Newborn THE EFFECTS OF EARLY FOCAL BRAIN INJURY

Newborn THE EFFECTS OF EARLY FOCAL BRAIN INJURY ON LANGUAGE AND COGNITION: Plasticity and Development Adult Brodmann, 1909

Key Issue: Link between Behaviors their Neural Substrate (i. e. , language production Broca’s area) How do associations between behaviors and the brain structures (that control them) emerge?

Laterality How do Cognitive skills become lateralized? (i. e. , Language Left Hemisphere) Early in life cognitive functions are bilateral (Infants and young children use different neural networks for language compared to adults)

Change across development: PLASTICITY Plasticity refers to the capacity for change Term widely used within neurosciences, refers to changes at all levels of the cognitive-neural system from neurochemistry to behavior.

Plasticity is fundamental for brain development 1. Brain development is DYNAMIC -Continuously changing (i. e. , new synaptic connections, new memory…) 2. Change requires INTERACTION -Intrinsic factors (Nature: gene expression) -Extrinsic factors (Nurture: environment, experience, learning)

Complexity of Nature X Nurture Interaction Difficult to link changes in complex behaviors to the corresponding neural changes - Animal models: i. e. , sensory deprivation studies, neural pathway alteration studies - Studies on Human Patient Populations: i. e. , Congenital Deaf, Stroke Patients…

Children with Perinatal Focal Brain Injury 1. Single, unilateral focal lesion (mostly from strokes) 2. Normal or corrected to normal vision / audition. 3. IQ within normal range From Moses, 1999

HOW DOES VERY EARLY FOCAL BRAIN INJURY AFFECT LANGUAGE ACQUISITION?

PRIMARY LANGUAGE AREAS IN ADULTS ARE IN THE LEFT HEMISPHERE RIGHT HEMISPHERE BROCA’S AREA: PRODUCTION OF LANGUAGE LEFT HEMISPHERE WERNIKE’S AREA: COMPREHENSION OF LANGUAGE

LEFT HEMISPHERE – ADULT Vocabulary Production in Children with Early Injury PRODUCTION LEFT HEMISPHERE COMPREHENSION LEFT POSTERIOR TEMPORAL LESIONS VOCABULARY PRODUCTION DEFICITS. LPT LESION

LEFT HEMISPHERE – ADULT Vocabulary Comprehension in Children with Early Injury PRODUCTION LEFT HEMISPHERE COMPREHENSION RIGHT HEMISPHERE LPT LESION LEFT POSTERIOR TEMPORAL LESIONS NO COMPREHENSION DEFICITS RIGHT HEMISPHERE LESIONS + COMPREHENSION DEFICITS

Typical Developmental changes in Language Processing: an ERPs study Children at 13 - and 20 -months were tested on a “known” and “unknown” word comprehension task (ERPs recorded) At 13 mo. : Brain activation patterns were bilateral and extended from frontal through posterior temporal and parietal regions. By 20 mo. : Brain activation patterns were left lateralized over traditional language areas. Neville et al. , 1991

Language Acquisition neural networks extend bilaterally from frontal to posterior areas whereas With learning and experience, Language networks become Left Lateralized and localized areas more efficient for language processing

Narrative Production in School-age Children with Early Injury By age 7, mastered basic semantic and grammatical features of language. within the normal range on all measures of lexical (age 5) and morphosyntactic development However, they used complex syntax and narrative structures less frequently than typical children, even by 12 yr subtle deficits

Summary: Language in Children with Early Brain Lesions 1. All children were delayed in some aspect of language regardless of the lesion side. 2. Opposite profile from adult lesion populations RIGHT HEMISPHERE INJURY IS ASSOCIATED WITH DEFICITS IN WORD COMPREHENSION. LEFT POSTERIOR TEMPORAL INJURY IS ASSOCIATED WITH DEFICITS IN WORD AND GRAMMATICAL PRODUCTION.

Summary: Language in Children with Early Brain Lesions 3. Subtle deficits persistent over time BY AGE 5, CHILDREN APPEAR TO “CATCHUP. ” THEY SCORE WITHIN THE NORMAL RANGE ON MEASURES OF SEMANTICS AND GRAMMATICAL MORPHOLOGY. NO SITE SPECIFIC EFFECTS OBSERVED AFTER AGE 7 (AGE 5 FOR LEXICAL DEFICITS).

Summary: Language in Children with Early Brain Lesions HOWEVER, ALTHOUGH THEY SCORE WITHIN THE NORMAL RANGE, THEY TEND TO USE LESS COMPLICATED LANGUAGE FORMS 4. BILATERALLY DISTRIBUTED LANGUAGE NETWORKS in Typical Developing Infants can in part explain the nature of recovery/development in this population

Spatial Cognitive Development in Children with Early Focal Brain Injury

SPATIAL ANALYSIS The ability to specify both the parts and the overall configuration of a visually presented pattern, and to understand how the parts are related to form a whole. Spatial analysis thus involves the ability: to segment a pattern into a set of constituent parts § to integrate those parts into a coherent whole §

Visual Pattern Processing Segmentation of the parts Front Integration of parts into a whole Back LEFT HEMISPHERE Front Back RIGHT HEMISPHERE

MEMORY REPRODUCTION: ADULT LESION PATIENTS

PATTERNS OF SPATIAL DEFICIT IN ADULTS WITH RIGHT AND LEFT POSTERIOR BRAIN INJURY Ø LEFT POSTERIOR BRAIN INJURY: Impairs ability to define and encode the parts of a spatial array. • Oversimplification of spatial patterns • Omission of pattern detail • rely on overall configural cues and ignore specific elements of spatial patterns. Ø RIGHT POSTERIOR BRAIN INJURY: Impairs ability to integrate pattern elements into a coherent whole. • Focus on the parts or elements of the pattern • Able to produce or report the parts of a form but fail to attend to the overall configuration.

FUNCTIONAL MAGNETIC RESONANCE IMAGING (FMRI) OF TYPICAL ADULTS

Part-Whole Stimulus S S S S SS S S S Two tasks: 1. Attend to the WHOLE. 2. Attend to the PARTS.

Adult Brain Activation on the Part-Whole Processing Task Attend to the Whole: Right > Left RIGHT LEFT Attend to the Part: Left > Right Back Front

VISUOSPATIAL PROCESSING IN CHILDREN WITH EARLY BRAIN INJURY

MODEL HIERARCHICAL FORMS FOR THE MEMORY REPRODUCTION TASK

Examples from 5 -year-olds (5 yrs, 4 mo) (5 yrs, 7 mo) (5 yrs, 8 mo) Longitudinal examples from normal controls MODEL (6 yrs, 10 mo) (6 yrs, 3 mo) (6 yrs, 5 mo) MODEL (7 yrs, 10 mo) (9 yrs, 3 mo)

3 Children with LEFT Hemisphere Stroke: LOCAL Processing Deficit Model (5 yr, 1 mo) (6 yr, 0 mo) 3 Children with RIGHT Hemisphere Stroke: GLOBAL Processing Deficit Model (6 yr, 2 mo) (6 yr, 3 mo) (6 yr, 11 mo)

REPRODUCTION ACCURACY (5 -7 year olds and 9 -12 year olds) Control group performs equally well on global and local RH – deficit global; LH – deficit local

HOUSE DRAWINGS OF TYPICALLY DEVELOPING 3. 5 - TO 5 -YEAR OLDS

HOUSE DRAWING OF CHILDREN WITH RIGHT OR LEFT FOCAL BRAIN INJURY 4 Children with LH Lesion: LOCAL Processing Deficit 4 Children with RH Lesion: GLOBAL Processing Deficit

LEFT hemisphere brain injury RIGHT hemisphere brain injury

Attend to the Whole: Right > Left RIGHT LEFT Attend to the Part: Left > Right

SPATIAL ANALYSIS IN CHILDREN WITH EARLY FOCAL BRAIN INJURY 1. DEFICITS ARE MILDER THAN THOSE OBSERVED AMONG ADULTS WITH COMPARABLE INJURY. 2. THE PATTERNS OF DEFICIT ASSOCIATED WITH LEFT OR RIGHT POSTERIOR INJURY ARE SIMILAR IN ADULTS AND CHILDREN.

SPATIAL ANALYSIS IN CHILDREN WITH EARLY FOCAL BRAIN INJURY 3. DEFICITS ARE PERSISTENT BUT MILD AND OFTEN NOT EVIDENT ON THE SAME MEASURES OVER TIME. DEFICITS ARE MOST EVIDENT ON TASKS THAT ARE CHALLENGING FOR NORMALLY DEVELOPING PEERS. FOR MOST TASK, CHILDREN EVENTUALLY ACHIEVE CEILING LEVELS OF PERFORMANCE - AT LEAST FOR MEASURES OF PRODUCT. 4. SOME EVIDENCE FOR DEVELOPMENT OF COMPENSATORY STRATEGIES. NEW TECHNIQUES FOR ASKING QUESTIONS ABOUT PATTERNS OF NEURAL ORGANIZATION: FUNCTIONAL IMAGING.

Conclusions Ø Brain development is a dynamic, adaptive process. Ø The capacity for brain adaptation is evident from the earliest point in development. Ø Studies of children with focal brain injury illustrate the plasticity of the developing brain, that is the ability to organize differently, to adapt. Ø But these same studies also point to limits on plasticity.

… Question?

Nature v Nurture NATURE § Most of the information necessary to build a human brain is latent within the genes. § Development consists of a process of a maturationally –defined unfolding or triggering of the information contained within the genes. § Deviation from that essential plan is an anomaly requiring exceptional developmental mechanisms.

. . . Nature vs. Nurture NURTURE § Most of the information that shapes the human mind comes from the structure of the external world. § Some experiences are common experience while others are unique to the individual. § Development is a process of progressive differentiation of functionally equipotential cortical tissue.

An Alternative View § BOTH Nature and Nurture matter. § Neither is a sufficient account of the development of brain-behavior relations. § They influence one another -- i. e. they INTERACT.

An example of Nature X Nurture Interaction Activity Dependent Competition and Cell Death Intrinsic cue Nerve Growth Factor (NGF) Extrinsic cue Sensory stimulation (i. e. , Neuronal Activity ) Cells compete for NGF, the ones that activate first and most for make connections and get NGF, the others die.