Download Brain Development

Brain Development
• Neurogenesis: Proliferation of neurons
through cell division
• Neurons migrate to final destination in the
nervous system
• Once in place, neurons first grow an axon and
then dendrites
• Axons elongate as they grow toward specific
targets
– Myelination begins prenatally and continues at least
into adolescence
• Dendrites undergo “arborization”
– Increase in size and complexity of the dendritic “tree”,
including growth of spines on the branches
• Increases capacity of dendrites to form connections with
other neurons
• Synaptogenesis begins prenatally but
mainly occurs postnatally
– General pattern involves overproduction of
synapses followed by synaptic “pruning”
(elimination)
– This general pattern occurs at different times
in different areas of the brain
• In general, more frequently activated
synapses are more likely to be maintained
(“use it or lose it”)
• Environmental experiences play a role in
maintenance and pruning of synapses
Experiential Mechanisms in Brain Development
• Experience-expectant synaptogenesis
– Occurs as a result of species-typical experiences
• Ex: Visual cortex “expects” exposure to light and
patterned visual information—needs these sensory
inputs to develop normally
• Experience-dependent synaptogenesis
– Occurs as a result of idiosyncratic individual
experiences across the lifespan
• Ex: String musicians have more connections in
the area of the cortex representing the fingers of
the left hand