Why adult neuropsychological models don’t
work for neurodevelopmental disorders
Annette Karmiloff-Smith
Birkbeck Centre for Brain & Cognitive Development
University of London
BPS Stratford talk, January 2012
1
Plan of talk
1.
Are NDDs caused by domain-general or domain-specific
deficits? A third alternative: domain-relevant deficits that
become domain-specific over developmental time
2. Example of neuroconstructivist approach: Domain-specific vs
domain-relevant approaches to cross-syndrome comparisons:
the case of infant sensitivity to number: DS/WS
3. Differentiate static vs dynamic approaches to
neurodevelopmental disorders
Domain-general approaches
e.g.
Piaget’s 3 domain-general processes:
assimilation/accommodation/equilibration
e.g. Production systems:
single domain-general Problem Solver
(e.g. SOAR)
Domain-general approaches have difficulty explaining
uneven cognitive profiles
3
Domain-specific approaches
Neuropsychological patients
(e.g. dyscalculia, agrammatism)
Developed brains damaged in
their mature endstate
Children with genetic disorders
and seemingly pure dissociations
(e.g. developmental dyscalculia/G-SLI)
number
social
MotceVocabul
Social
processingary Face
cognitio
processing
n
Grammar
Number
Vocabulary
Cognition
Face
Processing
number
Face
processing
Social
cognition
Number
Developing brains….
Motion
processing
Grammar Face
Processing
4
Problem with adult neuropsychology approaches:
ignore developmental history of the organism
“Williams syndrome can be explained in terms of selective deficits to an otherwise
normal modular system”(Clahsen & Temple, 2003, p.26)
Adult neuropsychological model of juxtaposition
of impaired/intact modules =
inappropriate for developmental syndromes
Domain-specificity: may be outcome of development,
not necessarily its starting point
Not built-in modules, but gradual process of modularization
(progressive neural specialisation and localisation)
over developmental time
5
If not built-in domain-specific modules,
only alternative = domain-general processes?
3rd alternative = domain-relevant processes:
-include biological constraints (small differences in neuronal type,
neuronal density, firing thresholds etc.)
- take account of cross-domain interactions over time
- more dynamic developmental view than d-s accounts
Initially both hemispheres compete to compute inputs.
Circuits most domain-relevant win out and become
specialised over developmental time
6
Seek domain-relevant deficits early in
developmental trajectory
Example of domain-specific
versus domain-relevant approach
from cross-syndrome comparison
of Down and Williams syndromes
7
Down syndrome/Williams syndrome
Down syndrome:
trisomy on chromosome 21
all genes normal, but 3 instead
of 2 copies of each gene
> too much gene expression
Williams syndrome: 28 genes missing on one copy of
chomosome 7
< too little gene expression
8
Down syndrome/Williams syndrome
The cognitive end state DS > WS
Adolescents and adults:
Butterworth Battery:
TD > DS > WS
Far = faster
SDE, addition/subtraction,
number facts etc.
Children:
Close = slower
WS = DS = TD
Counting:
but 1,2,3……4….5,6,7,8,9,10
Understanding cardinality:
TD > WS (very poor)
DS = study in progress
Spatial MA predicts cardinality in TD
Verbal MA predicts cardinality in WS -> different developmental trajectories
Ansari & KK-S, 2002; Paterson Girelli, Butterworth & KK-S, 2003
Down syndrome/Williams syndrome
The cognitive start state
Infant sensitivity to number
in Down syndrome and Williams syndrome
both with deficits in visual attention
10
Interpreting data in terms of
domain-specificity or domain-relevance
Infant sensitivity to number
Under the domain-specific interpretation:
a double dissociation between
Down syndrome & Williams syndrome
Double dissociation:
one group:
fine on A, impaired on B
other group:
fine on B, impaired on A
-> based on adult neuropsychological findings and
implies separate neural and cognitive processes
11
Small number discrimination
in WS & DS infants
Exact small number (2 vs 3):
TD infants OK @ 3-4 months
WS/DS tested @ 10-40 months
WS=OK DS=very impaired
Replicated with second set of infants
with dot arrays
DS < WS = TD
(Paterson, Girelli, Butterworth & Karmiloff-Smith, 2003; Van Herwegen, Ansari, Xu & Karmiloff-Smith, 2008)
23
Large number discrimination
in WS & DS infants
Approximate large number (magnitude)
TD infants OK @ 6-7 months ratio 1:2
WS/DS tested @ 10-40 months 8 vs 16
(ratio 1:2)
DS=OK; WS=impaired
WS < DS = TD
(Paterson, Brown, Johnson & Karmiloff-Smith, 1998; Van Herwegen, Ansari, Xu & Karmiloff-Smith, 2008;
Karmiloff-Smith, d’Souza, Dekker, van Herwegen, Radic, Xu & Ansari, submitted)
24
Double dissociation: WS/DS infants
Williams syndrome: Small exact number: intact
Large approx number: impaired
Down syndrome:
Small exact number: impaired
Large approx number: intact
25
Everything seems very clear…
Double dissociation across syndromes
Two separable numerical sub-systems
Innately specified
Genetically determined
WS:
One or more of the 28 deleted genes on chromosome 7 contribute to
domain-specific deficit in approximate number system
and spare exact number system
DS:
One or more of the extra genes on chromosome 21 contribute to
domain-specific deficit in exact number system
and spare approximate number system
26
Everything seems very clear…
But….
“double dissociation/spared/intact” =>
adult neuropsychological models of mature brain: static
Not appropriate for neurodevelopmental syndromes: dynamic
Infant brain:
specialisation and localisation of function = progressive.
In early development, not dissociated modules,
but cross-domain interactions
Must trace domain-specific, cognitive-level number deficits
back to origins in basic-level, domain-relevant processes
27
How do WS and DS infants scan the
numerical arrays?
Maybe DS/WS differences for number = not specific to
number but due to differences in
visual attention/visual scanning patterns
several experiments on visual saccade planning
WS = very impaired – serious visual disengagement problems
DS = proficient like TD - but serious sustained attention problems
Hypothesis:
Scanning large arrays-> brain focuses on
global quantities = DS
Scanning small arrays-> brain fixates on
individual objects = WS
28
DS infant:
WS infant:
focus on quantities
focus on individual objects
29
WS infants very impaired in planning
basic eye-movement saccades
Basic-level deficit in visual saccade planning
early in WS trajectory
deficits in discriminating large number
Next important question:
Is this deficit domain-relevant to other
developing domains?
30
Single dissociation between
number and face processing within WS
Different labs worldwide:
WS face processing: ‘in the normal range’
on standardised tasks (Benton, Rivermead)
number: impaired
face processing: proficient
face
processing
on standstandardised
tasks
number
31
Domain-specific “intact” face processing
module in WS?
Could visual saccade planning deficit
be domain-relevant to both number and face processing,
i.e. deficit explains both impaired and proficient
performance?
Numerous experiments:
WS: featural analysis of faces (fixated)
TD: configural analysis of faces (rapid)
What about WS brain?
32
WS neural signatures
for face and car processing
WS adolescent in
Geodesic HD-ERP net
Grice, deHaan, Halit, Johnson, Csibra, & Karmiloff-Smith, 2003
33
WS: no progressive modularization
despite good behavioural scores
Controls
Healthy controls:
Progressive processing restriction of input type
WS
WS: failure to localise
WS
Healthy controls:
Controls
Progressive restriction brain circuit
34
Proficient face processing in WS
Good behavioural scores sustained by:
different cognitive processes (featural)
different neural processes (lack of specialisation)
How to explain WS proficient face processing?
Due to enlarged Fusiform Face Area??
35
Vital to distinguish:
“developed” brain vs “developing” brain
FFA in WS adult brain is unusually large (in proportion to other regions):
2 interpretations (requiring developmental approach):
- large
FFA causes unusual face processing proficiences in WS
brain
behaviour
- unusual focus on faces influences enlargement of FFA over
developmental time :
brain
behaviour
Heightened auditory processing in utero => Focus on mother’s speech =>
Speech contingent with mother’s face at birth + Problems with visual
disengagement => WS fascination with faces >> FFA
36
WS: early basic-level deficits in saccade planning domain-relevant to several cognitive-level outcomes
attentional disengagement problems (DS sustained)
focus on local spatial features (DS on global)
featural processing of faces (DS global)
poor triadic attention -> delayed vocabulary
poor large number (DS opposite pattern)
good small number (DS opposite pattern)
Cascading developmental effects over time across several
emerging higher-level cognitive systems
37
Implications for intervention of
domain-relevant approach
- Should be syndrome-specific from basic research
- Should start in early infancy
e.g. WS: before e.g. number or face processing strategies emerge
- Not necessarily in domain of deficit
e.g. don’t train number: WS: train infant saccadic eye movements
DS: train infant sustained attention
- Possible cascading effects over developmental time
on several domain-specific outcomes
38
Static versus dynamic, developmental
questions
Static questions
Which modules are impaired and which are intact?
Where located in brain?
How are syndromes dissociated?
Dynamic questions
Is there a developmental explanation?
How do neural circuits change over time?
Which domains interact across their developmental trajectories?
How are syndromes dissociated and associated?
39
Static, non-developmental approach
Static focus on end-product (adult neuropsychology models:
“Williams syndrome can be explained in terms of selective
deficits to an otherwise normal modular system”
(Clahsen & Temple, 2003)
“Autism is due to a deficit in an innately-specified module
that handles theory-of-mind computations only”
(Leslie, 1992)
40
Dynamic, developmental approach
Dynamic focus on process of development:
“…brain volume, brain anatomy, brain chemistry, hemispheric asymmetry, and
the temporal patterns of brain activity are all atypical in people with WS. How could the
resulting system be described as a normal brain with parts intact and parts impaired, as the
popular view holds? Rather, the brains of infants with WS develop differently from the
outset, with subtle, widespread repercussions…”
(Karmiloff-Smith, 1998)
“... examine the crucial role of unbalanced excitatory-inhibitory networks…
leading to ASD through altered neuronal morphology, synaptogenesis and cell
migration”
(Persico & Bourgeron, 2006)
“ASD may involve premature pruning of synaptic connections early in
development”
(Thomas, Knowland, and Karmiloff-Smith, 2011)
41
Domain-relevant, Neuroconstructivist
approach causes researcher:
- ask different kinds of questions
- predict less obvious deficits elsewhere in system
- investigate cross-domain interactions over time
- trace cognitive-level deficits in childhood back to
basic-level deficits in infancy
- think more dynamically / developmentally
Dr Emily
Farran,
Institute of
Education
43
Dr Emily
Farran,
Institute of
Education
Niamh Willoughby-Farran
31st December, 2011 @ 6.26 a.m.
Weighing 8lbs.4oz
Farran & K-S
20th December, 2011 @ 9.00 a.m.
Weighing 1lbs.15oz
44
Gaia Scerif
Thierry Nazzi
Dagmara
Jo van
Herwegen
Annaz
Daniel
DanielAnsari
Ansari
Kate Humphries
Emily Farran
Thank you!
Joint work mentioned in talk
with past and current
Collaborators/Postdocs/Students
Julia Grant
Rick Gilmore
Sarah Paterson
Sarah Grice
Funding
Mayada
Francesca
Elsabbagh
Happé
Michael Thomas
Mark
Mark Johnson
Johnson
Rhonda Booth
Janice Brown
Fei Xu
Michelle
de Haan
Tessa Dekker
Dean D’Souza &
Monica Connolly
Kim Cornish
Maja Radic