Implicit contributions to dual visuomotor adaptation.

The ability to seamlessly switch between different visuomotor mappings is critical for effective interactions in a dynamic environment. This experiment aimed to establish the contributions of implicit (unconscious) processes to the concurrent adaptation of one's reaches to two opposing, randomly switching, novel visuomotor mappings (i.e., dual visuomotor adaptation). 59 right-handed participants were divided into two groups, a Dual adaptation group and a Single adaptation group, and trained to reach when small visuomotor distortions were introduced. The Dual group trained to reach when cursor feedback was rotated (i) 20° clockwise (CW) relative to hand motion when a target was displayed in the left visual workspace and (ii) 20° counterclockwise (CCW) relative to hand motion when a target was displayed in the right visual workspace. The Single group trained to reach with just one 20° cursor rotation (CW or CCW) in both visual workspaces. Results revealed that all participants adapted their reaches to the distorted cursor feedback. For all groups, visuomotor adaptation arose implicitly, in the absence of explicit (conscious strategy) contributions. However, the Dual group demonstrated significantly less implicit adaptation than participants who trained with a Single CW distortion, even after additional reach training trials. Together, these results indicate a role for implicit processes in simultaneously updating one's reaches to two small visuomotor mappings.