SEMANTIC NETWORKS IN THE DIVIDED CEREBRAL HEMISPHERES

Abstract— Hemispheric differences in the recognition and manipulation of meaning may be based on distinctions in size, composition, or organization of the right and left semantic networks. The present study describes these features of pictorially based semantic networks in 3 subjects with complete forebrain commissurotomy. Stimuli were presented for prolonged viewing to the left and right visual hemifields. For each trial, the subjects chose from a 20-choice array all pictures that were associated with a target, then indicated the member of each pair of chosen associates that was more closely related to the target. The hemispheres' networks were found to be of similar size and composition, but were organized differently. The right hemisphere more often produced linear rankings of semantic associates to a target than did the left, and rankings by the two hemispheres were not strongly correlated. Hemispheric differences in semantic organization mirror differences in perceptual organization, with the right hemisphere specialized for conventional meaning and the left hemisphere specialized for detecting and processing deviations from standard meaning.