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Encyclopedia of Psychology Alan E. Kazdin, PhD, Editor-in-Chief

BRAIN DEVELOPMENT

Although many aspects of neural tube formation are controlled by gene activity of cells in the plate itself, some of the patterning arises from gene activity in the tissue just below it (mesoderm)

Much of early brain development is tightly regulated by genetic constraints and is relatively insensitive to the environment. Clearly, it is advantageous for early brain development not to be very sensitive to changes in chemical concentrations, body temperature, or nutrition.

It is somewhat surprising, but normal, for the brain to produce an overabundance of primitive cells and then have them die in a programmed, genetically controlled fashion (apoptosis). This species-specific program of cell death presumably reflects the evolutionary modification of preexisting programs, changing the developmental path toward a species-specific brain.

In the development of cerebral cortex, for example, the neuroblasts are formed on the inner surface of the neural tube and must travel a substantial distance, a process that continues for months after birth in humans. Just as neurogenesis is often precisely timed, neuron migration often proceeds in tightly coordinated “waves” of movement, sometimes with neurons having similar birth dates all arriving in a similar location.

For example, radial glial cells form a stringlike shape spanning the cerebellar cortex that neuroblasts use as a guide to “climb” down from their birth place to their ultimate destination in the granule cell layer. In addition to physical constraints on migration, nearby cells are covered with molecular markers that signal some neurons to stop and others to pass by, and soluble factors are also released that mark target locations

Tags: encyclopedia of psychology
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