1 Charles A. Nelson III Children s Hospital Boston/Harvard Medical School Harvard Center on the Developing Child Presented at NICHD Cognition Workshop, March 2011, Bethesda, MD
2 Outline I. Declaration of Bias II. Brain Development III. Typical and atypical cognitive development
3 I. A Declaration of Bias Study of typical and atypical cognitive development should co-exist Study of typical development essential to establishment of road map Study of atypical development essential for obvious reasons but also because such study may shed light on typical development
4 A Declaration of Bias (Con t) Cognitive development does not exist in isolation from development in other domains (e.g., social, emotional, language) The study of cognitive development should not be brainless imperative to ground such study in knowledge of the brain As appropriate, and within limits of experimental design and methods, study of cognitive development should also be informed by genetics
5 A Declaration of Bias (Con t) It is generally unhelpful and often biologically naïve to ascribe the term innate to cognitive development There should be an attempt to adopt a true developmental framework.moving on
6 II. Brain Development The Brain is the organ that drives cognitive development and is responsible for deviations in typical development Next slide
7 15 1/2 wks 22 weeks 23 weeks ~25 weeks 27 weeks Full term brain Adult
8 Correspondence between Brain and Cognitive Development
9 III. Select Domains of Cognitive Development Speech, Language, Reading Face processing Object concept Numerical Competence Memory Attention Theory of Mind Conceptual development Executive functions/cognitive Control/Functions subserved by the PFC Reasoning, planning, problem solving, working memory, inhibitory control, future-oriented behavior, cognitive flexibility etc.
10 A. Reading builds on speech and language Ability to co-localize sounds and sights (e.g., letters) Typically begins to emerge late preschool and is fully on line by age 8-9
11 11 Reading development Sound and Language Processing Phonological Processing/ Letter recognition Graphemephoneme Mapping Single word/ Connected text reading Lexical Access/ Comprehension/ Fluency
12 12 Reading is learned through explicit training, and many factors contribute to its successful acquisition and development Skilled readers utilize three main brain networks for decoding text: Anterior System Posterior dorsal System Posterior ventral System Modified after Pugh et al., 2001
13 Deviations in Speech, Language and Reading Pure speech delays and disorders Phonological difficulties, verbal dyspraxia Language delays and disorders Specific language impairment Autism Developmental Dyslexia
14 B. Face Processing Comes on-line within first weeks of life, but develops gradually over first year (due to built in constrains on visual development), with continued elaboration through Visual Development: Acuity adolescence 3 weeks Infant color sensitivity and acuity increase during the first year. 6 weeks 3 months 6 months
15 Face Processing (Con t) Newborns have rudimentary knowledge of faces By 3-4 months, have concept of faces Between 4-7 months, processing of facial emotion begins to accelerate rapidly Similar to speech perception, face processing undergoes perceptual narrowing with development, such that expertise develops gradually (next slide)
16 Pascalis, de Haan, & Nelson, Proportion of Looking Familiar Novel Proportion of Looking Familiar Novel 0 6-month 9-month Adult 0 6-month 9-month Adult * Pascalis, O., de Haan, M., & Nelson, C.A. (2002). Science, 296,
17 Face Processing, Con t Building blocks of face processing established in infancy but Recognition of identity, age, gender, and race continues to be refined through childhood These changes driven by specialization of cortical circuits in inferior temporal lobe (e.g., fusiform) Recognition of emotion (essential for social communication) also established in childhood, although ability to process fear continues to develop into adolescence These changes driven by amygdala and OFC
18 Deviations in Face Processing Autism Prosopagnosia common manifestation adulthood but developmental variant typically observed in childhood and adolescence Children experiencing early neglect or abuse Schizophrenia Adolescence/young adulthood Bipolar Late childhood/adolescence
19 C. Memory Two types Declarative (explicit) Non-declarative Declarative memory subserved by structures in the medial temporal lobe; Non-declarative subserved by nontemporal lobe structures (e.g., striatum)
20 Typical development of declarative memory functions birth Young adulthood Recognition memory Relational memory Flexibility Episodic per se Memory functions Improvement
21 Recognition memory An early emerging memory function, already present in 3-4-day old infants impacted after hippocampal lesion but more severe after perirhinal lesion.
22 Relational memory Seems to emerge later than recognition memory during postnatal development between 6 and 12-month-old, as assessed by a deferred imitation task present at 9 months of age, as assessed by a VPC task impacted by hippocampal lesion in adult individuals
23 Flexibility Relational memory evolves during the first two years of life to become more elaborate with age. extremely specific to the context in which learning occurs and gradually becomes more and more flexible flexibility is a fundamental component of relational memory, which is thought to depend on the integrity of the hippocampal formation
24 Episodic memory per se Emerge around 3-5 years of age most adults are unable to recall events that happened before this age, a phenomenon called infantile amnesia Dependent on the integrity of the hippocampal formation A key role for the dentate gyrus, and postnatal neurogenesis in DG continues through mid-life
25 Memory improvement Development of other cognitive function impact memory, leading to additional qualitative changes in the different memory functions subsequent to their emergence Memory functions continue to improve between 4 and 6 years of age and even until young adulthood (although by 9-10 years, memory quite good) PFC is implicated in episodic memory in adults and seems to be involved in the cognitive control of memory and specifically in the formation of detailed representations of experiences
26 Summary Early emergence of recognition memory might be subserved by early maturing circuits in perirhinal and hippocampal formation Gradual emergence of episodic functions subserve by the gradual maturation of the hippocampal formation (including dentate gyrus) Gradual maturation of existing episodic memory functions subserve by the protracted maturation of the frontal lobe.
27 Atypical Memory Development Learning disabilities Pure memory disorder (e.g., developmental amnesia ), such as children who experienced hypoxic-ischemic injury at birth, or children born to diabetic mothers Both typically emerge preschool and later But sensitive assays may be able to detect in infancy
28 28 Numerical development Tracking and comparing quantities (e.g., 8 vs. 16 sounds) Counting; One-to-one correspondence; Cardinality (i.e., that each count word refers to an exact quantity) Manipulating numbers (e.g., addition and subtraction); Fractions; Negative numbers Algebra, geometry, calculus, and beyond
29 Neural basis of numerical competence A meta-analysis of fmri studies of number processing points to parietal activation in adults Dehaene et al., 2003 Recent infant work also points to parietal regions responding to changes in quantity using near-infrared spectroscopy (NIRS)
30 Deficits in numerical competence Dyscalculia As prevalent as dyslexia Frequent in preterm infants despite normal IQ and reading scores reduced gray matter in IPS Numerical deficits and genetic disorders (e.g. Williams syndrome, Fragile X, Turner syndrome) Reduced activation in IPS in these populations Isaacs et al., 2001 Molko et al., 2003
31 Executive Functions Typically taken to include a collection of functions subserved disproportionately by the prefrontal cortex; includes Working memory Inhibitory control Planning/sequencing Resulting in: Future-oriented behavior Reasoning Problem solving
32 32 Executive Function Development rudiments of working memory Emerging inhibitory control and working memory Inhibitory control increases and working memory span; increases Emerging Cognitive Flexibility Continued development within EF domains and integration of these abilities to do long term / complex planning behavior
33 What Drives development of EFs? Assumption has been that pruning of synapses in PFC, which continues through late adolescence, coupled with changes in myelination (same time frame), make possible changes in EFs Presumably experience is what drives these changes although both genetic factors and experiential factors can undermine development of PFC and EFs (examples next slide)
34 Experiential factors to deviations in EFs Early Psychosocial Deprivation Children experiencing early institutionalization experience long-term deficits in executive functions (cf. Bucharest Early Intervention Project) and correspondingly, problems regulating attention Enhancement Several studies have identified computerized and classroom training programs that improve working memory in children (see work by Neville, Diamond, among others)
35 Non Experiential Factors Executive functions have strong heritability estimates in behavior genetics studies Disorders of executive functioning (ADHD) are among the most heritable and variation in genes that code for dopamine function have been identified as different in these disorders.
36 Developmental Time frame for emergence and elaboration of EFs Not surprisingly, given neural architecture, Efs have long developmental trajectory Although see rudiments of working memory in infancy, this develops most through preschool and elementary school In contrast, inhibitory control isn t clearly present till preschool and continues well through adolelence Planning and cognitive flexibility develop most through middle childhood and continue through late adolescence.
37 Behaviors affected by poor executive functions Learning disabilities (e.g., planning, problem solving) Externalizing disorders ADHD Conduct disorder Disruptive behavior disorder
38 The Future Understand how genes and experience contribute singly or interactively to drive changes in cognitive development Identification of sensitive periods in acquisition of cognitive skills Development of methods of early identification of children at risk for developing x,y,z disorder Improved methods for studying these functions from infancy through childhood (next slide)
39 The Future (con t) Develop/refine tools that permit one to examine neural mechanisms underlying changes in cognitive development. Recording Brain Activity from 128 electrodes (from children)