HUMAN BRAIN LANGUAGE AREAS IDENTIFIED BY FUNCTIONAL MAGNETIC-RESONANCE-IMAGING

Functional magnetic resonance imaging (FMRI) was used to identify cand idate language processing areas in the intact human brain. Language wa s defined broadly to include both phonological and lexical-semantic fu nctions and to exclude sensory, motor, and general executive functions . The language activation task required phonetic and semantic analysis of aurally presented words and was compared with a control task invol ving perceptual analysis of nonlinguistic sounds. Functional maps of t he entire brain were obtained from 30 right-handed subjects. These map s were averaged in standard stereotaxic space to produce a robust ''av erage activation map'' that proved reliable in a split-half analysis. As predicted from classical models of language organization based on l esion data, cortical activation associated with language processing wa s strongly lateralized to the left cerebral hemisphere and involved a network of regions in the frontal, temporal, and parietal robes. Less consistent with classical models were (1) the existence of left hemisp here temporoparietal language areas outside the traditional ''Wernicke area,'' namely, in the middle temporal, inferior temporal, fusiform, and angular gyri; (2) extensive left prefrontal language areas outside the classical ''Broca area''; and (3) clear participation of these le ft frontal areas in a task emphasizing ''receptive'' language function s. Although partly in conflict with the classical model of language lo calization, these findings are generally compatible with reported lesi on data and provide additional support for ongoing efforts to refine a nd extend the classical model.