Comparison of reward modulation in the frontal eye field and caudate of the macaque

The frontal eye field (FEF) influences saccade generation via direct projections to the superior colliculus and an indirect pathway through the basal ganglia. To test whether different reward information is represented in the FEF and the basal ganglia, we recorded from the FEF and the caudate nucleus in monkeys performing an asymmetrically rewarded memory-guided saccade task. Aperipheral cue at one of two opposing positions was flashed briefly to indicate the saccade target. In a given block, one position was associated with big reward and the other with small reward. Big-reward position was alternated between blocks. In this task, the FEF and caudate displayed similar prevalence of neuronal activity before cue onset that was larger in blocks with specific big reward-cue position associations. They also exhibit comparable reward modulation of visual responses that were spatially selective. In contrast, visual responses that were specific to expected reward size, instead of spatial locations, were commonly observed in caudate but rarely seen in the FEF. Thus, both the FEF and basal ganglia may contribute to reward bias in saccade generation, with the FEF providing spatially relevant reward information and the basal ganglia providing additional reward-specific information.