PET EVIDENCE FOR AN AMODAL VERBAL WORKING-MEMORY SYSTEM

Current models of verbal working memory assume that modality-specific representations are translated into phonological representations befor e entering the working memory system, We report an experiment that tes ts this assumption, Positron emission tomography measures were taken w hile subjects performed a verbal working memory task, Stimuli were pre sented either visually or aurally, and a visual or auditory search tas k, respectively, was used as a control. Results revealed an almost com plete overlap between the active memory areas regardless of input moda lity. These areas included dorsolateral frontal, Broca's area, SMA, an d premotor cortex in the left hemisphere; bilateral superior and poste rior parietal cortices and anterior cingulate; and right cerebellum. T hese results correspond well with previous research and suggest that v erbal working memory is modality independent and is mediated by a circ uit involving frontal, parietal, and cerebellar mechanisms. (C) 1996 A cademic Press, Inc.