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Abstract:
Using fMRI we explored the neural implementation of verbal
and visuospatial working memory both during non-interfering and
interfering conditions due to articulatory and visuospatial
suppression. We observed activations related to verbal memory in
left premotor cortices including Brocas area, in the left
intraparietal sulcus and right cerebellum, and activity related to
visuospatial memory bilaterally in the posterior superior frontal
sulcus, in superior parietal regions, and in the lateral
occipitotemporal sulcus. Candidate regions for domain-specific
interference effects included the left precentral gyrus for
articulatory suppression, and almost the complete network
subserving visuospatial memory for visuospatial suppression.
Memory-related activity in these regions was significantly reduced
during suppression. Conversely, additional memory-task related
activations during interfering conditions occurred in a bilateral
network comprising the anterior intermediate and inferior frontal
sulcus and the supramarginal gyrus. These activations were specific
to the verbal domain, and this suggests that parts of the anterior
prefrontal cortex participate in phonological storage. This view is
supported by a behavioral study in which patients with
circumscribed brain lesions in the anterior prefrontal cortex
showed selective impairment of phonological storage. Together,
these findings corroborate the evolutionary-based model of human
working memory (Gruber, Neuroimage 11, S407, 2000) that
distinguishes an explicit verbal rehearsal mechanism from a
phylogenetically older mechanism which is also able to maintain
phonologically coded information.
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