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Abstract:
Although central to many theories of cognitive function and
dysfunction, the concept of a central executive (CE) that
coordinates cognitive processes is poorly understood. Using fMRI,
we attempted to identify the neuroanatomical bases of the CE with
tasks designed to engage specific executive functions. We propose
that a CE taxonomy can be informed by an understanding of the
similarities and differences in the neuroanatomical underpinnings
of putatively distinct executive functions. Two CE functions have
been studied: inhibitory control and the allocation of attentional
resources within working memory. The first task, employing an
event-related fMRI design, required occasional response inhibition
to lures as subjects made frequent responses to visual targets. The
second task manipulated the frequency of attention switches between
two running counts in working memory. The temporal specificity of
the first task and parametric manipulation of the second allow
better isolation of the activation specific to the CE. Both tasks
revealed frontal, parietal and cerebellar activations, indicating a
distributed neuroanatomical basis for the CE. Both tasks activated
overlapping regions of the right middle frontal gyrus. However,
whereas the inhibitory task predominantly activated the right
hemisphere (dorsolateral and inferior frontal regions) and
cingulate, the attention switching task activated more posterior
regions of the left inferior frontal gyrus. These different
activation patterns suggest a separate neuroanatomical substrate
for each CE function thereby attesting to their distinctiveness.
Supported by grant DA09465.
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