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