A reinterpretation of hemispherectomy data without functional plasticity of the brain: I. Intellectual function

Abstract

A comprehensive reanalysis of post-hemispherectomy IQ, language, and other intellectual findings in patients whose brain damage occurred in infancy, childhood, or adulthood reveals no recovery advantages attributable to superior interhemispheric transfer of properties in the immature brain. Instead, recovery heterogeneity in each age group is considerable, while both individual differences within the groups and minor intergroup differences are parsimoniously explained by etiological, recovery-period, and experiential variables. The findings fail to support the presuppositions of the plasticity model: that the immature brain lacks functional asymmetry, that language acquisition must occur early in life, and that recovery from brain damage is facilitated by the brain's functional equivocality during an early, critical period.