Visuomotor adaptation to constant and varying delays in a target acquisition task.

In visually guided movement tasks, visual feedback delays disrupt visuomotor control and impair performance. Adaptation then occurs as compensatory visuomotor updates are generated to accommodate the delay and recover control. Following the removal of the delay, an after-effect is observed, where the retention of this visuomotor update impairs post-exposure performance relative to the pre-exposure baseline. Although adaptation has previously been explored in response to constant delays, there has been no investigation into how continuously varying delays affect adaptation. In this experiment, participants completed a mouse-based target acquisition task with either a constant or varying delay between the mouse and cursor movements. At first exposure to the delays, completion times were large, and both delay conditions frequently overshot the target. With repeated exposure, the precision of the movements improved, resulting in lower completion times and fewer overshoots. The constant and varying delay conditions showed similar rates of change throughout the exposure phase, suggesting similar adaptation rates. Following the removal of the delay, the two delay conditions demonstrated similar post-exposure after-effects, as they systematically undershot the target and showed a decrease in overshooting relative to the pre-exposure baseline. Despite delay variability imposing an unstable error signal between the expected and actual cursor locations, this did not disrupt adaptation. These results suggest that the participants in the varying delay condition adapted to the mean delay and that the fluctuations away from this value did not disrupt the generation of the visuomotor updates.