Fast Corrective Responses in Redundant Motor Control Are Shaped by Intrinsic Constraints of Movement Patterns

In real-world motor tasks, body movements unfold in a high-dimensional space, whereas task errors are defined in a lower-dimensional space. How such low-dimensional errors propagate across redundant motor degrees of freedom to generate rapid corrective responses remains poorly understood. To address this question, we developed a redundant bimanual task in which human participants (males and females) manipulated a virtual stick with both hands to move its tip to a visual target. By shifting the tip position (task-relevant perturbation) or rotating the stick with the tip position fixed (task-irrelevant perturbation), we separated task-space errors from redundant-dimension errors. Participants rapidly corrected both types of perturbations using highly stereotyped movement patterns. Corrections to task-relevant errors consistently involved coordinated changes across redundant dimensions, and even perturbations that did not affect task success elicited systematic corrective responses. Together, these results demonstrate that fast corrective responses in redundant motor control are shaped by intrinsic coordination constraints that govern how visual errors propagate through the motor system.