Figure 1.

Experimental setup and design. Volunteers performed a complex ball-rotation task with two cork balls. (A) Volunteers in MVF_DH rotated the balls with their non-dominant hand (NDH) in a counterclockwise direction for 1 min (untrained hand pre), followed by a 15 min training period with the dominant hand (DH) in a clockwise direction while mirror visual feedback (MVF) was provided (10 trials of 1 min each with 30 s break in between). After the training phase, the performance of the NDH was retested (untrained hand post). (B) Volunteers in MVF_NDH received the same instructions and conducted the same task just vice versa: MVF-training was performed with the NDH while the DH was assessed before and after MVF (untrained hand pre and post). In both groups, volunteers rotated the balls with the NDH always in a counterclockwise direction and with the DH always in a clockwise direction. (C) During the task, volunteers in both groups were seated in a comfortable chair with their elbows flexed at 90° and with their pronated hands rested on a desk in front of them. While MVF was provided, a mirror was placed in the subject’s midsagittalplane and the performing hand was covered by a wooden barrier to prevent direct view. See text for details.