For 15 minutes every weekday, participants practice moving their wrist back and forth to make a cursor on the computer screen follow a target. Activity of the arm muscles is monitored with surface electrodes taped to the skin. The sessions continue until the participant can perform the movement well. Group 1 participants return to the clinic a week after the last session to perform the movement again to see if their skill level has changed. Each session lasts about 20 to 30 minutes.