Effects of differential experience on the brain and behavior.

This review of plasticity of brain and behavior ranges from examples of plasticity restricted to an early critical period to other examples that show lifelong plasticity, but these two polar opposites are far from covering the field. Rather, it appears that there are a number of patterns by which different measures of plasticity vary as a function of age. Even in cases that indicate the existence of a critical period for development of neural circuits and of behavior, it is not yet possible to define the period exactly, because different methods yield different results, and much parametric work remains to be done. Nevertheless, the variety of findings of plasticity are encouraging for education and for recovery of function.