronal models with temperature-dependent ion
channel dynamics. We propose ionic mechanisms that can lead to temperatureinvariance of spike rate and therefore represent candidate models for receptor neurons
of the grasshopper auditory system.
91
92
NEURONAL DYNAMICS UNDERLYING SELF-GENERATED BEHAVIOURS IN ZEBRAFISH
LARVAE
Romano SA, Sumbre G
Section de Neurosciences, Institut de Biologie de l'École Normale Supérieure (IBENS),
Paris, France.
In a state of sensory deprivation, brain areas show activity patterns. Once interpreted
as irrelevant random noise, these activities have been found to exhibit highly coherent
spatiotemporal structures that could resemble patterns observed during neuronal
processing of sensory stimuli. However, the relationship between ongoing neuronal
activity and self-generated behaviours still remains elusive.
To address this issue, we are currently filming spontaneous tail movements of headrestrained zebrafish larvae while monitoring brain activities using two-photon imaging
of both calcium sensitive dyes and genetically encoded indicators. This method allows
recording the dynamics of large neuronal circuits, with single-cell resolution, from
several brain areas. We are applying dimensionality reduction techniques and
clustering analysis to describe the network dynamics and the flow of activity among
neuronal ensembles that best correlate with self-generated motor behaviours.
Preliminary results indicate a clear structure in the ongoing neuronal activity of the
optic tectum that follows its retinotopic organization, arguing for its possible
behavioural relevance. Moreover, the activation of determined neuronal ensembles
seems to be correlated with the kinematics of specific self-generated motor
behaviours. Distinct behavioural states seem evident, and the neuronal substrate for
this behavioural switching is currently under study.
CELL-TYPE
SPECIFIC
ADENOSINERGIC
MODULATION
OF
PERISYNAPTIC/EXTRASYNAPTIC GABAA RECEPTORS IN THE HIPPOCAMPUS
Rombo DM (1, 2), Dias RB (1, 2), Ribeiro JA (1, 2), Sebastião AM (1, 2)
(1) Instituto de Farmacologia e Neurociências, Faculdade de Medicina da Universidade
de Lisboa, Portugal; (2) Unidade de Neurociências, Instituto de Medicina Molecular,
Portugal
A diverse population of GABA releasing neurons cooperates in the brain to regulate
excitabilitya. A tuned modulation of inhibitory responses is of great importance in the
control of network function. One such strong modulator of synapses is adenosine,
which controls glutamatergic transmission in the hippocampus through high-affinity A1
and A2A receptorsb. However, the role of adenosine on inhibitory transmission is much
less known.
We used the patch-clamp technique to record synaptic and extrasynaptic/perisynaptic
GABAA-mediated currents from different types of neurons in rat hippocampal slices.
Our results show that adenosine, through activation of A1 receptors, controls the
function of GABAA receptors localized at perisynaptic/extrasynaptic compartments,
without affecting the function of GABAA receptors localized at the synaptic
compartments. This effect is evident in the majority of CA1 pyramidal cells and in a
subpopulation of s.radiatum and s.oriens interneurons. However, there are no evident
differences in the morphologic and physiologic features between the responding and
non-responding interneurons.
Together, these results indicate that A1 receptor actions on GABAA receptor function is
cell type specific and mainly occurs at the perisynaptic/extrasynaptic level.
Support: FCT.
References:
a
Somogyi P and Klausberger T, 2005, J.Physiol, 562,9-26
b Ribeiro JA and Sebastião AM 2010, Acta.Physiol (Oxf), 199,161-9.
NEURONAL ACTIVITY DYNAMICS IN CORTICO-STRIATAL CIRCUITS DURING MOTOR
SKILL LEARNING
Santos FJ (1,2), Costa RM (1)
(1) Champalimaud Neuroscience Programme, Portugal; (2) International Neuroscience
Doctoral Programme, Portugal
To investigate the neural correlates of motor learning, we implanted multielectrode
arrays to record simultaneously neural activity in the primary motor cortex (M1) and
dorsolateral striatum (DLS), while mice learned and performed an operant task, in
which they are required to perform sequences of actions to obtain rewards. We started
recording neural activity 12 hours before the first session and continuously recorded
throughout four days of training, for a total of more than 100 hours. We managed to
monitor activity of some cells through the whole learning process. The percentage of
neurons with lever-press related activity in DLS increased significantly with training,
with many neurons showing a decrease in firing rate. This was not observed in M1. We
next investigated the correlation/variation in neuronal ensemble activity between
sequences in the same session, and across sessions using only stable units. Sequenceto-sequence variability decreased in late versus early sessions, with differential timecourses for cortical and striatal ensembles. We also observed that session-to-session
activity gradually changed throughout training, with significant differences between
initial and final sessions. Importantly, overall firing rates did not change with learning.
These data suggest that corticostriatal circuits gradually change during motor-skill
learning until a consolidated neuronal ensemble activity pattern emerges.
NEURONAL AND BEHAVIORAL CORRELATES OF TIME ESTIMATION IN RUNNING RATS
Rueda-Orozco PE and Robbe D
IDIBAPS, System Neuroscience Department, Barcelona, Spain
Neuroimaging, pharmacological and neurophysiological studies in humans and rodents
point to the dorsal striatum as a brain region that provide with a critical contribution to
the capacity of estimating time, at the timescale of a few seconds. Exactly how
neurons in the striatum contribute to this behavioral function is unclear. An attractive
hypothesis is that animals use sequence of movements to estimate time. In this
framework, neuronal activity in the striatum would control the kinematic of this
embodied time estimation.
To test this hypothesis we developed a time estimation task for rats while they run at
moderate speeds (40cm/sec) on a treadmill. The task required from the animals to run
at least 7 seconds and stop the treadmill by passing their head in front of a salient
photo-detector. In short, successful performance required the animals to modulate
their running speed in a timely manner. Additionally, tetrode recordings were
performed in the dorsolateral striatum during the task. We found that in a significant
proportion of the striatal neurons recorded (>30%), firing rate and running speed were
correlated. Ongoing experiments are performed to test that this neuronal correlate of
the dynamic of locomotion plays a causal role in time estimation.
THE UBIQUITIN-PROTEASOME SYSTEM IS REGULATED BY BDNF AT HIPPOCAMPAL
SYNAPSES
Ana Rita Santos, Miranda Mele, Blanka Kellermayer, Diogo Comprido, Bruno J
Manadas, Carlos B Duarte
Center for Neuroscience and Cell Biology, Department of Life Sciences, University of
Coimbra, Coimbra, Portugal
BDNF is a neurotrophin playing important roles in synaptic plasticity, neuronal
development, and in cell survival. We recently showed that BDNF exerts a fine control
of the proteome in hippocampal neurons by modulating the intricate balance of protein
synthesis and degradation. We found that BDNF regulates several components of the
UPS, as shown by gene and protein expression studies. Furthermore, BDNF downregulated the proteasome activity in cultured hippocampal neurons and in
synaptoneurosomes. The protein levels of Uch-L1, a deubiquitinating enzyme, were
also regulated by BDNF and experiments addressing its specific activity showed that
the neurotrophin specifically activates Uch-L1 at the synapse. The maintenance of a
free ubiquitin pool is determinant for the normal neuronal function, and is controlled by
the activity of both the proteasome and deubiquitinating enzymes. The levels of free
ubiquitin in synaptoneurosomes were transiently reduced upon short (15-30 min)
stimulations with BDNF. These changes in the activity of the UPS and the consequent
alterations in the amount of free ubiquitin may modulate the ubiquitination state of
some synaptic proteins. The coordination of two opposing limbs (protein translation
and degradation) may account for the multiple roles of BDNF in the central nervous
system.
Supported by FCT and FEDER
93
94
FINE-TUNING OF PLASTICITY BY ADENOSINE A2A RECEPTORS AT THE TRIPARTITE
SYNAPSE
Sebastião AM
Institute of Pharmacology and Neurociences, Faculty of Medicine and Unit of
Neurosciences, Institute of Molecular Medicine, University of Lisbon, Portugal
Fine-tune control of neuronal communication involves a network of modulators that
affect neuron and glia in a concerted way. The group has been obtaining evidence
clearly showing that adenosine A2A receptors (2ARs) fine-tune neuronal activity
allowing excitability reinforcement and plasticity and I will refer to it. A2AR blockade in
vivo prevents hippocampal-dependent conditional learning and synaptic facilitation
recorded concomitantly. A2AR facilitate extrasynaptic AMPAR responses, enhance
expression of GluR1-containing AMPAR at surface membranes and facilitate LTP.
Furthermore, A2A receptors may contribute to a decrease in tonic inhibition since they
facilitate uptake of GABA into nerve terminals and astrocytes, as well as allow the
facilitatory action of BDNF upon astrocytic GABA uptake. A2ARs allow BDNF action in
aged animals, trigger synaptic BDNF facilitatory actions in very young animals and
facilitate BDNF actions upon LTP, inducing translocation of TrkB receptors into lipid
rafts. A2AR permit TrkB inhibitory actions upon alfa-7 nicotinic responses in
interneurons and in this way may contribute to tune cholinergic facilitatory inputs to
inhibitory neurons. In addition, A2ARs control extracellular levels of its endogenous
ligand enhancing the activity of membrane located equilibrative nucleoside
transporters. In conclusion A2AR exert concerted actions at the tripartite synapse,
having impact upon plasticity and behaviour.
NEURONS AFFECTING GROOMING BEHAVIOR IN DROSOPHILA
Andrew M. Seeds and Julie H. Simpson
Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn
How different brain regions coordinate to drive stereotyped motor tasks while remaining
plastic enough to respond to changing environmental cues remains an important area of
study. We focus on fruit fly grooming behavior combined with facile Drosophila genetics as
a model for studying how nervous systems generate and modulate complex motor
behaviors. Mechanosensation of debris on specific body parts induces stereotyped cleaning
movements characterized by site directed leg sweeps. We find evidence that these
movements are regulated as part of a higher order structure as placement of dust on the
entire body reveals a prioritization of head cleaning over that of posterior body parts. We
performed a high-throughput cleaning assay with Drosophila tools for disrupting
neurotransmission in genetically selected subsets of neurons (GAL4/UAS system) to identify
circuitry driving grooming behavior. Disruption of different regions of the nervous system
causes failure to clean discrete body parts and/or impairs the coordinated progression of
grooming. Additionally, secondary analysis of the grooming defective GAL4 lines using
neural activators uncovered neurons that are sufficient to drive discrete modules of
grooming behavior. Anatomical and behavioral studies reveal that the majority of grooming
movements are driven from distinct neuropiles in the ventral nerve cord but the normal
progression of grooming behavior requires neural components in the brain. We identified
sensory inputs projecting to either the brain or ventral nerve cord that are sufficient to
evoke grooming movements and are testing downstream candidate neurons for their roles
in either driving grooming movements or coordinating with the rest of the nervous system.
We postulate that grooming circuitry consists of local networks of neurons that act
autonomously to drive specific components of the behavior and interneurons connecting
these local modules to coordinate a cleaning response.
95
NEURAL ACTIVITY-DEPENDENT MECHANISMS REGULATING RADIAL GLIA MOTILITY
Sild M, Ruthazer ES
Montreal Neurological Institute, McGill University, Montreal, Canada
Neurons and glia cells are by now understood to engage in constant two-way
communication. A subtype of glial cells called radial glia have been demonstrated to
participate in a wide number of different functions like neuron migration, axon
guidance and synapse formation. However, the mechanisms of these interactions
remain poorly understood. Our published data has revealed that radial glia respond to
neural activity by modifying both the rate of intracellular calcium transients and their
filopodial probing of the environment. We have focused on elucidating the details of
this neuron-glia interaction by imaging glial cell behaviour in the living intact Xenopus
tadpole brain by two-photon microscopy. We propose that signaling from neurons to
glia involves synaptic activity-dependent nitric oxide release from the neurons leading
to cGMP-dependent protein kinase G (PKG1) activation in the glia that in turn regulates
downstream cytoskeleton modifying proteins. We have demonstrated, that
manipulating PKG1 activity affects glia motility. Furthemore, our data show that
compromising PKG1 function perturbs the interpretation of neural activity-derived
signals by glia. We can conclude, that PKG1 is an important regulator of neural activitydependent behaviour in glia having a role in translating synaptic activity levels to
changes in glia process motility.
A THREE-DIMENSIONAL MRI BRAIN ATLAS OF THE MOZAMBIQUE TILAPIA
(OREOCHROMIS MOSSAMBICUS)
Simões JM (1,2), Verhoye M (3,4), Van der Linden A (3), Teles M (1,2), Oliveira
RF(1,2)
(1) Unidade de Investigação em Eco-Etologia, ISPA, Lisboa, Portugal; (2)
Champalimaud Neuroscience Programme, Instituto Gulbenkian de Ciência, Oeiras,
Portugal; (3) Bio-Imaging Lab, University of Antwerp, Antwerp, Antwerp, Belgium; (4)
Vision Lab, University of Antwerp, Antwerp, Antwerp, Belgium
The African cichlid Oreochromis mossambicus, has been used as a model system in a
wide range of studies. The increasing number of genetic tools available for this
species, together with the emerging interest in its use for neurobiology studies,
increased the urgency in an accurate hodological mapping of the tilapia brain to
complement the available histological data. The goal of our study was to elaborate a
three-dimensional, high-resolution digital atlas using magnetic resonance imaging.
Resulting images can be viewed and analysed in all orientations (coronal, sagital, and
horizontal) and were manually labelled to reveal major brain nuclei in the olfactory
bulb, telencephalon, diencephalon, optic tectum, and cerebellum. In this study, a 9.4T
MR Bruker Biospec system (Bruker, Germany) was used to acquire T2-weighted 3D
RARE images of 3 adult male tilapia brain (perfused with Paraformaldehyde +
Dotarem® (4%)) immersed in Fluorinert (3M Co., Ltd.). The sequence timings were
TE=36ms and TR=350ms. The voxel resolution of the 3D digital atlas was
(50x50x50)µm3. Image labelling and three-dimensional surface reconstructions were
created using dedicated software (Amira, Mercury Computer Systems, USA). This high
resolution tilapia brain atlas is expected to become a very useful tool for
neuroscientists using this fish model and will certainly expand their use in future
studies of the CNS.
96
MICE CAN SMELL TIME
Smear MC (1,2), Shusterman R (1), O'Connor RP (3), Bozza TC (1,2), Rinberg D (1)
(1) HHMI/JFRC Ashburn, VA, USA; (2) Northwestern University Evanston, IL, USA, (3)
Boston University Boston, MA, USA
Olfactory systems encode odours not only by which neurons respond, but when they
respond. In mammals, every sniff evokes a precise, odour-specific sequence of activity
across olfactory neurons. Likewise, in a variety of neural systems, from sensory
periphery to cognitive centers, neuronal activity is timed relative to sampling behavior
and/or internally-generated oscillations. As in these systems, mammalian olfaction may
use phase coding to represent information. However, there is no evidence that
mammalian olfactory systems read such cues. To test whether mice perceive the
timing of olfactory activation relative to the sniff cycle (sniff phase) we used
optogenetics in gene-targeted mice to generate spatially-constant, temporallycontrollable olfactory input. Here we show that mice can "smell time" -- that is,
behaviorally report the sniff phase of optogenetically-driven OSN input. Furthermore,
mice smell time acutely, discriminating shifts in input timing as little as 10 ms, similar
to the temporal precision of olfactory bulb (OB) odour responses. Electrophysiological
recordings in the OB of awake mice show that individual cells encode sniff phase of
photoactivation in both the timing and amplitude of their responses. Our work provides
the first evidence that the mammalian olfactory system can read temporal patterns,
and suggests that timing of activity relative to sampling behavior is a potent cue which
may enable accurate olfactory percepts to form quickly.
STORING INFORMATION IN MEMBRANE CONDUCTANCES DYNAMICS – WORKING
MEMORY WITHOUT SYNAPTIC PLASTICITY
Sousa E, Aguiar P
Faculdade de Ciencias da Universidade do Porto, Portugal; Centro de Matematica da
Universidade do Porto, Portugal
Certain brain regions have the ability to retain information for periods of many seconds
after the original stimuli have been removed. This short-term storage of information
may serve as a buffer supporting information processing, and is known as working
memory. Most existing models describing working memory rely on synaptic plasticity
mechanisms to support information storage. However, most known synaptic plasticity
mechanisms work on time scales which are too slow for the working memory
requirements.
In this study we propose a working memory model which does not rely on synaptic
changes. We show that the interplay between long-lasting calcium channels, calcium
activated non-specific cationic currents and NMDA synapses can produce populations
of neurons capable of storing information in their membrane conductances dynamics.
Multiple patterns of activity can be simultaneously stored in the same population using
different synchronization time-frames. Our model contains three types of neurons, one
principal excitatory population and two classes of inhibitory interneuron populations, all
described by the Hodgkin-Huxley formalism. The assumed architecture is consistent
with the neuronal connectivity present in cortical columns. All simulations were
performed in the NEURON software.
MAPPING OF PRRXL1 INTERACTION DOMAINS WITH TLX3
Soares dos Reis R (1,2), Regadas I (1,2), Falcão M (1,2), Pessoa AS (1,2), Monteiro
FA (1,2), Reguenga C (1,2), Lima D (1,2)
(1) Departamento de Biologia Experimental, Faculdade de Medicina, Universidade do
Porto, Portugal; (2) IBMC – Instituto de Biologia Molecular e Celular, Universidade do
Porto, Portugal
The establishment of the nociceptive system is governed by a transcription factor
network of which several key-players have been identified such as the homeodomain
proteins Prrxl1 (also known as Drg11) and Tlx3. They act to regulate cell fate and
neuronal connectivity. Recently, we demonstrated that the interaction of Prrxl1 with
Tlx3 enhances Prrxl1 expression.
To identify the Prrxl1 domain responsible for Tlx3 interaction, several N-terminus and
C-terminus truncated Prrxl1 constructs were generated. Transcriptional activity (Prrxl1
and Prrlx1 plus Tlx3) assays, using a luciferase-reporter, and protein-protein interaction
studies, using co-immunoprecipitation followed by immunoblotting against Tlx3, were
performed.
Truncation of Prrxl1 C-terminus (deletion from the aminoacid residue 227 onwards)
hampered its repressor activity and further truncation resulted in induction of
transcription. The transcriptional interaction with Tlx3 was weakened when different
Prrxl1 C-terminus lacking constructs were expressed. The C-terminal region alone
exhibited Tlx3 binding, albeit at reduced levels when compared to wild-type. Moreover,
a Prrxl1 mutant with impaired DNA-binding activity displayed reduced Tlx3 binding.
Altogether, our data suggest that Prrxl1 C-terminus modulates its transcriptional
activity and is required for Tlx3 binding. Furthermore, Prrxl1-Tlx3 interaction seems to
be dependent on DNA-binding.
TOWARDS BIOPHYSICALLY REALISTIC MODELS OF THE NEURONAL DYNAMICS IN
THE RETICULAR NUCLEUS OF MEDULLA OBLONGATA
Sousa M (1,2), Aguiar P (3), Szucs P (1)
(1) Instituto de Biologia Molecular e Celular, Portugal (2) Faculdade de Medicina do
Porto, Portugal (3) Centro de Matemática da Universidade do Porto, Portugal
Understanding the dynamics of the transmission and processing of nociceptive
information at the spinal level is of unquestionable importance. This work is part of a
large project focusing on better understanding the bidirectional pathway between
reticular nucleus of medulla oblongata neurons and spinal dorsal horn lamina I
neurons. Here we present preliminary results from a combination of experimental and
theoretical approaches to identify and analyze different functional classes of neurons
present in the reticular nucleus.
Brainstem blocks were prepared by making one transverse cut through different levels
of the reticular nucleus, preserving most of the cell processes and connections.
Neurons were visualized using the IR-LED technique and whole-cell patch-clamp
recordings were performed from the cut surface. In addition to electrophysiological
data collection, this approach allowed the labeling of the recorded neurons with
biocytin for consecutive 3D reconstruction and morphological analysis. Such
electrophysiological and detailed anatomical data is crucial for the construction of
realistic models.
The Hodgkin-Huxley formalism was used to build single compartment models
recreating the core membrane dynamics features, together with the patterns of firing
activity, of the recorded reticular nucleus neurons. These models were used to infer
parameters that were not obtained experimentally.
97
98
PHASE OF INFRAGRANULAR ALPHA OSCILLATIONS MODULATES AMPLITUDE OF
GRANULAR AND SUPRAGRANULAR GAMMA OSCILLATIONS IN MONKEY V1
Spaak E, Bonnefond M, Maier A, Leopold DA, Jensen O
(1) Radboud University Nijmegen, Donders Institute for Brain, Cognition, and
Behaviour, Centre for Cognitive Neuroimaging, The Netherlands; (2) Unit on Cognitive
Neurophysiology and Imaging, Laboratory of Neuropsychology, National Institute of
Mental Health, USA
The alpha (8-12Hz) rhythm is the most prominent oscillatory component visible in
electrophysiological recordings of neural activity, and is thought to be involved in
‘gating’ information, in both sustained and periodic manners. Gamma (30-100 Hz)
oscillations are thought to reflect active cortical processing. Understanding the
interplay between the alpha and gamma rhythms is crucial for understanding the
information processing properties of the cortex. Recently, it has been found that alpha
oscillations are likely generated in the infragranular layers of the cortex, while gamma
oscillations are more prominent in the granular and supragranular layers. To shed light
on the relation between these layer-specific rhythms, we recorded spontaneous activity
from all layers of primary visual cortex in awake behaving macaque monkeys. We
found that gamma amplitude in layers 4 and above was strongly modulated by the
phase of the infragranular alpha rhythm; specifically, gamma amplitude was high
during peaks of the alpha cycle. Furthermore, this phase/amplitude coupling was
dependent upon infragranular alpha power: alpha phase only modulates gamma
amplitude when alpha power is sufficiently strong. These findings suggest a role for
the infragranular alpha rhythm as a regulator of active processing, as reflected by
gamma oscillations in layers 4 and above.
MORE BITS FOR BEHAVIOR: STOCHASTIC DYNAMICS IN THE REVERSAL MOTIONS OF
C. ELEGANS
Greg J Stephens
Princeton University
From the dynamics of single molecules to networks of gene expression, there has been
an explosion in our ability to measure the microscopic components of living systems.
The output behavior of an entire organism, however, is often still characterized by eye.
Here we use high resolution video microscopy to record the motions of the nematode
C. elegans, freely-wiggling on a flat agar plate. We show that the space of shapes is
remarkably low dimensional, with just four dimensions accounting for 95% of the
shape variance. Projections of worm shape along these four "eigenworms" provide a
precise yet substantially complete description of worm behavior, capturing both
classical worm motion such as forward crawling, reversals, and Omega-turns and novel
behaviors such as “pause” states at particular postures. We use the eigenworm
projections to develop a stochastic model of the worm's locomotor wave dynamics that
predicts transitions between attractors corresponding to abrupt reversals in crawling
direction. With no free parameters, our inferred dynamical system generates long
reversal time scales and stereotyped trajectories in close agreement to experimental
observations. Finally, we use our stochastic model to demonstrate that the noise
amplitude decreases systematically with increasing time away from food, resulting in
longer bouts of forward crawling and suggesting that worms use noise to adaptive
benefit.
99
IDENTIFICATION OF ORB2 RNA TARGETS BY ICLIP
Stepien BK, Kruettner S, Gerlach D, Stark A, Keleman K
Institute of Molecular Pathology, Austria
One of the most fundamental questions in neurobiology is the molecular basis of longterm memory formation. Establishment of long-term memory is thought to be
dependent on local translation in order to achieve stable modification of specific
synaptic connections. However, little is known about the molecular players and
mechanisms underlying such changes. Good candidates to perform these functions are
CPEB family of proteins known to regulate translation in early development and
recently shown to be expressed in the nervous system both in vertebrates (mouse)
and invertebrates (Aplysia and fruit fly). Furthermore, the Drosophila CPEB protein,
DmOrb2, was shown to be necessary for the formation of long-term memory.
However, the mechanism by which it could control local translation in this process, as
well as its mRNA targets and binding motif are so far unknown.
To get insights into the mechanism of local translation in long-term memory formation
we use newly developed CLIP (crosslinking and immunoprecipitation) technology to
immunoprecipitate Orb2-RNA complexes and identify by Solexa sequencing and
bioinformatic analysis both potential Orb2 RNA targets and the specific Orb2 binding
motif.
UPDATED METHODOLOGY OF THE CHRONIC STRESS DEPRESSION MODEL:
IMPORTANCE OF INTERNAL CONTROL
Tatyana Strekalova and Harry MW Steinbusch
Department of Neuroscience School for Mental Health and Neuroscience, Maastricht
University, Maastricht, the Netherlands
The reliability of modelling of a depressive-like state using chronic stress is confronted
by significant methodological limitations. We believe that the modifications to the
stress paradigm in mice proposed in our model allow some of these limitations to be
overcome. In a new variant of the chronic stress paradigm, the anhedonic state is
defined by a decrease in sucrose preference that is not exhibited by all individuals. As
such, we propose the use of non-anhedonic, stressed mice as an internal control in
experimental mouse models of depression. The application of an internal control for
the effects of stress, along with optimized behavioural testing, can enable the analysis
of biological correlates of stress-induced anhedonia versus the consequences of stress
alone in a chronic-stress depression model. This was illustrated by distinct physiological
and molecular profiles in anhedonic and non-anhedonic groups. Our findings argue for
the use of a subgroup of individuals who are negative for the induction of a depressive
phenotype during experimental paradigms of depression as an internal control, for
more refined modeling of this disorder in pre-clinical studies.
100
FUNCTIONAL AND MORPHOLOGICAL ANALYSIS OF INHIBITORY PROJECTION
NEURONS OF THE OLFACTORY SYSTEM OF DROSOPHILA MELANOGASTER
Strutz A, Baschwitz A, Hansson BS, Sachse S
Max Planck Institute for Chemical Ecology, Jena, Germany
The olfactory system of the vinegar fly Drosophila melanogaster provides an excellent
system to study coding and processing of sensory information in the brain. Olfactory
sensory neurons (OSNs) transfer peripheral information from the antennae to the
primary olfactory neuropil, the antennal lobe (AL). Within the AL odors are encoded by
specific ensembles of activated glomeruli. The glomerular organization of the AL results
from dense synaptic connectivity between three different neuron types: [1] OSNs
expressing a specific odorant receptor type, [2] local interneurons (LNs)
interconnecting glomeruli in an AL restricted pattern and [3] projection neurons (PNs)
relaying the olfactory information to higher brain centers as the mushroom body calyx
(MB) and the lateral horn (LH). Several studies indicate that the MB but not the LH is
involved in olfactory learning processes. The LH is rather assumed to play a role in
innate olfactory behavior. However, so far direct evidence for this function is still
missing. Excitatory PNs (ePNs), which are mainly uniglomerular send axons to both
regions, the MB as well as the LH. In contrast inhibitory PNs (iPNs, ~45) develop
polyglomerular innervations within the AL and project exclusively to the LH. To analyze
the function of iPNs underlying olfactory coding we performed a morphological
characterization using photoactivated GFP and immunostainings. In addition we
functionally characterized these neurons using calcium imaging in the LH.
Though iPNs innervate only around one third of the AL glomeruli, calcium responses to
a large set of ecologically relevant odors at different concentrations were evoked.
Response patterns in the LH vary according to odor concentration and identity. The
wide range of odors evoking activity in iPNs as well as their spatially segregated output
indeed suggests a function in innate odor quality and intensity coding of the LH.
PROJECTION NEURONS WITH DISTINCT AXON-TRAJECTORIES IN THE LATERAL
SPINAL NUCLEUS AND LATERAL LAMINA I OF THE LUMBAR SPINAL DORSAL HORN OF
RATS
Szucs P (1), Antal Zs (2), Pinho R (1), Antal M (2), Safronov BV (1)
(1) Spinal Neuronal Networks, Instituto de Biologia Molecular e Celular-IBMC, Porto,
Portugal; (2) Dept. Anatomy, Histology and Embryology, University of Debrecen,
Hungary
Although projection neurons (PNs) in lamina I of the spinal cord and in the lateral spinal
nucleus (LSN) are crucial output elements of the spinal nociceptive processing circuitry, we
know very little about their axonal trajectories within the spinal cord.
Thus, we reconstructed the axons of PNs labelled intracellularly in the isolated spinal cord.
We found, that PNs in this region showed distinct axon-trajectories. The majority gave rise
to an axon that crossed the midline in the anterior commissure and ascended in the
contralateral anterolateral tract (ALT). A subset of these neurons gave rise to two long
axon collaterals in the ipsilateral side; one descending in the dorsolateral funiculus, the
other ascending in either the tract of Lissauer or in the dorsal funiculus. Another set of PNs
sent their main axon to the contralateral ALT through the posterior commissure. The main
axon of a yet another group of PNs paid a short visit to the contralateral side, going around
the central canal while giving short collaterals to both sides, and finally ascended in the
ipsilateral ALT.
Our findings indicate that via their local collaterals PNs in this region may play a role in
propriospinal processing of nociceptive information.
101
SENSORY RESPONSE VARIABILITY: BIASING OR REFLECTING PERCEPTUAL
DECISIONS?
Wimmer K (1), de la Rocha J (1), Roxin A (1), Renart A (2), Compte A (1)
(1) IDIBAPS, Barcelona, Spain; (2) Champalimaud Neuroscience Programme, Lisboa,
Portugal
Trial-to-trial variability in the response of cortical sensory neurons to ambiguous stimuli
correlates with variability in the perception. This correlation, usually quantified by the
Choice Probability (CP), has been interpreted to reflect the bottom-up causal role of
neuronal variability on guiding perceptual decisions although recent evidence suggests
that the time course of CP is partially inconsistent with this interpretation. We study
two network mechanisms that generate CP in a network model composed of a sensory
circuit reciprocally connected with a decision circuit: (i) correlated spiking variability in
the sensory population and (ii) top-down inputs from the decision circuit. In a
feedforward version of the model, with large spiking correlations and no top-down
inputs, the CP peaked right after stimulus onset and then decayed slowly to zero. In a
feedback version of the model, with small correlations and top-down inputs, the CP
rose slowly and reached a plateau. Thus, a causal role of correlated spiking variability
would be reflected in the early rise and decay of the CP, while slow CP saturation
mirrors the arrival of the decision circuit to the final choice. In the feedback model, the
top-down input promotes perceptual stability because it amplifies small initial
differences in the response of the sensory populations, which are then sent bottom-up
enhancing the stability of the attractor solution in the decision circuit. Our results help
to elucidate the contribution of feedforward and feedback mechanisms to the
generation of CP.
INVESTIGATING THE ROLE OF STRIATAL SUBCIRCUITS IN THE PERFORMANCE OF
ACTION SEQUENCES USING OPTOGENETICS.
Fatuel Tecuapetla (1,2), Xin Jin (3), Rui Costa (1,2)
(1) Instituto Gulbenkian de Ciencia, Portugal; (2) Champalimaud Center for the
Unknown, Portugal; (3) National Institute on Alcohol Abuse and Alcoholism, NIH, USA
The basal ganglia have been implicated in the control of action sequences. The
striatum, the main input to the basal ganglia is composed of at least four different
subtypes of neurons. We investigated the role of the striatal subtypes in the
performance of self-paced action sequences by manipulating their activity using
optogenetics.
We trained mice in a task in which animals have to press 8 times to get a reward,
which results in the development of stereotypical sequences. We used
channelrhodopsin 2 (ChR2) to manipulate the firing of the striatal neurons optically
while the animals perform the task. The specificity of the ChR2 driven spikes in the
striatal subtypes neurons was obtained by striatal injections of adeno-associated virus
with Cre-dependent ChR2-EYFP expression into D1-Cre, D2-Cre, Chat-Cre and PV-Cre
mice (expressing Cre recombinase in D1 or D2 dopamine receptors expressing
neurons, cholinergic and parvalbumin interneurons, respectively). Our data shows that
activation of specific neostriatal subcircuits either before or after sequence initiation
affects different aspects of action sequence execution like sequence initiation,
sequence length, and sequence termination.
102
SOCIAL MODULATION OF ADULT NEUROGENESIS IN THE NEURAL NETWORK
UNDERLYING AGGRESSIVE BEHAVIOR IN ZEBRAFISH
Magda Teles (1,2), Daniel A. Peterson(3), Rui F. Oliveira (1,2)
(1) Unidade de Investigação em Eco-Etologia, ISPA, Lisboa, Portugal; (2) Champalimaud
Neuroscience Programme, Instituto Gulbenkian de Ciência, Oeiras, Portugal; (3) Neural
Repair and Neurogenesis Laboratory, Department of Neuroscience, The Chicago Medical
School at Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
In social systems, animals adjust their social behaviour according to available information
in the social environment. The “core” neural circuits underlying social behaviour are
composed of a network of forebrain and midbrain nuclei with reciprocal connections, the
social behaviour network (SBN). This brain network is differentially activated with singular
behaviours leading to distinct patterns of response across the nodes, which ultimately lead
to behavioural plasticity. Recent evidence suggests that adult neurogenesis is a driving
force for this plasticity and that interactions can alter adult neurogenesis in vertebrates and
invertebrates species. For example exposure to an acute psychosocial stressor decreased
number of newly generated cells in the hippocampus. These data support the idea that
adult neurogenesis has a powerful machinery acting on the rearrangement of the brain
networks underlying social behaviours. In the present work we investigate the influence of
social experience in the SBN and how changes in SBN can modulate the expression of
different behavioural phenotypes, with particular focus on environmental regulation of
neurogenesis. For this purpose, we studied agonistic interactions to establish social
dominance in zebrafish. A simple protocol was used with pairs of males where animals
could experience winning the interaction, losing the interaction, have an unsolved
interaction or experience no interaction. In a first set of experiments, each node of the
SBN was microdissected and the expression of several neurogenic genes, including Wnt3,
BDNF, NeuroD1, and caspase 3 were characterized in the different behavioural conditions.
In a second set of experiments animals were injected with BrdU immediately after the
social interaction in order to characterize proliferation and short-term survival of the
newborn cells in the same nuclei (SBN). For short-term survival BrdU
immunohistochemistry was also combined with immunolabeling against DXC and Caspase
3 and high-throughput confocal stereology was used to determine the number of cells
undergoing neuronal commitment or apoptosis. This study will establish the quantitative
response of neuronal plasticity in the SBN network to social changes. Data from the gene
expression study will help establish the important modulators of neuronal recruitment in
response to social interactions in zebrafish.
NETRINS AND FRAZZLED ARE REQUIRED FOR LAYER-SPECIFIC TARGETING OF
PHOTORECEPTOR AXONS IN DROSOPHILA
Timofeev K (1), Joly W (1,2), Hadjieconomou D (1), and Salecker I (1)
(1) MRC - National Institute for Medical Research, UK; (2) Institut de Genetique
Humaine, France
The ability of a nervous system to correctly process sensory information depends on
the precise organization of axonal and dendritic projections into distinct synaptic units
such as columns or layers.
We use the Drosophila visual system as a model to investigate the mechanisms that
regulate layer-specific axon targeting. Photoreceptor neurons (R-cells, R1-R8) extend
axons into the optic lobe. R1-R6 axons target to the lamina, while R8 and R7 axons
terminate in two distinct layers in the medulla, called M3 and M6.
We show that the secreted Netrin ligands and the attractive Frazzled guidance receptor
are crucial for regulating targeting of R8 axons to the M3 layer by providing layerspecific positional information. Netrin-B is expressed by lamina neurons L3, as well as
medulla and lobula neuron subtypes, and is localized in the medulla layer M3. Frazzled
is expressed in R8, as well as target neurons. Loss of both Netrin-A and B results in
similar R8 axon targeting defects as loss of its receptor frazzled in R-cells.
We propose that Frazzled has a dual function in the developing visual system: (1)
layer-specific localization of Netrin-B through target neurons and (2) guidance of R8
axons to their specific target layer M3.
103
104
A SCREEN FOR NEURONS UNDERLYING GAP-CROSSING BEHAVIOR IN DROSOPHILA
MELANOGASTER
Triphan T (1), Roberts SF (1), Korff WL (1), Strauss R (2)
(1) Howard Hughes Medical Institute, Janelia Farm Research Campus, USA; (2)
Johannes Gutenberg-Universtiaet Mainz, Institut fuer Zoologie III – Neurobiologie,
Germany
Drosophila melanogaster exhibit a sophisticated climbing behavior when presented
with a chasm in their walkway (Pick & Strauss 2005). As part of the Janelia Farm Fly
Olympiad Project we are screening flies for defects in gap-crossing behavior.
Thousands of Gal4 lines expressing in subsets of neurons in the brain (Pfeiffer et al.
2008) are crossed to UAS-shibire(ts) to inactivate these neurons. Flies are released
within a set of concentric rings separated by water-filled gaps of increasing width
(2mm to 4mm in steps of 0.5mm). We track the distribution of flies on the rings and
the position and percentage of dead flies in the grooves that failed in climbing and
drowned. To assess the overall climbing ability of a line, we calculate the mean
position of 15 flies over 10min. There are several categories of hits. Some lines stay
close to the center, though the majority cross broader gaps and venture out further.
Several lines show a high number of fatalities at small gaps while others fail at the
largest 4.0mm gap. The hit rate is about 25%, with the majority of lines being motor
impaired or inactive. Hits are analyzed in secondary walking and climbing assays using
high-speed videography.
A WIDE-FIELD NEURON IN THE FLY LAMINA ENHANCES CONTRAST SENSITIVITY
John Tuthill, Aljoscha Nern, Gerry Rubin, Michael Reiser
Howard Hughes Medical Institute, Janelia Farm Research Campus
We have identified a class of novel wide-field neurons in the most peripheral layer of
the fly visual system, the lamina. The distinct anatomical profile of this neuron type
suggests that it could provide feedback to lamina neurons involved in motion
detection. Using a virtual reality flight simulator, we found that silencing lamina widefield (la wf) neurons with an inward rectifier potassium channel (kir2.1) decreased the
fly’s ability to detect low contrast visual motion stimuli. Whole-cell patch-clamp
recordings revealed that la wf neurons have large spatial receptive fields (~30 degrees
of visual space), and are tuned to detect low frequency luminance fluctuations (1-4
Hz). Application of the neuromodulator octopamine increased the excitability of la wf
neurons. Recordings in flying flies indicate that octopamine release during flight
increases la wf sensitivity to higher frequency luminance fluctuations. These
anatomical, behavioral, and electrophysiological data suggest that la wf neurons
enhance contrast sensitivity by providing predictive feedback to motion-detection
pathways in the lamina.
ANATOMICAL ASSOCIATION BETWEEN IMMATURE NEURONS AND PLACE-CELL
ACTIVITIES IN ADULT DENTATE GYRUS
M. Uemura and A Tashiro
Norwegian University of Science and Technology, Kavli Institute for Systems
Neuroscience and Centre for the Biology of Memory
New neurons are continuously generated in adult dentate gyrus and believed to be
involved in memory functions. Newly-generated immature neurons have higher
excitability in vitro and may form an active neuronal population during behaviors, as
suggested by immediate early gene expression in rats after spatial learning. Here, we
explored anatomical relationships of doublecortin-positive (DCX+) immature neurons
with active neuronal populations defined by a unit recording technique in behaving
rats. We found significant anatomical association (within 100um) between DCX+
neurons and the recording sites of place cells which exhibit spatially-tuned spiking
corresponding to animal’s location (p-value is less than 0.005), while such relationship
did not exist for a different active population. We further examined whether this
association is because the generation of place-cell activity requires local DCX+
neurons. By eliminating immature neurons with a lentivirus-based method, we found
that place-cell activity is intact when local DCX+ neurons are ablated. Therefore,
although local DCX+ neurons are not required to generate intact place-cell activity,
anatomical association exists between immature neurons and place-cell activity. This
finding indicates the existence of an activity-dependent mechanism to create a
microenvironment fostering local recruitment of new neurons.
105
MEMORY AND MOTOR IMPAIRMENTS IN RATS OVEREXPRESSING ADENOSINE A2A
RECEPTORS IN THE FOREBRAIN
Valadas JS (1,2), Batalha VL (1,2), Comim CM (3), Shmidt, T (4), Sebastião AM (1,2),
Bader M (4) and Lopes, LV (1,2).
(1) Institute of Pharmacology and Neurosciences, Faculty of Medicine of Lisbon,
University of Lisbon, Portugal; (2) Unit of Neurosciences, Institute of Molecular
Medicine, University of Lisbon, Portugal; (3) Laboratory of Neurosciences and National
Institute for Translational Medicine, University of Southern Santa Catarina, Brazil; (4)
Max-Delbrück-Center for Molecular Medicine (MDC), Berlin, Germany
In brain, the major modulatory function of adenosine is carried by activation of A1 and
A2A receptors. A2A receptors are increased in hippocampus during ageing and upon
stress, two situations associated with memory impairments. Here we have
characterized a transgenic rat line overexpressing A2A receptors in forebrain. While A2A
receptors are increased in transgenic’s forebrain (cortex: 373±190%, hippocampus:
2226±727% and striatum: 134±17.3%, n=3), A1 receptors remained unchanged in the
hippocampus. Memory recall but not learning is reduced in transgenic rats, as assessed
in Morris Water Maze and Y-maze tests. Motor impairments were observed in
transgenic rats during rotarod experiments (latency to fall decreases to 13.6±0.065%,
n=10), but average speed and number of transitions were maintained between groups.
Transgenic rats displayed lower levels of anxiety in the elevated plus maze test (open
arms interval increases 215±25.3% in transgenic rats, n=9). Overall these results
support a causal effect of the increase of A2A receptor levels in memory impairments,
either in cortical and hippocampal dependent tasks. Motor deficits could be related to
A2A receptor modulation of striatal dopaminergic system. This transgenic line can be
further used to evaluate the impact of A2A overexpression on neuronal function,
excluding the peripheral side effects associated.
Funding: Fundação para a Ciência e Tecnologia
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MAPPING GLYCINE RECEPTOR AND TRANSPORTERS IN CULTURED RAT CORTICAL
ASTROCYTES
Valente CA, Aroeira RI, Ribeiro JA and Sebastião AM
Institute of Pharmacology and Neurosciences, Faculty of Medicine and Unit of
Neurosciences, Institute of Molecular Medicine, University of Lisbon, Portugal
Glycine-mediated neurotransmission, well established at the caudal regions of the
central nervous system, has been disregarded in the brain. In the brain, neuronal
glycine receptor (GlyR) is composed by subunits alpha (1-3) and beta, but little
information about glial GlyR is available. Glycine transporters (GlyT), which ensure
glycine removal from the synaptic cleft, are also essential elements of glycine-mediated
transmission hardly investigated in the brain. Given that glycinergic transmission is
considered a potential alternative therapeutic target for the treatment of epilepsy, it is
crucial to better understand its components in the brain, in both neuronal and glial
cells.
For this study, astrocytic cultures were prepared and analyzed at various
developmental stages. Western blot analysis confirmed GlyR expression and qPCR
detected alpha2 and beta subunit transcripts. Fluorescence immunocytochemistry
showed that GlyR was present in the cell body of GFAP+ cells and in some astrocytic
processes. qPCR also identified GlyT1 and GlyT2 transcripts. Fluorescence
immunolabelling confirmed GlyT1 and GlyT2 expression in astrocytes and revealed
developmental
changes
in
their
subcellular
localization.
This study confirms the presence of GlyR and GlyT in cortical astrocytes, both at mRNA
and protein levels. This knowledge is important to promote further investigation on the
functional meaning of glial GlyR and GlyT during both physiological and pathological
processes.
FUNCTIONAL INTERACTIONS BETWEEN GALANIN AND DOPAMINE RECEPTORS: ROLE
OF D-5 AND GAL-1 RECEPTOR ON ACETYLCHOLINE RELEASE AND SYNAPTIC
TRANSMISSION
Vaz SH (1,2), Ferré S (3), Franco R (4), Ribeiro JA (1,2), Sebastião AM (1,2)
(1) Institute of Pharmacology and Neuroscience, Faculty of Medicine, University of
Lisbon, Portugal; (2) Unit of Neurosciences, Institute of Molecular Medicine, University
of Lisbon, Portugal; (3) National Institute on Drug Abuse, IRP, NIH, DHHS, Baltimore,
US
The interest for galanin actions in the hippocampus has increased recently because of
neuroprotective actions of this peptide (Counts et al., 2008), together with reported
inhibitory actions of galanin upon synaptic plasticity and cognition (Badie-Mahdavi et
al., 2005). Galanin-catecholamine interactions within the hypothalamus and the
anteromedial frontal cortex of rat had been reported (Melander et al, 1987).
In the search of a possible functional interaction between dopamine and galanine
receptors in the hippocampus, we evaluated the influence of a D1/D5 agonist and of
galanin over acetylcholine (ACh) release and upon glutamatergic synaptic transmission.
Neither galanin nor the D1/D5 selective agonist, SKF 38393, affected the K+-induced
ACh release. However, pre-activation of D1/D5 receptors triggered an excitatory effect
of galanin on evoked ACh release. Galanin significantly inhibited (-21 ± 2.6%) fEPSP
slope. Remarkably, in presence of this D1/D5 agonist the galanin effect was converted
into an excitatory one, increasing the slope of fEPSPs by 15.4 ± 2.4%, an effect
prevented by the dopamine D1/D5 receptor antagonist, SCH 23390, as well as by the
muscarinic receptor antagonist, atropine. It is concluded that galanin and D1/D5
receptors cross-talk to modulate hippocampal excitability, and that this cross-talk
involves cholinergic inputs to glutamatergic neurons.
FEMALE SEXUAL BEHAVIOR: NEURONAL PATHWAYS FOR AROUSAL TERMINATION
Valente SS and Lima SQ
Champalimaud Neuroscience Programme, Lisbon, Portugal
Similar to other motivated behaviors, sexual arousal has a beginning and an end during
the normal flow of sexual behavior which is critically influenced by the central nervous
system. Although in males ejaculation leads to termination of arousal, in females this
process is much less clear.
SONIC HEDGEHOG (SHH) EXPRESSION BY MESENCEPHALIC DOPAMINE (DA)
NEURONS ACTS AS SENTINEL FOR CHOLINERGIC DYSFUNCTION AND REGULATES
CELL FATE DETERMINATION IN THE SUBVENTRICULAR ZONE (SVZ)
Verbitsky M (1), Perez M (2), Gonzalea-Reyes LE (3), Kottmann AH (1)
(1) Columbia Univ., New York, NY; (2) New York Univ., New York, NY; (3) Case
Western Univ., Cleveland, OH
Adaptation of cellular outcome of germinal niche activity to current physiological needs
requires the generation of cell type specific signals for tissue deterioration and a
mechanism by which these signals interfaces with cell fate determination. DA neurons
elaborate axonal projections to A and C cells of the SVZ. We demonstrate that DA
neurons express the morphogen Shh throughout adult life. We found that Shh
expression by DA neurons is up-regulated in graded manner correlated with the
severity of pharmacologically induced dysfunction in cholinergic neurons that are
synaptically connected with DA neurons. Ablation of Shh from DA neurons results in
the production of increased numbers of Pax6+ - and a concomitant reduction in the
numbers of Olig2+ - lineage precursor cells in the SVZ. The changes in relative
proportions of SVZ precursor populations translate into altered olfactory bulb cytoarchitecture and olfactory dysfunction. We reveal an extension of Spemann’s
“organizer” principle to sources of variable morphogenic activity that are in contact
with the SVZ through axonal projections. Thereby tissue corruption at a physical
distance can impinge on the qualitative outcome of germinal niche activity. Our results
provide a potential mechanism that could lead to olfactory dysfunction observed in
adult onset neurodegenerative diseases.
Our hypothesis is that female sexual arousal is controlled by a neuronal system that
integrates arousing sensory stimulation until an internal threshold is reached, ending
sexual drive and initiating a refractory period.
Using female mice as a model system, our first goal is to identify which brain areas
receive afferent sensory input from genital areas through a combination of transsynaptically anterograde and retrograde tracing experiments. Then, using a paced
mating paradigm we intend to characterize the normative sexual behavior leading to
arousal termination, allowing us to delineate frame points to check for IEG as readout
for neuronal activity, functionally characterizing where and how vagino-cervical
stimulation is specifically represented in the brain. Ultimately, the goal is to influence
female sexual behavior through neuronal manipulation taking advantage of
optogenetic methods, establishing a causal link between the activity of neuronal
circuits and the induction of sexual satiety, shedding new light into this fascinating and
fundamental female behavior.
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PRECISION IN MUSCULAR CONTROL: GAIN MODULATION IN SPINAL MOTONEURONS
BY SUB-THRESHOLD VM-FLUCTUATIONS.
M. Vestergaard, R.W. Berg
Dept. Neuroscience and Pharmacology, U. of Copenhagen, Copenhagen, Denmark
The mechanisms underlying the large dynamic range in motor systems are poorly
understood. We have previously shown that the intensity of synaptic inhibition and
excitation co-vary in phase (rather than out of phase) during rhythmic limb movements
(Berg et al. Science 2007). This could provide a mechanism for gain modulation in
motoneurons. Fluctuations in membrane potential due to balanced synaptic input is a
possible candidate for gain modulation in neurons, as suggested (Berg et al PLoS ONE
2008), but issues still remain: 1) is gain modulation by balanced synaptic fluctuations
in fact used by the nervous system to adjust the dynamical range? 2) does this
mechanism also adjust dynamical range and improve precision in motor systems?
Scratch spinal network activity in the turtle is an ideal model for addressing both
issues. Here we quantify the motor output during scratching and relate it to the
intensity of the synaptic fluctuations and the gain recorded in individual motoneurons.
We find that: 1) the FI-gain of individual motoneurons is modulated during motor
behavior. 2) Motor output (quantified as the integrated electroneurogram (ENG) of hip
flexor nerves) correlates with this gain. Interestingly, this relation represents a
functionally meaningful gain modulation because it scales the force precision with the
absolute force in analogy to Weber's law for sensory perception, i.e. deltaForce/Force
= constant. Gain is equivalent to deltaForce and the ENG is equivalent to Force. 3)
Gain is reversely related to the magnitude of the fluctuations in membrane potential (i.
e. sigma of Vm), as previously predicted from theory (see e. g. Tuckwell 1988).
DIFFERENT TYPES OF PUTAMEN ACTIVITY DURING MULTISENSORY OPERANT TASKS
Vicente AF (1), Bermudez MA (1), Romero MC (1), Perez R (1,2) and Gonzalez F (1,3)
(1) Department of Physiology. School of Medicine. University of Santiago de
Compostela, Santiago de Compostela, Spain; (2) Department of Ophthalmology,
Hospital da Barbanza, Ribeira, A Coruña, Spain; (3) Department of Ophthalmology,
University Hospital, Santiago de Compostela, Spain
Putamen is a nucleus from the basal ganglia traditionally related to movement
execution. However, some studies have shown its important role in sensory processing.
To further study its function, we trained two awake monkeys (Macaca mulatta) to
perform multisensory operant tasks by using videoclips as stimuli. Videoclips showed a
frontal view of a human face moving either up and down and saying ‘yes’, or laterally
and saying ‘no’. The animal had to press a lever during ‘yes’ trials to obtain a reward
and not to press the lever during ‘no’ trials. Videoclips involved only the image, only
the sound or both. We found neuronal activity during the different phases of the task.
Three neuron populations were described: visual-related neurons, movement-related
neurons, and reward-related neurons. We did not find auditory-related neurons. These
findings suggest that putamen is modulated by different events during the execution of
complex operant tasks.
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FAST TIME SCALE OF PHASE-OF-SPIKE CODING OF SOUNDS IN HIPPOCAMPAL
INTERNEURONS
Vinnik EM, Itskov PM
Scuola Internazionale Superiore di Studi Avanzati, now at Champalimaud Centre for the
Unknown
Oscillatory synchronization underlies communication between neurons within the same
network and between different cortical areas. It has been related to perception,
attention and awareness. Oscillations facilitate information transmission by reducing
noise and amplifying signals. It is often assumed that the preferred phase of firing is
fixed relative to the global rhythm and in itself does not carry information. However,
the preferred phase-of-firing can shift in individual cells, as has been shown in
hippocampal place cells. Encoding of sensory events in hippocampus is crucial for
episodic memory. How sensory events are encoded in the temporal patterns of spikes
was the question of our study. Rats performed 4 stimuli two-alternative forced choice
discrimination task, which allowed disentangling neural activity related to sounds and
place. Theta oscillation was prominent and many neurons in hippocampus phaselocked to the theta oscillation (~8 Hz). We found that preferred phase of neuronal
firing and phase-locking strength changed in the sound-specific manned. Interestingly,
phase-coding and firing rate coding could appear independently of each other: In 70%
of cases the phase of spike coding was present without any difference in the firing
rate. In interneurons spike timing relative to theta oscillation was most effectively
read-out on the short time scales (integration window shorter than 15 ms). The data
suggest that phase-of-firing coding is a general encoding mechanism, not limited to
spatial information. Stimulus-specific spike timing patterns, together with general
accuracy of neuronal phase-locking, might be important for hippocampus-mediated
associations of sounds and place.
CORTICAL THICKNESS ABNORMALITIES IN CHILDREN WITH NEUROFIBROMATOSIS
TYPE 1
Violante IV, Ribeiro MJ, Bernardino I, Duarte J, Silva E, Castelo-Branco M
IBILI, Faculty of Medicine, University of Coimbra, Portugal
Neurofibromatosis type 1 (NF1) is a common single gene disorder affecting the
nervous system with a high incidence of cognitive deficits, especially in attention,
executive function and visual-perception domains
Previous anatomical studies measuring grey matter volume in NF1 reported increases
or no differences in comparison with controls. This might reflect problems with brains
co-registration across subjects. Using cortex-based alignment it is possible to improve
cortical co-registration and accurately compare cortical thickness in vivo. Cortical
thickness (CT) analysis was used to provide more knowledge about cortical structure in
NF1.
We examined CT in 16 children with NF1 and 16 carefully matched controls (age range
7-16 years). We ensured that groups did not differ in mean age, gender, grey matter,
white matter, total intracranial volume, handedness and IQ.
Our results indicate that NF1 children have increased CT bilaterally in occipital and
parietal regions and also in left hemisphere temporal regions when compared to the
control group. Moreover, there was higher extension of abnormal CT in left than right
hemisphere.
The thicker cortical regions observed in NF1 children suggest abnormal maturation and
probable reduced “pruning” of synapses with consequently inefficient recruitment of
neural networks underlying functional abnormalities observed in NF1.
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INHIBITORY PLASTICITY BALANCES EXCITATION AND INHIBITION IN SENSORY
PROCESSING AND HEBBIAN ASSEMBLIES
Tim P Vogels, Henning Sprekeler, Friedemann Zenke, Claudia Clopath, Wulfram
Gerstner
École Polytechnique Fédérale de Lausanne (EPFL)
The balance of excitatory and inhibitory membrane currents recorded in neurons
during stimulated and spontaneously active network states has been the focus of many
recent experimental and theoretical studies. The function of such balance states has
been hypothesized to enable fast, stable and diverse network responses, to amplify the
response to certain stimuli, or to allow the establishment of functional network
architectures by means of dynamically controlling this balance in distinct groups of
cells. Despite the recent interest in these phenomena, no mechanism has been brought
forward that would allow the establishment of such balanced networks.
Using networks of integrate-and-fire neurons, we show that spike timing-dependent
inhibitory learning rules can succeed in establishing globally balanced networks.
Additionally, we show that in a feedforward architecture, the same learning rules
establish a detailed balance in each cell. As a result, cells with stimulus-tuned
excitatory input adjust their inhibitory synapses until inhibition and excitation have
similar stimulus tuning. This effect is largely independent of the absolute number of
synapses, the input correlation structure and the firing rate statistics of the input
signals. We conclude that inhibitory plasticity can establish stable network
configurations, in which perturbations (memories) in the excitatory tuning are quickly
and automatically balanced out by inhibitory plasticity. Given that the balance of
excitatory and inhibitory activity in the brain has recently emerged as a powerful
mechanism to govern neuronal dynamics, our results could be most helpful in
understanding how such balanced systems could establish and maintain themselves
naturally and without intelligent control mechanisms.
WEAK AND NON-DISCRIMINATIVE RESPONSES TO CONSPECIFICS IN THE RAT
HIPPOCAMPUS
Von Heimendahl M, Rao RP, Brecht M
Bernstein Center for Computational Neuroscience, Humboldt University of Berlin,
Germany
Little is known about how hippocampal neurons in rodents respond to and represent
conspecifics. To address this, we let rats interact while studying dorsal hippocampus
with extracellular recordings and immediate early gene (c-Fos) expression. In sessions
with multiple different stimulus rats, no cell responded differentially to individual rats.
We did find, however, that the presence of other rats induced a significant
enhancement or suppression of firing in a small fraction of neurons. As expected, many
neurons had place fields. The rat-induced modulations were not place-independent,
but linked to the spatial responses. While neurons did not discriminate between
individual rats, they did discriminate between rats and inanimate objects. Surprisingly,
neuronal responses were more strongly modulated by objects than by rats, even
though subjects spent more time near their conspecifics. The c-Fos data revealed
expression induced by social encounters in the amygdala, but - consistent with the
physiology data - not in the hippocampus. To our knowledge, this is the first report of
hippocampal responses during interactions with conspecifics. Social responses were
rare and lacked individual specificity, altogether speaking against a role of rodent
hippocampus in social memory.
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DISENTANGLING THE FUNCTIONAL CONSEQUENCES OF THE CONNECTIVITY
BETWEEN OPTIC-FLOW PROCESSING NEURONS
Weber F (1), Machens CK (2), and Borst A (1)
(1) MPI of Neurobiology, Germany; (2) Ecole Normale Superieure, France
Neurons in sensory areas are typically highly inter-connected. Coupling two neurons
can synchronize their activity and affect a variety of single cell properties as their
receptive field, firing rate, or gain. All these factors must be considered to understand
how two neurons should be coupled to optimally process stimuli. Here, we quantified
the functional impact of an inter-hemispheric interaction between two optic-flow
processing neurons in the fly (Vi and H1). Using a generative model, we estimated a
uni-directional coupling from H1 to Vi. We found that the coupling strength significantly
improves the information about the optic-flow in Vi. However, the coupling is still weak
enough such that Vi’s rotation tuning is left unaffected by inputs from H1. Further
analysis revealed that the strength and directionality of the interaction between Vi and
H1 improves the optic-flow encoding such that the information carried by a single spike
is maximized in each neuron.
ESTIMATING THE NUMBER OF NEURONS AND TEMPORAL SCALE IN
SOMATOSENSORY PERCEPTION
Wohrer A (1), Romo R (3) and Machens C (1,2)
(1) Department of Cognitive Studies, Ecole Normale Supérieure, Paris, France; (2)
Champalimaud Neuroscience Program, Champalimaud Center for the Unknown, Lisbon,
Portugal; (3) Institute of Cellular Physiology and Neuroscience, Universidad Nacional
Autonoma de Mexico
We propose and parametrize a neural population coding scheme, which relates neural
activities in the primary somatosensory cortex to tactile perception, in macaques
performing a two-stimulus discrimination task. The model assumes that the neural
population's spikes are integrated in time and across neurons to form a single readout
signal, which remains present "online" as long as the stimulation lasts. Being present
"online", this readout signal can be extracted at any time to form a percept. We
confront this model to experimental data consisting of: single-cell electrophysiology for
several hundreds of neurons, partial measures of pairwise noise correlations between
neurons, and psychometric indicators linked to the monkeys' behavioral decisions.
These data impose strong constraints on the parametrization of the proposed coding
scheme. In particular, it naturally yields estimates of the number of neurons
contributing to the monkeys' tactile percept, and of the typical scale of temporal
integration producing this percept.
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RECORDINGS AND OPTOGENETIC MANIPULATIONS OF DEFINED INTERNEURON
SUBTYPES IN FEAR CONDITIONING
Wolff SBE (1), Herry C (2), Ehrlich I (3), Tovote P (1), Ciocchi S (4), Letzkus JJ (1),
Mueller C (1), Luethi A (1)
(1) Friedrich Miescher Institute for Biomedical Research, Switzerland; (2) INSERM
U862, Neurocentre Magendie, France; (3) Hertie Institute for Clinical Brain Research,
Germany; (4) Center for Brain Research, Medical University Vienna, Austria
Classical fear conditioning is one of the most powerful models to study the neuronal
substrates of associative learning and the mechanisms of memory formation in the
mammalian brain. In unraveling the substrates of memory storage, the major focus
has been the study of excitatory elements of the brain. However, interneurons are
critical components of neuronal networks, shaping spatio-temporal patterns of network
activity. The role of amygdala interneurons in fear conditioning is poorly understood.
Using single unit recordings in behaving animals we identified putative fast-spiking
interneurons based on electrophysiological properties and inhibitory cross-correlations.
These recordings revealed functionally distinct classes of putative fast-spiking
interneurons. To unambiguously identify distinct subtypes of interneurons and to
determine causal relationships between interneuron activity and behavior, we
combined single unit recordings with a cell-type specific optogenetic approach.
Recordings from optogenetically identified PV+ interneurons during fear conditioning
showed differential activity during tone and foot-shock exposure. ChR2-mediated
activation of PV+ interneurons during the shock impaired fear learning, whereas
activation during the tone enhanced learning. Matching the activity of optogenetically
identified PV+ interneurons to our database of putative interneurons together with
additional optogenetic manipulations will clarify the role of PV+ interneurons in the
acquisition, extinction and retrieval of fear memories.
THE NEURAL BASIS OF SPATIAL REPRESENTATION OF 2-D AND 3-D ENVIRONMENTS
IN THE HIPPOCAMPUS AND ENTORHINAL CORTEX OF BATS
Michael M. Yartsev (1), Menno P. Witter (2) and Nachum Ulanovsky (1)
(1) Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel; (2)
Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory,
Norwegian University of Science and Technology, Trondheim, Norway.
We used a novel animal model - the Egyptian fruit bat, to study spatial representation
of 2D and 3D environments in the hippocampus & medial entorhinal cortex (MEC) of
mammals. Here, I will describe two projects:
(1) What are the underlying neural mechanisms giving rise to the grid formation?
Two competing classes of theoretical models are suggested: network models, based on
attractor dynamics versus oscillatory interference models, based on continuous thetaband oscillations. To date these models could not be dissociated experimentally,
because rodent grid-cells always co-exist with continuous theta oscillations. We
conducted the first electrophysiological recording from the MEC of freely crawling bats
and found that, grid cells existed in the absence of continuous theta oscillations and
theta modulation of spiking activity which causally argues against the oscillatory
interference models.
(2) How is three dimensional space represented in the neural activity of hippocampal
neurons?
Using a tetrode microdrive and a custom, lightweight multi-channel neural telemetry
system, we conducted the first electrophysiological recordings from the hippocampus
of freely flying mammals. Individual well-isolated single units were recorded from the
bat hippocampus during flight. These neurons had spatially-restricted place-fields that
represented all three dimensions, suggesting that all 3 dimensions are represented by
hippocampal neurons.
BRIDGING THE GAP: A DYNAMIC MODEL OF COMMON NEURAL MECHANISMS
UNDERLYING THE FRÖHLICH EFFECT, THE FASH-LAG EFFECT, AND THE
REPRESENTATIONAL MOMENTUM EFFECT
Wolfram Erlhagen (1) and Dirk Jancke (2)
(1) Department of Mathematics and Applications, University of Minho, Portugal, (2)
Institute for Neuroinformatics, Ruhr-University Bochum, Germany
In recent years, the study and interpretation of mislocalization phenomena observed
with moving objects have caused an intense debate about the processing mechanisms
underlying the encoding of position. We use a neurophysiologically plausible recurrent
network model to explain visual illusions that occur at the start, midposition, and end
of motion trajectories known as the Fröhlich, the fash-lag, and the representational
momentum effect, respectively. The model implements the idea that trajectories are
internally represented by a traveling activity wave in position space, which is
essentially shaped by local feedback loops within pools of neurons. We first use
experimentally observed trajectory representations in the primary visual cortex of cat
to adjust the spatial ranges of lateral interactions in the model. We then show that the
readout of the activity profile at adequate points in time during the build-up, midphase,
and decay of the wave qualitatively and quantitatively explain the known dependence
of the mislocalization errors on stimulus attributes such as contrast and speed. We
conclude that cooperative mechanisms within the network may be responsible for the
three illusions, with a possible intervention of top-down influences that modulate the
efficacy of the lateral interactions.
MOTOR POOL POSITION AND TARGET TOPOGRAPHY REGULATED BY BETA- AND
GAMMA-CATENIN ACTIVITIES
Zampieri N, Demireva EY, Shapiro L and Jessell TM
Howard Hughes Medical Institute, Depts. of Neuroscience, and Biochemistry and
Molecular Biophysics, Columbia University, New York,NY, USA
In the spinal cord the organization of motor neurons into discrete pools is spatially
linked to the location of their muscle targets, establishing a topographic map. To
define the significance of motor pool organization for neuromuscular map formation we
assessed the role of cadherin-catenin signaling in motor neuron positioning and limb
muscle innervation. We find that beta- and gamma-catenin control motor neuron
positioning but have no impact on axonal growth and target specificity in the limb,
preserving the link between motor neuron transcriptional identity and muscle
innervation. Inactivation of N-cadherin similarly affects pool positioning, albeit with
reduced penetrance. These findings show that cadherin-catenin signaling directs
intraspinal programs of motor neuron organization and imposes topographic order on
an underlying identity-based neural map.
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FEMALE SOCIAL PREFERENCE IN MICE DEPENDS ON MALE QUALITY AND FEMALE
EARLY EXPERIENCE
Zinck L and Lima SQ
Champalimaud Neuroscience Programme, Lisbon, Portugal
Mate choice is a key driving force of evolution but the proximate mechanisms allowing
mate assessment by the nervous system are still unknown. In order to understand how
mate value and preferences are represented in the brain, we have established a
behavioral paradigm where the subjective value of prospective mates can be
manipulated. Our behavioral paradigm takes advantage of a natural situation occurring
in Europe where two subspecies of mouse, Mus musculus musculus and M. m.
domesticus, form a narrow hybrid zone, and show asymmetric mate choice. By using
inbred strains of mice we were able to translate this situation into laboratory conditions
and to control female preference in a reproducible way. In particular, M. m. musculus
females exhibit a strong homosubspecific preference, as the one found in nature, that
is stable over time and reproducible across individuals (n = 54). However if females
are fostered in a domesticus environment they show a reversed preference (n = 16).
This situation therefore allows us to compare the neuronal representation of the same
stimulus male which has a different value, depending on the female's early experience.
We are currently taking the first steps to explore which brain regions might underlie
this behavioral preference.
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