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Neural Plasticity

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Title: Neural Plasticity


1
Neural Plasticity
  • Cell death is a major mechanism of development
  • Maturation of appropriate cells and connections
    is linked to the simultaneous loss of less
    successful ones

2
Neural Plasticity
  • Roger Sperry (1913 - ) (Nobel 1981)
  • Is cell growth guided by physiology or function?

3
Neural Plasticity
  • Cells growth is guided by cell-surface molecules
  • Attraction and repulsion
  • As cells grow, their selectivity changes
  • Example
  • TOPDV
  • 30 times more concentrated in axons of dorsal
    retina than in axons in ventral retina
  • Neural Darwinism-- Competition Among Axons
  • a. far more neurons are produced than will
    survive
  • b. random reshuffling
  • during reproduction, gene mutations and gene
    re-assortment produce individuals with variations
    in structure and function
  • natural selection favors some and weeds out the
    rest
  • c. mutations in genes are random events, but
    trophic factors steer new axonal branches and
    synapses in the right direction
  • d. still the axon that forms the successful
    synapse survives

4
Neural Plasticity
  • rats--enriched vs impoverished environments
  • Running wheel
  • More neurotrophins
  • thicker cortex
  • more dendritic branching
  • improved performance on many tests of learning
  • an enriched environment enhances sprouting of
    axons and dendrites
  • Humans with extensive education tend to have
    longer and more widely branched dendrites
  • does learning promote dendritic branching or do
    people with wide dendritic branching succeed in
    school and therefore stay longer?
  • Environment enrichment can occur at any time,
    some experiences produce bigger effects if they
    occur early

5
Neurogenesis
  • Since Cajal, believed that all neurons are
    present by age 1, no new ones grow
  • But, we now know that not to be true
  • Olfactory receptors
  • On location, immature division
  • Stem cells from brain
  • Songbirds, singing area
  • Black-capped chickadee, hides seeds, grows new
    hippocampal cells
  • New cells in human adults brains?
  • Musicians temporal cortex, postcentral gyrus
  • Possibly a bad thing overlap musicians cramp,
    or focal hand dystonia
  • Could be dopaminergic action release of dopamine
    increases to expand representation of stimuli
    active at the time
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