Designing Visual Feedback to Reshape Muscle Coordination

Dysfunctional muscle activations are observed after stroke and in other neurological disorders. We propose an approach to rehabilitation exercises based on conditioning the availability of visual feedback upon the attainment of an established pattern of muscle activation. As a proof of concept, we tested this approach on unimpaired participants who were asked to perform reaching arm movements while holding a robotic manipulandum. A cursor provided participants with visual feedback of their hand position. The cursor visibility was set in proportion to the RMS EMG activity of the triceps, varying from transparent to maximally visible within a range corresponding to the desired muscle activity level. The great majority of the subjects increased significantly the activity of the triceps as they practiced the reaching task however this returned to baseline at the end of training. We expect that changes can be retained after more intense training if they have functional relevance.