Trained movement direction influences reach adaptation independent of proprioceptive recalibration


Reaching with rotated visual feedback of the hand leads to reach adaptation and shifts in felt hand position (i.e. proprioceptive recalibration). We have previously shown that proprioceptive recalibration generalizes across a greater area of the workspace than reach adaptation (Lombardo et al. 2014). In the current study we looked to determine if these different generalization patterns are dependent on the movement direction (i.e. vector) experienced during reach training. Subjects trained to reach to a single target with distorted hand-cursor feedback from one of two start positions (S1 = aligned with body midline and S2 = 21 cm to the right of S1). Cursor feedback was rotated 30° clockwise relative to subjects' actual hand position. Subsequently, subjects reached without visual feedback to (1) the same target; (2) the same target from the other start position; and (3) a novel target. Subjects also estimated their felt hand position after moving out from both start positions in order to determine the position at which they perceived their hand was aligned with the reach targets. Results indicated that proprioceptive recalibration generalized to a greater extent than reach adaptation regardless of the movement vector experienced during reach training trials. Interestingly, generalization patterns of reach adaptation differed depending on the trained start position such that subjects tended to move to similar goal locations experienced during training from S1 but not from S2. Together, these findings suggest that the movement vector experienced during training does not influence proprioceptive recalibration but changes the processes involved in reach adaptation.

Acknowledgments: This study was supported by NSERC.