Abstract
After adapting to altered visual feedback of an unseen hand while reaching to visual targets, many studies have shown that the opposite hand also benefits when reaching with the same altered feedback, suggesting intermanual transfer. It is unclear why intermanual transfer occurs. Does transfer occur because the brain is learning new cursor mechanics, which are constant for each hand? If so, then we predict that bimanual transfer should occur when subjects learn to reach with a cursor representing their hand and not an image of their hand. Subjects reached to one of 10 radial targets with an unseen hand. One group of subjects reached with a rotated cursor representing their unseen right hand. Another group of subjects saw a rotated view of their right hand while they performed the same task: these movements were captured using a camera, and displayed in real time on a vertical screen. The motion of the cursor or the image of the hand was rotated either 45° or 105° CCW in the learning condition, where subjects reached for 200 trials with their right hand. Each learning session was followed by a test condition where subjects reached to the same targets under the same viewing condition but with the left, untrained hand for 30 trials. Reaching with the left hand in the cursor condition was significantly less deviated for the first 10 trials of testing compared to the first 10 trials of learning for the 45° rotation (p = .001) and the 105° rotation (p = .001), suggesting intermanual transfer when the cursor was seen. The rotated hand view condition showed no significant transfer for either rotation (p [[gt]] .05). Our results suggest that intermanual transfer may occur because an internal model of the cursor, rather than the arm motor system, is learned.