Use-Dependent and Error-Based Learning of Motor Behaviors

TLDR

Human motor behavior is continuously reshaped by error‑based learning, whereby encountering a movement error triggers an updated internal model that immediately adjusts subsequent movements to counteract the perturbation. This study demonstrates that a second, use‑dependent learning mechanism concurrently alters movements to resemble the most recent movement. Three experiments manipulated reaching movements toward a horizontally elongated target; by passively guiding movements 8° from the previous direction and by physically constraining active movements, the authors induced use‑dependent learning and revealed that error‑based and use‑dependent learning can operate simultaneously in opposing directions. When the constraint was removed, participants first showed a brief error‑based aftereffect opposite the constraint direction, then a longer‑lasting use‑dependent aftereffect toward the constraint direction, and the combined action of both mechanisms determined the motor solution adopted during task learning.

Abstract

Human motor behavior is constantly adapted through the process of error-based learning. When the motor 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 elongated 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 guiding movements 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 active movements. After removal of the constraint, participants briefly exhibit an error-based aftereffect against the direction of the constraint, followed by 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.