Subthreshold stochastic vestibular stimulation affects balance-challenged standing and walking

Abstract

Subthreshold stochastic vestibular stimulation (SVS) is thought to enhance vestibular sensitivity and improve balance. However, it is unclear how SVS affects standing and walking when balance is challenged, particularly when the eyes are open. It is also unclear how different methods to determine stimulation intensity influence the effects. We aimed to determine (1) whether SVS affects stability when balance is challenged during eyes-open standing and overground walking tasks, and (2) how the effects differ based on whether optimal stimulation amplitude is derived from sinusoidal or cutaneous threshold techniques. Thirteen healthy adults performed balance-unchallenged and balance-challenged standing and walking tasks with SVS (0-30 Hz zero-mean, white noise electrical stimulus) or sham stimulation. For the balance-challenged condition, participants had inflatable rubber hemispheres attached to the bottom of their shoes to reduce the control provided by moving the center of pressure under their base of support. In different blocks of trials, we set SVS intensity to either 50% of participants' sinusoidal (motion) threshold or 80% of participants' cutaneous threshold. SVS reduced medial-lateral trunk velocity root mean square in the balance-challenged (p < 0.05) but not in the balance-unchallenged condition during standing. Regardless of condition, SVS decreased step-width variability and marginally increased gait speed when walking with the eyes open (p < 0.05). SVS intensity had minimal effect on the standing and walking measures. Taken together, our results provide insight into the effectiveness of SVS at improving balance-challenged, eyes-open standing and walking performance in healthy adults. OPEN ACCESSCitation: Piccolo C, Bakkum A, Marigold DS (2020) Subthreshold stochastic vestibular stimulation affects balance-challenged standing and walking. PLoS ONE 15(4): e0231334. https://doi.org/ 10.

Efficacy of nGVS to improve postural stability in people with bilateral vestibulopathy: A systematic review and meta-analysis

“…Iwasaki et al ( 2018 ) found that nGVS increased gait speed and stride length, and decreased stride time, in people with BVP during overground walking. A similar effect was found in healthy young people during overground walking and walking on unsteady surfaces (Piccolo et al, 2020 ). To the contrary, Wuehr et al ( 2016a , b ) found there was no change in spatiotemporal gait parameters in healthy or BVP populations during walking at slow, preferred, and fast speeds.…”

“…This finding is noteworthy, as lateral gait variance has been cited as a defining feature of gait imbalance in people with BVP (Schniepp et al, 2019 ). Decreased step width variability (Wuehr et al, 2016b ; Piccolo et al, 2020 ) and improved stability during lateral perturbation of the support surface (Mulavara et al, 2015 ) have also been found in nGVS studies on young healthy people, strengthening support for the role of nGVS to augment vestibular afferents and maintain stable gait (Schniepp et al, 2019 ).…”

Cortical Effects of Noisy Galvanic Vestibular Stimulation Using Functional Near-Infrared Spectroscopy

“…This is an important first step toward more widespread use of this technology when applying nGVS. Sixth, our noisy stimulation parameters matched several studies [ 9 , 10 , 38 ] but differed from many others [ 4 , 5 , 7 , 8 , 17 ]. How different noisy stimulation parameters influence HbO and HbR concentrations is unclear at this time.…”

“…If they could not, we increased the current by another step. Once participants reported feeling the stimulation, we set the signal to 80% of this current value [ 5 , 8 , 17 ]. Subsequently, we confirmed that participants did not feel the current (average peak current: 183 +/− 95 µA), which we delivered as the stimulation magnitude for the experimental session.…”

“…This stimulation activates both vestibular hair cells and afferents of the otoliths and semicircular canals [ 1 , 2 ]. nGVS can improve standing balance [ 3 , 4 , 5 ], walking [ 5 , 6 , 7 , 8 ], upper-limb function [ 9 , 10 ], vestibular-ocular function [ 11 , 12 ], sensory perception [ 13 , 14 ], memory [ 15 ], and visuospatial navigation [ 16 ]. The improvements in motor function are also evident in clinical populations, such as those with bilateral vestibulopathy [ 3 , 17 ].…”