AUDITORY AND VISUAL WORD-PROCESSING STUDIED WITH FMRI

Brain activations associated with semantic processing of visual and au ditory words were investigated using functional magnetic resonance ima ging (fMRI). For each form of word presentation, subjects performed tw o tasks: one semantic, and one nonsemantic. The semantic task was iden tical for both auditory and visual presentation: single words were pre sented and subjects determined whether the word was concrete or abstra ct. In the nonsemantic task for auditory words, subjects determined wh ether the word had one syllable or multiple syllables. In the nonseman tic task for visual words, subjects determined whether the word was pr esented in lower case or upper case. There was considerable overlap in where auditory and visual word semantic processing occurred. Visual a nd auditory semantic tasks both activated the left inferior frontal (B A 45), bilateral anterior prefrontal (BA 10, 46), and left premotor re gions (BA 6) and anterior SMA (BA 6, 8). Left posterior temporal (midd le temporal and fusiform gyrus) and predominantly right-sided cerebell ar activations were observed during the auditory semantic task but wer e not above threshold during visual word presentation. The data, when averaged across subjects, did not show obligatory activation of left i nferior frontal and temporal language areas during nonsemantic word ta sks. Individual subjects showed differences in the activation of the i nferior frontal region while performing the same task, even though the y showed similar response latency and accuracy. (C) 1999 Wiley-Liss, I nc.