Background: Current neuroscience has identified rehabilitation approaches with the potential to stimulate adaptive changes in the brains of persons with hemiparesis. These approaches include, intensive task-oriented training, bimanual activities and balancing proximal and distal upper extremity interventions to reduce competition between these segments for neural territory.

Current neuroscience has identified several constructs to increase the effectiveness of upper extremity rehabilitation. One is the use of progressive, skill acquisition-oriented training. Another approach emphasizes the use of bilateral activities. Building on these principles, this paper describes the design and feasibility testing of a robotic / virtual environment system designed to train the arm of persons who have had strokes. The system provides a variety of assistance modes, scalable workspaces and hand-robot interfaces allowing persons with strokes to train multiple joints in three dimensions. The simulations utilize assistance algorithms that adjust task difficulty both online and offline in relation to subject performance. Several distinctive haptic effects have been incorporated into the simulations. An adaptive master-slave relationship between the unimpaired and impaired arm encourages active movement of the subject's hemiparetic arm during a bimanual task. Adaptive anti-gravity support and damping stabilize the arm during virtual reaching and placement tasks. An adaptive virtual spring provides assistance to complete the movement if the subject is unable to complete the task in time. Finally, haptically rendered virtual objects help to shape the movement trajectory during a virtual placement task. A proof of concept study demonstrated this system to be safe, feasible and worthy of further study.

This study describes a novel robotic system using haptic effects and objects, in rich, three- dimensional virtual environments (VEs) for the sensorimotor training of the hemiparetic hand. This system is used to compare effectiveness of two training paradigms, one using activities that train the hand and arm together (HAT) as a functional unit to training the hand and arm in similar conditions, separately (HAS). Four subjects practiced three hours/day for 8 days using (HAS) robotic simulations. Four subjects practiced same amount of time using HAT simulations. HAT group improved 23% in the Wolf Motor Function Test and 29% in the Jebsen Test of Hand Function, whereas HAS group only improved 14% and 8%. HAT group also demonstrated larger decreases in hand trajectory length in the VE-based training that involved reaching and object placing, indicating improved limb segment coordination, (40% HAT; 19% HAS). Both groups improved the smoothness of robotically measured hand trajectories 56%, suggesting improved motor control. During virtual piano training, subjects showed similar improvements in key press accuracy (17% HAT; 20% HAS) however, the HAT group demonstrated larger improvements in average time needed to press a key (151% HAT; 60% HAS). Our initial findings suggest that training the arm and hand as a unit following stroke may be more effective for improving upper extremity function than training the hand and arm in isolation.

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