Behavioral/Systems/Cognitive Use-Dependent and Error-Based Learning of Motor Behaviors

Humanmotor behavior is constantly adapted through the process of error-based learning.When themotor system encounters an error, its estimate about the body and environment will change, and the next movement will be immediately modified to counteract the underlying perturbation. Here, we show that a second mechanism, use-dependent learning, simultaneously changes movements to become more similar to the last movement. In three experiments, participants made reaching movements toward a horizontally elon-gated target, such that errors in the initial movement direction did not have to be corrected. Along this task-redundant dimension, we were able to induce use-dependent learning by passively guidingmovements in a direction angled by 8 ° from the previous direction. In a second study, we show that error-based and use-dependent learning can change motor behavior simultaneously in opposing directions by physically constraining the direction of activemovements. After removal of the constraint, participants briefly exhibit an error-based aftereffect against the direction of the constraint, followedby a longer-lasting use-dependent aftereffect in the direction of the constraint. In the third experiment, we show that these two learning mechanisms together determine the solution the motor system adopts when learning a motor task