Saccadic output is influenced by limb kinetics during eye-hand coordination.

In several recent studies, saccadic eye movements were found to be influenced by concurrent reaching movements. The authors investigated whether that influence originates in limb kinematic or kinetic signals. To dissociate those 2 possibilities, the authors required participants (N = 6) to generate pointing movements with a mass that either resisted or assisted limb motion. With practice, participants were able to generate pointing responses with very similar kinematics but whose kinetics varied in a systematic manner. The results showed that saccadic output was altered by the amount of force required to move the arm, consistent with an influence from limb kinetic signals. Because the interaction occurred before the pointing response began, the authors conclude that a predictive signal related to limb kinetics modulates saccadic output during tasks requiring eye-hand coordination.