The Role of Frontoparietal Cortex across the Functional Stages of Visual Search.

Areas in frontoparietal cortex have been shown to be active in a range of cognitive tasks and have been proposed to play a key role in goal-driven activities (Dosenbach, N. U. F., Fair, D. A., Miezin, F. M., Cohen, A. L., Wenger, K. K., Dosenbach, R. A. T., et al. Distinct brain networks for adaptive and stable task control in humans. Proceedings of the National Academy of Sciences, U.S.A., 104, 11073-11078, 2007; Duncan, J. The multiple-demand (MD) system of the primate brain: Mental programs for intelligent behavior. Trends in Cognitive Sciences, 14, 172-179, 2010). Here, we examine the role this frontoparietal system plays in visual search. Visual search, like many complex tasks, consists of a sequence of operations: target selection, stimulus-response (SR) mapping, and response execution. We independently manipulated the difficulty of target selection and SR mapping in a novel visual search task that involved identical stimulus displays. Enhanced activity was observed in areas of frontal and parietal cortex during both difficult target selection and SR mapping. In addition, anterior insula and ACC showed preferential representation of SR-stage information, whereas the medial frontal gyrus, precuneus, and inferior parietal sulcus showed preferential representation of target selection-stage information. A connectivity analysis revealed dissociable neural circuits underlying visual search. We hypothesize that these circuits regulate distinct mental operations associated with the allocation of spatial attention, stimulus decisions, shifts of task set from selection to SR mapping, and SR mapping. Taken together, the results show frontoparietal involvement in all stages of visual search and a specialization with respect to cognitive operations.