In a delayed-response task, response selection marks an important transition from sensory to motor processing. Using event-related functional magnetic resonance imaging, we imaged the human brain during performance of a novel delayed-saccade task that isolated response selection from visual encoding and motor execution. The frontal eye fields (FEFs) and intraparietal sulcus (IPS) both showed robust contra-lateralized activity time-locked to response selection. Moreover, response selection affected delay-period activity differently in these regions; it persisted throughout the memory delay period following response selection in the FEF but not IPS. Our results indicate that the FEF and IPS both make important but distinct contributions to spatial working memory. The mechanism that the FEF uses to support spatial working memory is tied to the selection and prospective coding of saccade goals, whereas the role of the IPS may be more tied to retrospective coding of sensory representations.
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