Abstract
It has recently been demonstrated that noisy galvanic vestibular stimulation (nGVS) delivered as imperceptible white noise can improve balance control via the induction of stochastic resonance. However, it is unclear whether these balance improvements are accompanied by simultaneous enhancement to vestibular motion perception. In this study, 15 healthy subjects performed 8 quiet-stance tasks on foam with eyes closed at 8 different nGVS amplitudes ranging from 0 mA (baseline) to 0.5 mA. The nGVS amplitude that improved balance performance most compared to baseline was assigned as the optimal nGVS amplitude. Optimal nGVS amplitudes could be determined for 13 out of 15 subjects, who were included in the subsequent experimental procedures. The effect of nGVS delivered at the determined optimal intensity on vestibular perceptual thresholds was examined using direction-recognition tasks on a motion platform, testing roll rotations at 0.2, 0.5, and 1.0 Hz, both with active and sham nGVS stimulations. nGVS significantly reduced direction-recognition thresholds compared to the sham condition at 0.5 and 1.0 Hz, while no significant effect of nGVS was found at 0.2 Hz. Interestingly, no correlation was found between nGVS-induced improvements in balance control and vestibular motion perception at 0.5 and 1 Hz, which may suggest different mechanisms by which nGVS affects both modalities. For the first time, we show that nGVS can enhance roll vestibular motion perception. The outcomes of this study are likely to be relevant for the potential therapeutic use of nGVS in patients with balance problems.
Highlights
It is commonly thought that the presence of noise in sensory systems has detrimental effects on the system’s ability to detect and process incoming signals
Analysis for individual frequencies revealed reduced motion perception thresholds in the noisy galvanic vestibular stimulation (nGVS) condition compared to the sham condition for the 1 Hz roll motion (F1,12 = 8.455, p = 0.013; 0.56 vs. 0.76 deg/s, respectively; mean threshold reduction: 20.1 ± 0.5%)
We show that nGVS improves stance performance in a static posturography paradigm, and influences vestibular perception in roll during a motion recognition task
Summary
It is commonly thought that the presence of noise in sensory systems has detrimental effects on the system’s ability to detect and process incoming signals. There is, growing evidence that under certain conditions an appropriate amount of noise can improve the signal-to-noise ratio in nonlinear systems and thereby enhance the recognition and transmission of the incoming information flow [1, 2]. This phenomenon is based on a mechanism known as stochastic resonance (SR) in which the response of a nonlinear system to weak input signals can be optimized by the presence of a particular non-zero level of stochastic interference, i.e., noise [3]. External noise stimulation in these systems yields an improved processing of weak, sub-threshold stimuli, and thereby effectively lowers the system’s recognition threshold.
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