Development of sensory augmentation methods to improve post-stroke gait stability

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Following a stroke, deficits in independent mobility are a primary contributor to decreased quality of life. Many stroke survivors, including the approximately 15,000 American veterans who experience a stroke each year, are prevented from returning to their prior levels of activity participation or involvement in the community. A major cause of mobility deficits is gait instability, which can result in an increased risk of falls or an increased fear of falling, either of which can limit independent function. While several common rehabilitation methods (e.g. locomotor training, strengthening, balance training) can improve some aspects of function, they have failed to address gait instability, as evidenced by a lack of improvement in fall incidence. In part, this lack of success is likely due to current interventions not being targeted toward the specific mechanisms causing post- stroke gait instability. A long-term goal of this research is to develop mechanism-based interventions that can improve post-stroke gait stability and be implemented in the clinic or community. As a step toward this goal, this project focuses on one promising potential mechanistic cause of post-stroke gait instability. Specifically, post-stroke deficits in the mechanically-appropriate step-by-step adjustments of step width will be targeted. The central hypothesis of this work is that augmented sensory feedback will increase the mechanics-dependent modulation of step width, an important gait stabilization strategy that is often disrupted in chronic stroke survivors. Promisingly, non-invasive sensory stimulation has been shown to shape an individual’s perception of the motion of their pelvis during walking, thus influencing their step-by-step control. The objective of this proposal is to develop and test a method of providing real-time augmentation of hip proprioceptive feedback through vibratory stimuli delivered using tactors during post-stroke walking. This will be accomplished through three Specific Aims. The first Specific Aim is to identify the physiological mechanism underlying the beneficial effects of sensory augmentation on step-by-step gait stabilization. Beyond being of scientific interest, the results will provide insight into the mechanism that should be targeted for the future development of a portable device to be used in the clinic or community. The second Specific Aim is to determine whether personalizing sensory augmentation methods to individual participants produces greater beneficial effects on post-stroke gait stability, which will allow us to account for potential variation in patient responsiveness to sensory stimulation. Finally, the third Specific Aim is to establish the safety, feasibility, and efficacy of a rehabilitation intervention centered on repeated exposure to sensory augmentation during gait. The results will provide justification for a future larger-scale clinical trial. Overall, the results of the proposed work will form the foundation for the development of a novel rehabilitation device that can assist gait balance outside of a research laboratory setting. The proposed project is based on the combined theoretical frameworks of human gait mechanics and motor learning, and will quantify the potential of a mechanism-based intervention using novel sensory stimulation to restore the typical gait stabilization strategy in stroke survivors. The resultant knowledge has the potential to make an important contribution to the development of a larger-scale rehabilitation paradigm in which therapeutic interventions are targeted to a patient’s specific limitations.