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Abstract:
Neuroimaging studies show that prefrontal, premotor and
parietal cortical regions constitute a working memory network that
supports the active retention of information. We used fMRI to
examine the influence of information content and memory load on the
neuroanatomical and functional characteristics of this network.
Subjects performed a modified delayed matching-to-sample task that
allowed the examination of content-specific retention processes,
independently of perceptual and encoding processes. In Experiment
1, non-verbalizable objects and spatial locations had to be
memorized for 4 sec. In Experiment 2, human faces and butterflies
were used as stimuli during a 6 sec retention interval. All tasks
activated similar cortical regions including posterior parietal
(banks of the intraparietal sulcus), premotor and prefrontal
regions (banks of the inferior precentral and inferior frontal
sulcus). This activation pattern was left lateralized for objects
and faces and more bilateral for spatial locations. Consistent with
previous studies, these results indicate that working memory
networks show content-specific hemispheric weightings. Longer
retention times (in Experiment 2) elicited a larger proportion of
prefrontal and premotor activation, whereas the posterior parietal
activation was not affected by retention duration. These results
suggest a functional segregation of the network components with
posterior parietal areas being more involved in visuo-spatial
processes of retention and the premotor/prefrontal regions being
more concerned with mnemonic aspects (funded by the DFG).
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