Augmenting kinesthetic feedback to improve hemiparetic arm control after stroke

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Current research and clinical efforts related to post-stroke arm rehabilitation focus primarily on motor retraining, with limited focus on the impact of somatosensory deficits on motor function. This is not surprising given that arms are not very useful without volitional movement. However, somatosensory deficits are common in the contralesional arm and may contribute importantly to deficits in the control of functional movement. This project advances the goal of promoting functional motor recovery after stroke by creating "sensory substitution" technologies that re-establish kinesthetic feedback control of the contralesional arm by delivering augmented feedback to a body part for which the brain retains the ability to process somatosensory feedback. The objective of this application is to determine how best to synthesize and deliver supplemental kinesthetic feedback, and to test its ability to enhance sensorimotor control over the contralesional arm post-stroke. This study has two Aims. The first seeks to optimize delivery of supplemental kinesthetic feedback to enhance reach, stabilization and manipulation actions of the contralesional arm post-stroke. Several different vibrotactile feedback encodings of limb position and velocity will be synthesized and applied to sites on the body retaining somatosensation. The specific combination of state variables and stimulation site that best enhance stabilization and manipulation with the contralesional arm and hand will be identified in a small cohort of stroke survivors. This Aim tests the hypotheses that supplemental feedback including both position and velocity state information will best enhance arm control and best reduce abnormal coupling between hand grip force and arm stability. Aim 2, seeks to characterize learning that accrues due to extended training with supplemental kinesthetic feedback. Over a period of three weeks, a small cohort of stroke survivors will train to use supplemental kinesthetic feedback to enhance reach-to-grasp actions in a 3-dimensional environment. We test the hypothesis that extended training with supplemental kinesthetic feedback leads to new compensatory skills that generalize to untrained action sequences that contribute to the success of many behaviors of daily living. Upon completion, this project will determine how best to synthesize and deliver supplemental sensory feedback to improve contralesional arm control in stroke survivors with residual motor capacity but impaired or absent proprioception in the contralesional arm. This contribution will be significant because it develops a new assistive technology with the potential to improve contralesional arm use in many stroke survivors. This proposal is innovative because it represents a substantive departure from the status quo, both in the field of physical rehabilitation after stroke and in the field of sensory substitution, by shifting the focus of motor retraining toward the re-establishment of real-time closed-loop feedback control of the contralesional arm. Successful completion of this project will ultimately lead to novel, continuously wearable technologies that will enable many stroke survivors to recover impaired or lost capabilities in the contralesional arm.