Figure 1.

Experimental setup and procedures. (A) Subjects sat in a moveable chair with their forearm pronated and fixed in a splint rigidly coupled to a force transducer. A flat monitor occluded the subject's hand and displayed a virtual scene co-located with the real desktop. (B) Screenshot of the virtual scene. Subjects controlled the position of the blue sphere by applying forces to the force transducer. The sphere is illustrated inside the yellow semi-opaque sphere indicating the start position. The target is shown as a gray sphere. (C) Sequence of events in a trial. Subjects had to maintain the blue sphere inside the start sphere for 1 s. Afterwards the target appeared and the start sphere disappeared instructing the subject to reach it and to hold the blue sphere inside the target sphere for 1 s. The target sphere changed its color from gray to yellow when the target was reached. Finally, the subject was instructed to return to the start position and remain there for 1 s. (D) Organization of an experimental session. In the first block the maximum voluntary contraction (MVC) during generation of maximum voluntary force across directions was established followed by three baseline blocks, each consisting of 32 trials. From the fifth block to the tenth block a clockwise (CW) visuomotor rotation was introduced followed by three washout blocks without visuomotor rotation.