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Abstract:
Abstract: Theories of cognitive control suggest two processes
are necessary for adaptive behavior: strategic processes, such as
selective attention, which provide top-down support for task
operations; and evaluative processes, such as conflict monitoring,
which provide on-line feedback about ongoing performance. Previous
studies have found DLPFC and the anterior cingulate cortex (ACC)
show increased activation with increased task demands, suggesting a
role in control processes. However, the contribution of each area
to control remains controversial. This study used event-related
fMRI and a task-switching Stroop paradigm to examine whether the
strategic/evaluative distinction could be used to dissociate DLPFC
and ACC. For each trial, subjects were instructed to either
color-name or word-read, then responded to a colored-word stimulus.
Images were acquired every 2.5" (10 images/trial, 3.75 mm3
resolution). RT data showed the expected Stroop effect. Because
color-naming requires more selective attention than word-reading,
regions associated with maintaining the attentional set should
activate following the color-naming instruction. L.DLPFC showed
this pattern, and greater activation correlated with smaller Stroop
effects (r=-.63). Because incongruent stimuli ("RED" in blue ink)
produce more conflict than congruent stimuli ("RED" in red ink),
conflict monitoring regions should activate on incongruent
color-naming trials. ACC showed this pattern, and greater
activation correlated with greater Stroop effects (r=.41). This
suggests DLPFC contributes to strategic and ACC contributes to
evaluative processes in cognitive control.
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