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Abstract:
Neuroimaging studies of working memory (WM) that have shown
activation in anterior prefrontal cortex (PFC; e.g., BA 10) have
typically involved the monitoring and management of subgoals during
task performance. We tested this hypothesis directly in a fMRI
study by assessing the effect of adding a subgoal processing
component during a simple WM task. Subjects were scanned while
performing two variants of the AX-CPT delayed response WM task. In
the baseline condition, subjects monitored for the presence of a
specific concrete probe word (LIME) immediately following a
specific abstract cue word (FATE). In the semantic AX-CPT
condition, subjects monitored for the presence of any concrete
probe word immediately following any abstract cue word. Thus, in
the semantic AX-CPT, subjects must semantically classify the probe
word (the subgoal task) while simultaneously maintaining the
semantic classification of the cue (WM), so that these two pieces
of information can be integrated into a target determination. A
third control condition was also performed in which subjects
performed abstract/concrete semantic classification by itself. A
right anterior PFC region was observed which showed significant
activation during the semantic AX-CPT condition, but no activity in
either the word AX-CPT or semantic classification conditions. These
results suggest that anterior PFC is selectively engaged by the
requirement to monitor and integrate subgoals during WM
tasks.
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