Recoding, storage, rehearsal and grouping in verbal short-term memory: an fMRI study

Functional magnetic resonance imaging (fMRI) of healthy volunteers is used to localise the processes involved in verbal shortterm memory (VSTM) for se quences of visual stimuli. Specifically; the brain areas underlying (i) rec oding, (ii) storage, (iii) rehearsal and (iv) temporal grouping are investi gated. Successive subtraction of images obtained from five tasks revealed a network of left-lateralised areas, including posterior temporal regions, s upramarginal gyri, Broca's area and dorsolateral premotor cortex. The resul ts are discussed in relation to neuropsychological distinctions between rec oding and rehearsal, previous neuroimaging studies of storage and rehearsal ; and, in particular, a recent connectionist model of VSTM that makes expli cit assumptions about the temporal organisation of rehearsal. The functiona l modules of this model are tentatively mapped onto the brain in light of t he imaging results. Our findings are consistent with the representation of verbal item information in left posterior temporal areas and short-term sto rage of phonological information in left supramarginal gyrus. They also sug gest that left dorsolateral premotor cortex is involved in the maintenance of temporal order, possibly as the location of a timing signal used ill the rhythmic organisation of rehearsal, whereas Broca's area supports the arti culatory processes required for phonological recoding of Visual stimuli. (C ) 2000 Elsevier Science Ltd. All rights reserved.