Selective use of perceptual recalibration versus visuomotor skill acquisition

Exposure to laterally displacing prisms is characterized by systematic misr eaching in the opposite direction after prisms are removed. Other learning tasks involving altered visuomotor mappings can often be mastered by the su bject with minimal resulting aftereffects. One variable that may account fo r this difference is the nature of the feedback provided to the subject: du ring studies of prism exposure, subjects usually view the hand itself, wher eas in many studies of visuomotor learning, subjects view a computer-genera ted representation of the hand position or movement. We compared the use of actual feedback of the hand with computer-generated representational feedb ack of its position during exposure to laterally displacing prisms. In the actual feedback condition (ACT), a light on the fingertip was illuminated i mmediately at the end of each reach. In the representational feedback condi tion (REP), a computer-generated spot of light was displayed to indicate th e exact position of the fingertip at the end of each reach. Whereas the rat e and magnitude of error correction were the same in both conditions, only the ACT condition produced the large adaptive aftereffect typically observe d after prism exposure. These results suggest that the perception of a phys ical coincidence between the feedback source and the hand may be a key fact or in determining whether adaptation is accomplished through perceptual rec alibration or visuomotor skill acquisition.