Abstract
Previous work by ourselves and others has shown that neurons in the prefrontal cortex (PFC), the frontal eye fields (FEF) and the caudate nucleus (Cd) carry task relevant information during conditional visuomotor learning in primates. Specifically, cells in all three areas show selectivity for the impending saccade direction during cue presentation and around the time of saccadic response. To delineate the specific roles of the Cd, PFC and FEF in the choice and execution of saccades, we compared the timecourse of direction selective activity in these areas as animals performed a conditional visuomotor learning task.
Monkeys learned associations between two novel visual cues and two saccades (right or left). A delay intersposed between the cue and saccade. Once the associations were learned, they were reversed and the monkeys then relearned the opposite contingencies. As reported previously, cells in the PFC, FEF and Cd carried information about object identity, saccade direction and their association during all trial epochs. During the cue and saccade epochs, population direction selectivity appeared earliest in Cd and peaked at the time of saccade. Selectivity appeared next in the FEF and last in the PFC. Half-maximum selectivity was aligned on saccade onset in the FEF and after saccade onset in the PFC. These findings suggest that the FEF is more closely associated with the motor control of saccades while Cd activity influences the choice of saccade direction. The pattern of PFC results fit well with its proposed role in executive control.
Funded by the NINDS, NIMH, RIKEN-MIT Neurosci. Res. Cntr. and Tourette's Syndrome Association
Mark Histed and Michelle Machon helped with FEF data collection