Mapping of semantic, phonological, and orthographic verbal working memory in normal adults with functional magnetic resonance imaging

Twelve neurologically normal participants (4 men and 8 women) performed sem antic, phonological, and orthographic working memory tasks and a control ta sk during functional magnetic resonance imaging. Divergent regions of the p osterior left hemisphere used for decoding and storage of information emerg ed in each working memory versus control task comparison. These regions wer e consistent with previous literature on processing mechanisms for semantic , phonological, and orthographic information. Further, working memory Versu s control task differences extended into the left frontal lobe, including p remotor cortex, and even into subcortical structures. Findings were consist ent with R. C. Martin and C. Romani's (1994) contention that different form s of verbal working memory exist and further suggest that a reconceptualiza tion of premotor cortex functions is needed.