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Abstract:
Using functional magnetic resonance imaging, we investigated
whether specific brain regions mediate cognitive processes needed
for predicting task order or timing during task switching. Two
discrimination tasks were used: vowel/consonant and case
discrimination. The results show that task switching, when compared
to baseline, activated a bilateral prefronto-parietal cortical
network. This network was not selective for task switching because
it was also activated when maintaining two task-sets without
switching between them. However, subjects with greater activation
in the left dorsolateral prefrontal cortex showed a reduction of
the response times alternation cost (responses times difference
between mixed and pure block of trials), suggesting that this brain
region was mediating a type of control mechanism. Anticipating task
order activated the anterior medial prefrontal cortex and the right
hippocampus, while anticipating task timing activated the left
fronto-polar cortex. In contrast, when task order could not be
predicted, the dorsolateral prefrontal cortex was activated
bilaterally. These results indicate that when a subject is required
to switch between tasks, distinct brain regions are responsible for
the processing of specific aspects of the switching routine.
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