Visuomotor adaptation to a small mirror reversal perturbation


Previous research has shown that implicit processes underlie reach adaptation to a visuomotor distortion that results in a consistent change in movement direction (e.g., cursor feedback is rotated 10° clockwise to hand motion, regardless of which target is displayed). The current research looked to determine if implicit processes play a role in visuomotor adaptation in response to a mirror reversal distortion, where visual feedback of hand motion is reversed across the y-axis and hence changes in movement direction are required for different targets. Participants reached towards a left and right target positioned 5° to the left and right of body midline with (i) aligned cursor feedback and (ii) mirror reversed cursor feedback, such that reaching to the left target caused the visual cursor to shift 5° to the right of the midline, and reaching to the right target caused the cursor to shift 5° to the left of the midline, creating a 10° mirror reversal. Following both aligned and mirror reversed trials, participants reached without a cursor to assess implicit adaptation. Angular errors at peak velocity early in the mirror reversed trials showed evidence of adaptation, such that reaches were adjusted to aim towards the right side of the midline when reaching to the left target and vice versa when reaching to the right target. These errors continued in the no cursor trials, providing evidence of implicit adaptation. Thus, our results indicate a role for implicit processes in visuomotor adaptation to a small mirror reversal.