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What Neurodevelopmental Disorders Can Reveal about Cognitive Architecture Helen Tager-Flusberg Boston University.

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Presentation on theme: "What Neurodevelopmental Disorders Can Reveal about Cognitive Architecture Helen Tager-Flusberg Boston University."— Presentation transcript:

1 What Neurodevelopmental Disorders Can Reveal about Cognitive Architecture Helen Tager-Flusberg Boston University

2 Outline Discussion of whether neurodevelopmental disorders has potential to inform debates about cognitive architecture (methodological issues and complications) Example of research on theory on mind in NDD: autism and Williams syndrome Reinterpretation of the classical evidence

3 Defining Neurodevelopmental Disorders (NDD) Focus on genetically-based NDD NDD divide into gene/chromosome disorders (e.g., Down, Turner, Williams, PKU) and polygenic/complex disorders (e.g., autism, SLI) Genetic abnormalities (absence, mutation) disrupt normal development of brain Lead to different ‘phenotypes’ that are syndrome specific

4 Role of Disorders in Cognitive Science Lengthy tradition of using data from people with brain/cognitive damage to inform cognitive theory, and organization of cognitive system Examples from aphasia, amnesia, agnosia etc. A for Acquired disorders - provides rich information about dissociations between cognitive modules from the “end state”

5 Can Individuals with Abnormal Brain DEVELOPMENT Inform Cognitive Science? Disruption in brain development affects the ACQUISITION of cognitive systems Studies thus provide data on developmental processes; can study end state of this developmental process in adults with NDD Controversial whether NDD can provide evidence about cognitive architecture, even from a developmental perspective

6 Arguments Against: Karmiloff- Smith (1998) Because brains develop DIFFERENTLY in NDD –But little evidence for major differences in developmental processes –Not a logical argument against using NDD evidence

7 Arguments Against (contd 2) NDD does not create localized lesion; no simple intact/impaired cortical circuits that map directly onto cognitive modules –May be true for some disorders but not others –Depend on the NDD, the cognitive system, the individual

8 Arguments Against (contd 3) Developmental changes in the phenotype lead to fundamentally different organization; plasiticity in structure /function –Data on phenotypic changes from infancy are controversial and suspect –Plasticity is highly constrained; the brain is not a blank slate!

9 Alternative View - Arguments proposed by K-S not compelling. May depend on which NDD investigate Striking difference in children with different NDD - and subgroups within syndromes Depends on which cognitive module Identifying specific cognitive module that has been disrupted in NDD has been elusive

10 Methodological Issues in Studying NDD Heterogeneity in expression of phenotype within each syndrome –Individual differences related to genetic variation related to NDD –Individual differences related to genetic variation NOT related to NDD Differences related to experience –Age effects –Remediation/Compensation

11 Effects of Retardation and Language Limitations Task performance will be a function of –MR (g - cognitive efficiency?) - non-modular influences –Language (comprehend instructions; task content) These effects will potentially obsure syndrome-specific effects on cognitive module At the least, include subjects in limited age range, measures of IQ and language ability

12 Example: Theory of Mind (ToM) Since ToM entered the cognitive ‘cannon’ evidence from NDD has been central in arguments about its organization, modularity and innateness Classic studies of autism; more recent studies of other syndromes e.g., Williams

13 ToM in Autism Baron-Cohen, Leslie & Frith (1985) demonstrated failure on FB Many studies replicate their findings on FB and other related tasks; compared to control subjects and control tasks Support for view of selective impairment to ToM in autism Taken as evidence that ToM in unitary module under genetic influence with unique neurobiological substrate

14 Significance of ToM Hypothesis of Autism Provides a unified explanation for core social and communication symptoms in terms of an underlying cognitive module Selectivity of cognitive deficit identifies the specificity of impaired cognitive module Conforms with what is known about neurobiological substrate

15 ToM in Williams Syndrome Contiguous gene deletion (~25-30 genes on 7q11.32) Constellation of physiological, cranio-facial and cognitive profile (including MR) forming a unique phenotype Unusual interest in people, sociable, good language and face recognition Suggests spared ToM Karmiloff-Smith et al (1995) offer supporting evidence

16 ToM in NDD Claim for double dissociation in ToM Autism: impaired ToM module Williams: spared ToM module

17 Problems with this Classic Picture Criticisms of ToM hypothesis of autism Problems with the evidence of impairment in autism and sparing in WMS –Methodological issues Role of language and MR Question the basic view that ToM is directly and selectively affected by NDD

18 Criticisms of ToM Hypothesis of Autism ToM deficits are secondary to other domain general deficits such as “executive functions” Cannot explain full range of symptoms in autism Symptoms of autism predate ToM Children with other NDD (e.g., Down syndrome SLI) also fail ToM tasks

19 Problems with the Evidence Some children with autism PASS ToM tasks (e.g., 20% in Baron-Cohen et al., 1985; much higher in our studies) Our studies on ToM in young children (age 4-8) with Williams syndrome show that they are NO BETTER (or worse) on FB and related metarepresentational tasks than control children matched on age, IQ, and language

20 Reconciling the Evidence Performance on FB strongly related to language level (not nonverbal IQ) in broad range of children with NDD (and normal children) Computing the contents of propositional attitudes (e.g., beliefs) measures a representational capacity that can be acquired by language

21 ToM in Autism Fundamental impairments in the core module that computes information about mental states directly from perceptual inputs (e.g., face, voice, gesture) Impaired in knowledge of concepts of mental states IF have linguistic knowledge, then can access metarepresentational level using this alternative route

22 ToM in Williams Syndrome Fundamental sparing in the core module that computes information about mental states directly from perceptual inputs (e.g., face, voice, gesture) ? Relative sparing of knowledge of concepts of mental states MR decreases cognitive efficiency therefore, metarepresentational level also depends on support from language, and therefore not spared compared to controls

23 Language and FB Role of sentential/tensed complements in the acquisition of FB Communication verbs - say, tell, whisper Cognition verbs - think, know, forget –John said that he went shopping –Mary thought that John was sleeping –Larry believed that John was working John went to the movies!

24 Complements and ToM Parallels between sentential complements and the representational requirements for the contents of mental states (propositional attitudes) Can mark embedded clause true/false Semantic parallels between mental state and communication verbs and ToM (Pinker & Bloom, 1990 - evolutionary link)

25 Evidence for Links between FB and Sentential Complements Jill de Villiers et al. (1998) - longitudinal study of preschoolers: complements acquired prior to passing FB tasks Hale & Tager-Flusberg - training study: training on complements (communication verbs) led to changes on FB task Deaf children fail FB tasks - related to language ability especially complements (Peter de Villiers et al.)

26 Sentential Complements and ToM in Autism Battery of ToM tasks (FB Smarties, FB Sally-Anne, Perception/Knowledge) Extraction of say and think false complements General language measure (PPVT+EVT) Executive functions (spatial and verbal WM, WM+IC - stroop; planning: Tower) Annual Visits - Year 1 and Year 2

27 Subjects at Time 1 ~40 children aged 5-14, all diagnosed with autism using ADI and ADOS (Mean 8;3) IQ assessed using the Differential Ability Scales –VIQ Mean=82 sd=19 –NVIQ Mean=88 sd 21 PPVT Mean=84 sd=20 EVT Mean=79 sd = 19

28 Time 1 Variables Correlating with Time 2 ToM Age and general language partialled out –T1 Towerr=.51* –T1 Say complementsr=.56* –T1 ToMr=.62*** –NB: NOT Think complements or any other EF measures

29 What Predicts ToM at Time 2 Hierarchical regression analysis Step 1 - force in age, vocabulary and T1 ToM –R 2 =.65*** Step in the predictor variables (Say complements and Tower) according to significance level –Say complements: R 2 =.11** –Tower: R 2 =.01 ns

30 Summary of Autism Findings Ability to interpret sentential complements FOR COMMUNICATION VERBS predicted later ToM ability EF not related to ToM (so ToM isn’t secondary to EF, as claimed) ToM at T1 does NOT predict EF or sentential complements at T2

31 Implications Only linguistic knowledge for communication verbs predicts passing FB in autistic children Communication verbs do not entail conceptual understanding of mental states Passing FB does not entail ability to compute mental state information from faces/voices (evidence from Baron-Cohen, Klin, Meyer & TF) Language is an alternative bootstrap into ToM

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