Multi-Joint Sensorimotor Dysfunction of the Stroke Arm

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The purpose of this research partnership is to investigate the functional implications of using sensor feedback to enhance motor control of the arm post-stroke. Two key functional aspects of motor control of the arm will be examined: 1) Reach, which involves coordinated actions of the shoulder and elbow musculature and 2) grasp, which incorporates both finger position and force controls. For each system, we will demonstrate that sensory feedback from nonhomologous joints has a significant effect on motor control. Initially, we will examine the intralimb reflex coupling of wrist/hand sensory feedback on elbow and shoulder musculature and visa versa. For Aim 1 of this study, we will show that motorized stretch of the elbow and fingers produces reflex activity in muscles that are not perturbed. These effects will be compared between post-stroke and neurologically intact individuals using tendon tap perturbations. Sensory manipulations consisting of posture electrical stimulation, vibration and anesthesia will be used to modify the heteronymous reflex responses. Having demonstrated reflex coupling across joints, we will then examine the effects that this reflex coupling may have on motor function. In Aim 2, motor control tasks of the upper arm (e.g. reach) will be tested during sensory manipulations of the fingers and wrist. Similarly, motor tasks of the hand will be tested with modifications of sensory inputs to the elbow and shoulder. These studies will demonstrate that sensory signals from nonhomologous joints can substantialy enhance motor function. The results of this study will suggest a new type of approach for rehabilitation of arm function post-stroke. We postulate that substantial improvements in arm function can be achieved by developing new technologies that provide artificial sensory feedback. In addition, conventional therapies may be applied more efficiently or effectively using the principles that will be demonstrated by this study.