Utility and User Experience with 3-Dimensional Vibrotactile Kinesthetic Feedback for Improving Reach-to-Grasp Accuracy and Efficiency After Stroke: A Case Series.

Recent studies have shown that supplemental sensory feedback systems have potential to mitigate functional impairment after neuromotor injury through mechanisms of sensory augmentation or replacement. In this proof-of-concept case series, we evaluated multi-session 3-dimensional kinesthetic vibrotactile feedback training as a means to enhance the accuracy and efficiency of goal-directed reaching in the absence of visual feedback in survivors of stroke. A motion capture system converted real-time position of the contralesional hand within a Cartesian frame of reference into spatiotemporal patterns of vibrotactile feedback provided to the non-moving, ipsilesional arm. Seven survivors of stroke underwent 9 hours of reach-to-grasp training under conditions that encouraged them to learn a mapping from hand position to patterns of vibrotactile feedback. We then assessed their ability to use that feedback to improve the accuracy and efficiency of reaches performed without concurrent visual feedback. Within-subject comparisons to baseline performance revealed heterogeneous learning effects on reaching both with and without supplemental vibrotactile feedback. When reaching with the supplemental feedback after training, three participants significantly improved reach accuracy, two significantly improved temporal efficiency, and three significantly improved spatial efficiency (although one significantly worsened with regard to spatial efficiency). Further, all but one of the participants who exhibited post-training performance changes during movements made with the supplemental feedback also exhibited similar post-training performance changes during movements made without the supplemental feedback. These results suggest that while a subset of stroke survivors may accrue benefits from using the form of supplemental vibrotactile kinesthetic feedback described in the paper, the effects of such training resulted primarily from ancillary benefits provided by the 9 hours of intensive reach-to-grasp training with the feedback, rather than from the ongoing use of the feedback itself. Despite the mixed kinematic results, responses to standard surveys of subjective experience suggest that training with the vibrotactile display had acceptable usability and was both motivating and satisfying to use. We conclude that while the wearable technology may provide a positive user experience, practical benefits (e.g., increased reach accuracy or efficiency) may accrue more from hours of focused reach training than from the additional sensory information provided by the vibrotactile interface. (National Clinical Trial Number: NCT03298243; clinicaltrials.gov/study/NCT03298243).