Two hands, one goal: Functional coupling in the wrist joints during a bimanual task

Bimanual coordination is essential for the performance of daily activities, but the underlying motor control mechanisms are not yet fully understood. The goal of the present study is to identify the contribution of contralateral responses in the wrist joints to the performance of a bimanual task. Contralateral responses could possibly be used in rehabilitation therapy to activate hand functions that are affected by a neuromuscular medical condition. In our experiment, participants had to balance a tray in a virtual environment, while either the left or right hand was perturbed. Two identical robotic wrist manipulators intermittently applied force perturbations in flexion or extension direction. Following a perturbation, contralateral responses were present and operated towards stabilization of the tray, for example by allowing an overall faster correction of the perturbation. Notably, flexion perturbations resulted in much larger contralateral responses than extension perturbations. Contralateral responses occurred mainly in the time window for voluntary responses. Results were consistent with our hypothesis for discrete bimanual movements based on optimal feedback control theory: when both hands share one goal, functional coupling occurs in the wrist joints.Biomedical Engineerin