The control of reaching to a target in standing involves the feed-forward programming of associated postural adjustments (a PAs) that decelerate the body and arm toward the target (Leonard et ai, 2009). However, little is known about the control of aPAs in situations where the final position of the target goal shifts after the reach movement has been initiated. We hypothesized that a predictive reprogramming of the aPA would occur prior to the adjustment of the arm movement to ensure correct execution of the reaching movement. Using a double step paradigm, we investigated the postural adjustments in standing humans exposed to unexpected changes in final target position during reaching. 10 right-handed subjects stood barefoot on 2 triaxial force plates within a light array consisting of 4 LED targets spaced at 15° intervals, oriented from their midline to their right. During unperturbed reaching (POINT), subjects were asked to reach and point to 1 of the 4 targets (45°, 60°, 75°, 90°) with their right hand upon random illumination of the target at a self-selected speed.
Available at: http://works.bepress.com/pstapley/7/