Self-initiated feedback enhances reward positivity during motor learning in a standing weight-shifting task.

Background/Objectives: In motor learning, post-trial feedback provides critical information for interpreting action outcomes and adjusting subsequent motor output. One factor that may influence how feedback is processed is agency. Methods: Thirty-two healthy young adults performed a standing weight-shifting task in which they reached targets without an online center of pressure (COP) display. Feedback was displayed using colors and arrows. We compared self-initiated feedback (sFB), which participants obtained by pressing a button, with externally provided feedback (eFB), which was delivered by the experimenter. Electroencephalography (EEG) data were analyzed using a counterbalanced within-subject crossover design to compare feedback-related neural responses between conditions. Because the same task was performed in both phases, motor performance was compared between groups using data from the first phase only in order to avoid carryover effects. Reward positivity (RewP) was measured as a neural indicator of reward processing. Motor performance was evaluated as the distance error between the maximal COP position and the target location. Results: RewP was significantly larger in the sFB condition than in the eFB condition, suggesting enhanced reward processing under self-initiated feedback. During the training sessions, distance error decreased in both groups, indicating a learning effect. In the post-training test sessions, a significant main effect of group was observed. Exploratory Conclusion: In a standing weight-shifting task, self-initiated feedback enhanced RewP amplitude, which reflects reward processing, and improved retention of postural control ability. These findings suggest that obtaining feedback with a sense of agency influences neural reward processing and the retention of motor learning effects.