Eye-hand coordination to visual versus remembered targets

It has been suggested that the basal ganglia preferentially contribute to m ovements made to remembered targets, whereas the cerebellum preferentially contributes to movements based on visual cues. Thus, it is possible that ey e-hand coordination may differ in these two types of movement. To examine t his issue we compared the response characteristics of combined eye and hand movements made towards visual versus remembered targets. In addition, the influence of the eye movement on the hand movement was investigated by comp aring the effects of visual fixation in each task. Our results demonstrated that hand movement amplitude was greater when the hand movements were prod uced in isolation versus in combination with an eye movement. This was true regardless of whether the movement was made to a visual or a remembered ta rget. This suggests that the integration of eye position information into t he manual motor response occurs at a common neural site for both tasks. By contrast, the timing between saccade and hand onsets and offsets differed i n the two conditions. This is consistent with the idea that the timing inhe rent in eye-hand coordination is the result of separate processing within e ither the basal ganglia or cerebellar systems. Taken together, the results from this study demonstrate that certain processes underlying eye-hand coor dination during movements to visual versus remembered targets share a commo n neural substrate whereas others function independently.