Effect of practice on the control of reach extent

The control of reaches to targets that vary in distance involves a combination of anticipatory planning and feedback-based adjustments. However, it is not known if their contributions to the control of reach extent change with repetitive practice. This study investigated the effect of three days of practice on the control of reach extent. Right-hand dominant participants reached with either the non-dominant left arm or dominant right arm to six targets presented in two directions and three distances in a virtual environment. The effect of practice on planning and feedback-based adjustments to control reach extent was examined by determining how well peak acceleration and time to peak velocity predicted the eventual distance moved, respectively. Both arm groups demonstrated improvements in reach performance (decreased endpoint error and movement time). The Left Arm group demonstrated an increased use of anticipatory planning and feedback-based adjustments to control reach extent with practice while the Right Arm group did not show a change. Changes in the control of reach extent seen in the Left Arm group may reflect experience-dependent creation of a more robust internal model of the arm and/or increased weighting of control mechanisms from the dominant left-brain hemisphere. The potential to modify the use of anticipatory planning and feedback-based adjustments to control reach movements may be relevant for rehabilitation approaches in clinical populations such as stroke who have altered control of reach extent.