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Abstract:
A set of neural structures, including anterior parietal,
lateral prefrontal, and anterior cingulate cortices, has been shown
to become more active when unwanted stimulus information is
presented during the performance of choice reaction time tasks. The
present study examined which of these regions are specifically
related to the resolution of interference between conflicting
response codes. Whole-brain fMRI data were acquired for 10 healthy
adults (5 M, 5 F; mean age = 27) as they performed a flanker task.
On each trial, subjects pressed one of two buttons in response to a
centrally presented letter (the target), while ignoring two
flanking stimuli (flankers), which differed from the target. The
flankers were associated with the same response as the target on
Congruent trials, the opposite response on Incongruent trials, and
no response on Neutral trials. Regions that were more active for
Incongruent than Congruent trials were presumed to be involved in
resolving competition between opposing response associations.
Regions that were more active for Congruent than Neutral trials
were presumed to be involved in retrieving stimulus-response
associations from long-term memory. We observed a partial
dissociation whereby most lateral prefrontal regions and the
anterior cingulate gyrus were associated with response competition,
whereas most non-prefrontal regions, including left parietal
cortex, were associated with response code activation.
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