Preprint Article Version 1 This version is not peer-reviewed

Optimal Noise Level for Imperceptible Vibrotactile Stimulation during a Force Stability Task

Version 1 : Received: 19 November 2018 / Approved: 21 November 2018 / Online: 21 November 2018 (06:39:21 CET)

How to cite: Haynes, C.A.; Tenan, M.S..; Passaro, A.D..; Tweedell, A.J. Optimal Noise Level for Imperceptible Vibrotactile Stimulation during a Force Stability Task. Preprints 2018, 2018110516 (doi: 10.20944/preprints201811.0516.v1). Haynes, C.A.; Tenan, M.S..; Passaro, A.D..; Tweedell, A.J. Optimal Noise Level for Imperceptible Vibrotactile Stimulation during a Force Stability Task. Preprints 2018, 2018110516 (doi: 10.20944/preprints201811.0516.v1).

Abstract

Imperceptible vibratory noise stimulation has shown to be an effective means of improving stability for both whole body postural control and simple motor control tasks.  While the physiological mechanism affording this improvement is uncertain, it is suspected that sensory noise stimulation may elicit a stochastic resonance-like effect within the somatosensory system.  A stochastic resonance effect describes the phenomenon in which noise added to a non-linear system improves signal detection rather than degrading it.  One hallmark of stochastic resonance is the existence of an optimal noise level which elicits the best system performance.  There is disagreement in the literature regarding the presence of an optimal stimulation level for motor stability in humans.  The goals of this study were to: 1) determine optimal stimulation level as a function of an individual’s sub-sensory threshold level, and 2) to determine whether performance of a force stability task was significantly better when subjects received stimulation at this identified optimal level compared to other sub-sensory threshold stimulation levels.  Eighteen (18) participants completed an isometric finger flexion task with visual feedback while receiving noise stimulation scaled to varying percentages of their individual sub-sensory threshold level.  Performance for this force stabilization task was quantified as the root-mean-square (RMS) error between the target force and the actual generated force values.  Despite controlling all other signal properties and varying only amplitude, optimal noise stimulation values still varied widely across participants (10-100% sub-sensory threshold level).  Statistical modeling revealed a significant improvement in task performance with optimal noise stimulation compared to other sub-sensory stimulation levels (p ≤ 0.019) with estimated marginal mean differences in force errors ranging from 0.13 to 0.23 N.  Moderate significant Spearman correlations (rs = 0.49 and r= 0.56, respectively) were found between finger flexion maximal voluntary contraction (MVC) and sub-sensory threshold level and MVC and optimal stimulation level.  A strong, significant Spearman correlation (rs = 0.65) was observed between sub-sensory threshold level and optimal stimulation level.  Although these correlations do not provide a means to predict optimal stimulation level as a function of these other measures, optimal stimulation level appears to increase with sub-sensory threshold and MVC.

Subject Areas

imperceptible; stimulation; vibrotactile; Gaussian noise; stochastic resonance; somatosensory system; sub-sensory threshold

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