Research

Understanding the neural mechanisms of motor coordination in neurologically intact individuals and stroke survivors

Stroke is a leading cause of long-term disability in the U.S. and internationally. Deficits most evident in the limb contralateral to the side of the stroke involve muscle weakness, abnormal muscle tone, and impairment of muscular coordination. Among these three abnormalities, spasticity and muscle weakness have been the most extensively studied. Clinical descriptions of multi-joint, stereotypic movement of the impaired arm characterize the early stages of recovery following stroke into limb “muscle synergies”, broadly defined as either flexor or extensor type. The limb synergies indicate a deficit in intersegmental coordination after stroke. In many patients, impaired coordination exists and is severe even after the muscle weakness and tone are treated or spontaneously resolved. Accordingly, abnormal movement coordination is likely to be the primary source of global movement dysfunction that significantly limits the ability to perform reaching movements in many hemiparetic stroke survivors.

We are attempting to help rehabilitation of stroke survivors’ arm motor skill function by learning how stroke causes changes in muscle coordination and how the brain activates arm muscles. Once we better understand these processes, the scientific results will provide clearer insights for physicians and therapists to better accommodate individual differences in movement execution and facilitate more personalized rehabilitation.

Developing novel rehabilitation strategies by using neural and muscular feedback

Stroke survivors often cannot individually move their elbow and shoulder joints in their everyday movement. One of the limitations of current stroke rehab protocols is to focus on overall motor functions (ex. movement speed) instead of more task-specific impairment in motor coordination. Our previous studies show certain groups of muscles are abnormally and consistently activated together under isometric conditions post-stroke which causes key motor performance problems. Isometric tasks are advantageous and accessible for stroke patients, especially with severe impairment, who need rehabilitative therapies the most but often do not receive appropriate treatment. We attempt to find novel, specific clinical targets for the post-stroke rehab, and create a new, therapeutic isometric approach.
The potential impact of this work will provide a scientific rationale and feasibility to develop a new, isometric muscle co-activation de-coupling approach for stroke rehabilitation and physical therapy. This will result in more healing and longer, healthier lives, more free of post-stroke motor impairment.