Cerebral contribution to the execution, but not recalibration, of motor commands in a novel walking environment.

Abstract

Human movements are flexible as they continuously adapt to changes in the environment by updating planned actions and generating corrective movements. Planned actions are updated upon repeated exposure to predictable changes in the environment, whereas corrective responses serve to overcome unexpected environmental transitions. It has been shown that corrective muscle responses are tuned through sensorimotor adaptation induced by persistent exposure to a novel situation. Here, we asked whether cerebral structures contribute to this recalibration using stroke as a disease model. To this end, we characterized changes in muscle activity in stroke survivors and unimpaired individuals before, during, and after walking on a split-belt treadmill moving the legs at different speeds, which has been shown to induce recalibration of corrective responses in walking in healthy individuals. We found that the recalibration of corrective muscle activity was comparable between stroke survivors and controls, which was surprising given then known deficits in feedback responses post-stroke. Also, the intact recalibration in the group of stroke survivors contrasted the patients limited ability to adjust their muscle activity during steady state split-belt walking compared to controls. Our results suggest that the recalibration and execution of motor commands in new environments are partially dissociable: cerebral lesions interfere with the execution, but not the recalibration, of motor commands upon novel movement demands.