Patterns of transfer of adaptation among body segments

Two experiments were conducted in order to determine the patterns of transf er of visuomotor adaptation between arm and head pointing. An altered gain of display of pointing movements was used to induce a conflict between visu al and somatosensory representations. Two subject groups participated in Ex periment wi: group 1 adapted shoulder pointing movements, and group 2 adapt ed wrist pointing movements to a 0.5 gain of display. Following the adaptat ion regimen, subjects performed a transfer test in which the shoulder group performed wrist movements and the wrist group performed shoulder movements . The results demonstrated that both groups displayed typical adaptation cu rves, initially undershooting the target followed by a return to baseline p erformance. Transfer tests revealed that both groups had high transfer of t he acquired adaptation to the other joint. Experiment 2 followed a similar design except that group 1 adapted head pointing movements and group 2 adap ted arm pointing movements. The arm adaptation had high transfer to head po inting while the head adaptation had very little transfer to arm pointing. These results imply that, while the arm segments may share a common target representation for goal-directed actions. individual but functionally depen dent target representations may exist for the control of head and arm movem ents. (C) 2001 Elsevier Science B.V. All rights reserved.