Dynamic Coordination of Body Parts During Prism Adaptation

1 Department of Anatomy and Neurobiology and 2 Department of Neurology and Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri, 63110; and 3 Division of Biology, California Institute of Technology, Pasadena, California 91125 Martin, Tod A., Scott A. Norris, Bradley E. Greger, and W. Thomas Thach. Dynamic Coordination of Body Parts During Prism Adaptation. J. Neurophysiol. 88: 1685-1694, 2002. We studied coordination across body parts in throwing during adaptation to prisms. Human subjects threw balls at a target before, during, and after wearing laterally shifting prism eyeglasses. Positions of head, shoulders, arm, and ball were video-recorded continuously. We computed body angles of eyes-in-head, head-on-trunk, trunk-on-arm, and arm-on-ball. In each subject, the gaze-throw adjustment during adaptation was distributed across all sets of coupled body parts. The distribution of coupling changed unpredictably from throw to throw within a single session. The angular variation among coupled body parts was typically significantly larger than angular variation of on-target hits. Thus coupled body parts changed interdependently to account for the high accuracy of ball-on-target. Principal components and Monte Carlo analyses showed variability in body angles across throws with a wide range of variability/stereotypy across subjects. The data support a model of a dynamic and generalized solution as evidenced by the distribution of the gaze-throw adjustment across body parts.