2/12/15 – Lecture 9 – Neural Development Pt 2: Effects of Postnatal Maturation and the Environment on Neural Development- Goal: to explain how postnatal maturation and experiences are associated with changes in neural structure and function- Brain Developmento Grasping Motor Behaviors: ~2 months – hands orients toward object and gropes to hold ~4 months – grasps with entire hand “palmer grasp” ~6-8 months – “mature” grasp using fingers individually ~10 months – fine “pincer” grasp for holding small objects - Neural Changes and Grasping Motor Behaviorso Increased dendritic maturation in motor cortex neuronso Increased myelination of motor cortex neurons at both later stages of grasp developmento Decreases in cortical thickness in the hand region of the motor cortex, may reflect pruning of less effective motor neurons and synapses and selection of the strongest connectionso Language Development: environment affects language acquisition  12 months – vocabulary starts to form (5-10 words) 24 months – 200-300 words 36 months – 500-1000 words and ability to form sentences starts 72 months – 2500 words- Major Neural Changes and Language Developmento 1) increased cortical thickness in speech areas of cortex for the language the child is hearing and speaking Increase in glial cells Increased dendritic branching and synaptogenesis Myelinationo 2) pruning of neurons and synapses in speech sound areas of other languages not being heard or spoken Children raised in bilingual homes will keep more speech sound synapses Loss of speech sound synapses during development makes it harder to learn new languages in adulthood- It requires the formation of new synapses whichis more difficult that keeping or strengthening existing oneso Problem Solving: Piagetian Stages of Development Sensorimotor Stage: birth-2 years old … object permanence, cause and effect Preoperational Stage: 2-6 years old … form mental, word, imagination/ creativity,drawing representations of things, ego-centrism, and the attribution of human intentions and reasoning to inanimate objects Concrete Operations: 7-11 years old … mentally manipulate dimensions, mathematics, conservations of mass- Inductive reasoning: I know internally it will occur (build on what you know)- Deductive reasoning: someone else describes something and you can accept that it will happen (build on new information) Formal Operations: 11 years and forward … abstract reasoning, strategy- Neural Changes and Piagetian Stageso Spurts of brain growth accompany or precede the changes in Piagetian developmento Neuronal number doesn’t change but glial cells and synaptic density probably increase- Brain Development and the Environmento Enriched Environments and Neural Development in Animals (rats) Rats raised in an enriched environment preform better on cognitive tasks like solving mazes than rats raised in standard cages- Neural Changes to enriched Environments and Neural Complexity in Animalso Cortical and hippocampal neurons from rats raised in enriched environments are larger, have more complex dendritic branchingand more synaptic connections than the control ratso Adult Neurogenesis: new neurons formed in the hippocampus, area size increased when raised in a rich environment- Exercise also increases postnatal hippocampal neurogenesiso Rats given a cage wheel to run on had equal or greater neuronalproliferation as rats raised in an enriched environment Could explain some of the well-established cognitive benefits of regular exerciseo Enriched Environments and Neural Development in Humans Environmental enrichment may reflect the influence of our experiences on the pruning of synapses- Children in poor environments show severe cognitive, language, social, and motor defects- Conversely, children who are bilingual often have greater cortical activation than children who speak one language, which probably reflects that maintenance of synapses and neurons from two different language sound areas of the cortexo Children exposed to music early in life are more likely to developmusical abilities later in lifeo What can influence postnatal hippocampal neurogenesis Diet – omega 3 oils/ good diets support and promote growth, fat and sugars/ bad diets suppress growth Alcohol, Drugs – can extremely suppress and kill hippocampal neurons Stress and lack of sleep Aging – part of why it’s harder to learn things as you age- Developmental Disorders: Autism Spectrum Disorder and Mental Retardationo Autism Spectrum Disorder: family of disorders characterized by social deficits, communicational difficulties, stereotyped or repetitive behaviors and interests, and in some cases, cognitive delays Symptoms: now affects >1 in 68 male live births in the US- Reduced ability to interpret the emotions and intentions of others- Reduced capacity for social interaction and communication- Preoccupation with a single object or activity – spinning or flapping- About 75% suffer from mental retardation and 35% suffer from epilepsy- Some have (<10%) cognitive abilities that are superior – savantso However, autism is a very heterogeneous disorder and patients typically don’t display the same pattern of deficits (no one will have the exact same expressions of the disorder) Key Neural Changes in Autism- Under-Connectivity Hypothesis: some brain regions are smaller or less well connected in autistic brainso 1) hippocampus and amygdala – emotion processingo 2) insular cortex – social processingo 3) brainstem nuclei – hearing and recognizing facial expressions Could reflect defective proliferation of neurons, defects in dendritic branching and synapse formation, or excessive pruning- Over-Connectivity Hypothesis: some brain regions are larger or overly connected in autistic brainso 1) basal ganglia and motor cortex - repetitive movementso 2) sensory cortex – fixation with certain sensory stimulio 3) frontal cortex – immersion in own thoughts Overgrowth may reflect excessive neuron or synapse formation and/or defective pruning of cells or synapseso Mental Retardation: a generalized disorder characterized by significantly impaired cognitive functioning and deficits in adaptive behavior Causes: 1 in 30-50 live births in the US- Genetics - trisomy 21 and other inherited genetic disorders- Malnutrition or iodine deficiency – in the 3rd world mainly- Birth