Updating working memory for words: A PET activation study

A PET study of 10 normal individuals was carried out to investigate the cer ebral regions involved in the controlled updating of verbal working memory Subjects viewed single concrete words on a computer monitor and detected oc casional target words in an attended color. In the activating condition, a target was defined as a word that was identical to the previous word presen t-ed in the attended color. In the control condition, the target was a pred esignated word. The same word lists, target probabilities, and target respo nse demands were used for both conditions, with interword intervals constra ined to ensure equivalence in the demand for target rehearsal. A comparison of the conditions found bilateral activation of dorsolateral prefrontal (m iddle frontal gyrus; MFG) and inferior parietal (supramarginal gyrus; SMG) cortical regions. Activation of the MFG is taken to reflect executive contr ol by prefrontal regions over the working memory updating process linking p osterior representations of the anticipated target stimulus to anterior rep resentations of the planned response. It is proposed that the updating of t he stimulus link is mediated via connections between the MFG and SMG. The r ole of the SMG as an amodal region binding the various modal representation s in posterior association cortex of the word being retained in working mem ory is considered and reviewed. It is suggested that the combined activatio n of these regions is related to the executive control of goal-setting in p lanned behavior. (C) 2000 Wiley-Liss, Inc.