How active gaze informs the hand in sequential pointing movements
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Visual information is vital for fast and accurate hand movements. It has been demonstrated that allowing free eye movements results in greater accuracy than when the eyes maintain centrally fixed. Three explanations as to why free gaze improves accuracy are: shifting gaze to a target allows visual feedback in guiding the hand to the target (feedback loop), shifting gaze generates ocular-proprioception which can be used to update a movement (feedback–feedforward), or efference copy could be used to direct hand movements (feedforward). In this experiment we used a double-step task and manipulated the utility of ocular-proprioceptive feedback from eye to head position by removing the second target during the saccade. We confirm the advantage of free gaze for sequential movements with a double-step pointing task and document eye–hand lead times of approximately 200 ms for both initial movements and secondary movements. The observation that participants move gaze well ahead of the current hand target dismisses foveal feedback as a major contribution. We argue for a feedforward model based on eye movement efference as the major factor in enabling accurate hand movements. The results with the double-step target task also suggest the need for some buffering of efference and ocular-proprioceptive signals to cope with the situation where the eye has moved to a location ahead of the current target for the hand movement. We estimate that this buffer period may range between 120 and 200 ms without significant impact on hand movement accuracy.
KeywordsEye movement Hand Human Visuo-motor control
This report was prepared with support from the Economic and Social Research Council (RES-000-22-1266).
- Elliott D, Roy EA, Goodman D, Carson RG, Chua R, Maraj BKV (1993) Asymmetries in the perception and control of manual aiming movements. Can J Exp Psychol 47(3):570–589Google Scholar
- Helson WF, Starkes JL, Elliott D, Beuekers BJ (1998) Manual asymmetries and saccade eye movements in right-handers during single and reciprocal aiming movements. Cortex 34(4):513–529Google Scholar
- Prablanc C, Eschallier JF, Komilis E, Jeannerod M (1979) Optimal response of eye and hand motor systems in pointing at a visual target. I. Spatio-temporal characteristics of eye and hand movements and their relationship when varying the amount of visual information. Biol Cybern 35:113–124PubMedCrossRefGoogle Scholar
- Woodworth RS (1899) The accuracy of voluntary movement. Psychol Rev 3:1–119Google Scholar