Evolutionary perspectives on language and brain plasticity

Our understanding of speech and language disorders may be aided by informat ion about the constraints and predispositions contributed by neural develop mental processes. As soon as we begin to look at human neuroanatomy and dev elopment from a comparative perspective, it is possible to recognize a numb er of ways that human brains diverge from the general pattern of other ape and monkey brains. These divergences may offer dues to language evolution. Large-scale quantitative changes in the relative proportions of brain regio ns (as opposed to just overall expansion) offer some of the most obvious cl ues. Additional information about how axons are guided in their extensions to distant developmental targets and how competitive trophic processes scul pt these connections also provides a way to understand how gross quantitati ve changes in cell numbers could affect circuit organization and ultimately behavior. (C) 2000 by Elsevier Science Inc.