LEARNING OF SCALING FACTORS AND REFERENCE AXES FOR REACHING MOVEMENTS

To further understand visuomotor transformations in reaching, we compa red adaptation to display rotation and altered gain in planar movement s. Healthy subjects moved a cursor on a screen by moving an indicator on a horizontal digitizing tablet with their unseen hand. Adaptation t o rotation was less complete and was accompanied by markedly increased directional variability. Adaptation training on a single target gener alized broadly for gain change, but poorly for rotation. We propose th at the difficulty in adapting to rotation arises from the substantial demands on short-term working memory imposed by the need to determine the new reference direction. Adaptation to gain change makes more mode st demands on short-term memory to recalibrate the visuomotor scaling factor.