 Hemiparesis is the most common motor impairment after stroke. Persistent deficits in the distal upper extremity lead to impaired hand function and disability in Activities of Daily Living, accruing enormous costs in terms of health care services and lost productivity. The mechanisms of recovery of hand motor function after stroke are poorly understood, and the protocols used in clinical practice lack a solid scientific rationale. Prior work has shown that grasping with the non-involved hand may assist in planning of grasp with the involved hand after stroke. The goal of the proposed project is to investigate the type and nature of information relayed across the hemispheres by prior manipulation with the non-involved hand to improve planning and control of grasp with the involved hand. Psychophysical methods using a grip instrument will be used to examine the type of information necessary for planning of grasp, and quantitative surface electromyography will be used to investigate the contribution of improved planning to neuromuscular control of grasp. Integration of these methods in the study of grasp control will clarify the neural mechanisms underlying hand dysfunction, and facilitate the development of rational therapeutic protocols for upper extremity rehabilitation after stroke. 