Transfer of saccadic adaptation to the manual motor system

When a saccade target is shortened in amplitude during the eye movement towards it, subjects will initially overshoot the displaced target and make secondary movements to fixate it. Nevertheless, after a few trials the eye adapts and goes directly to the final displaced target position. The aim of the present study was to examine whether hand pointing will be influenced by saccadic adaptation. We found that pointing movements of an unseen hand were shorter when the eye was adapted compared to when the eye was unadapted, thus demonstrating a transfer of the modification of the oculomotor system to the manual motor system. These results have important implications for the mechanisms that underlie goal-directed eye and hand movements. In particular, it seems that the two systems may use a common signal to specify eye and arm localization.