16 Early Hemisphere Specialization and Interhemisphere Plasticity: An Empirical and Theoretical Review

This chapter discusses the early hemisphere specialization and interhemisphere plasticity. It reviews the methods available for the study of hemisphere specialization in children, and indicates their associated methodological and conceptual difficulties. The chapter indicates and reconcile some of the inconsistent results of the three subsets of data relevant to left-hemisphere specialization in childhood: (1) the evidence for very early left-hemisphere specialization for language functions; (2) the data concerning the role of the right hemisphere in language functions in childhood; and (3) the evidence for early hemisphere equipotentiality for and transferability of speech and language functions. The chapter also discusses possible theoretical framework of early cerebral organization that proposes functioning and specialization of the left and right hemispheres for their respective cognitive functions at the time of birth; and that allows for such specialization to be coexistent with early participation of the right hemisphere in speech and language functions and with interhemisphere plasticity for speech and language functions, and to be subject to environmental factors and individual differences. Several new strategies and procedures to study early hemisphere specialization have been developed.