Abstract
BackgroundDeficits of kinesthesia (limb position and movement sensation) commonly limit sensorimotor function and its recovery after neuromotor injury. Sensory substitution technologies providing synthetic kinesthetic feedback might re-establish or enhance closed-loop control of goal-directed behaviors in people with impaired kinesthesia.MethodsAs a first step toward this goal, we evaluated the ability of unimpaired people to use vibrotactile sensory substitution to enhance stabilization and reaching tasks. Through two experiments, we compared the objective and subjective utility of two forms of supplemental feedback – limb state information or hand position error – to eliminate hand position drift, which develops naturally during stabilization tasks after removing visual feedback.ResultsExperiment 1 optimized the encoding of limb state feedback; the best form included hand position and velocity information, but was weighted much more heavily toward position feedback. Upon comparing optimal limb state feedback vs. hand position error feedback in Experiment 2, we found both encoding schemes capable of enhancing stabilization and reach performance in the absence of vision. However, error encoding yielded superior outcomes - objective and subjective - due to the additional task-relevant information it contains.ConclusionsThe results of this study have established the immediate utility and relative merits of two forms of vibrotactile kinesthetic feedback in enhancing stabilization and reaching actions performed with the arm and hand in neurotypical people. These findings can guide future development of vibrotactile sensory substitution technologies for improving sensorimotor function after neuromotor injury in survivors who retain motor capacity, but lack proprioceptive integrity in their more affected arm.
Highlights
Deficits of kinesthesia commonly limit sensorimotor function and its recovery after neuromotor injury
In a first set of experiments, we evaluated different weighted combination of moving hand position and velocity information to find the form of supplemental state feedback that minimizes performance error during stabilization and reaching tasks performed with the arm
We focused our analysis of population behavior on RMSEdrift during the posttraining baseline (V−T−) testing (V−T+) and sham feedback (V−TSHAM) phases of this Experiment (Fig. 2c)
Summary
Deficits of kinesthesia (limb position and movement sensation) commonly limit sensorimotor function and its recovery after neuromotor injury. The current study tested the ability of people with no known neuromotor deficits to control goal-directed actions using supplemental vibrotactile stimuli that provided real-time feedback about the moving limb to a part of the body that was not itself involved either in the movement or in essential behaviors like speaking and eating. We justify this approach by noting that the vast majority of people – including neurologically intact individuals - exhibit imperfect somatosensory control of the arm and hand in the absence of ongoing visual feedback. Proprioceptive drift succinctly predicts the pattern of performance errors observed during goaldirected reaching [43] and stabilizing actions [53] performed with the hand in the absence of visual feedback
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