ABSTRACT
A unique property of living motor control systems is the ability to rapidly modify behavior in a changing environment. This study addressed this phenomenon by investigating how human subjects attain the same final wrist position under varying load conditions. Subjects trained to make fast flexion movements with no load to a target. After that, they repeated the same movements (like-training trials) but in random trials (test trials), movements were either opposed or assisted by a load generated by linear position feedback to a torque motor. In two other experiments, subjects initially trained to reach the target with opposing or assisting loads respectively, while on random test trials, the load was not presented. Subjects were instructed to correct their positional errors as soon as possible.
