The Effects of Stochastic Galvanic Vestibular Stimulation on Body Sway and Muscle Activity

Abstract

Objective: This study aimed to investigate whether galvanic vestibular stimulation with stochastic noise (nGVS) modulates the body sway and muscle activity of the lower limbs, depending on visual and somatosensory information from the foot using rubber-foam.Methods: Seventeen healthy young adults participated in the study. Each subject maintained an upright standing position on a force plate with/without rubber-foam, with their eyes open/closed, to measure the position of their foot center of pressure. Thirty minutes after baseline measurements under four possible conditions (eyes open/closed with/without rubber-foam) performed without nGVS (intensity: 1 mA, duration: 40 s), the stimulation trials (sham-nGVS/real-nGVS) were conducted under the same conditions in random order, which were then repeated a week or more later. The total center of pressure (COP) path length movement (COP-TL) and COP movement velocity in the mediolateral (Vel-ML) and anteroposterior (Vel-AP) directions were recorded for 30 s during nGVS. Furthermore, electromyography activity of the right tibial anterior muscle and soleus muscle was recorded for the same time and analyzed.Results: Three-way analysis of variance and post-hoc multiple comparison revealed a significant increment in COP-related parameters by nGVS, and a significant increment in soleus muscle activity on rubber. There was no significant effect of eye condition on any parameter.Conclusions: During nGVS (1 mA), body sway and muscle activity in the lower limb may be increased depending not on the visual condition, but on the foot somatosensory condition.

Vestibulo-Ocular Reflex Is Modulated by Noisy Galvanic Vestibular Stimulation

“…A previous study reported that nGVS at 0.2 mA decreased body sway in patients with vestibular disorder, while that at 0.5 mA increased body sway (20). Another previous study similarly reported that nGVS at 1 mA increased the COP-TL in a healthy young population (19). Therefore, our finding that nGVS at 0.6 mA increases COP-TL is consistent with those of previous studies.…”

“…A possible mechanism for this alteration is interference by nGVS in vestibular information carried by the irregular vestibular neurons originating from Type I Hair Cells ( 16 ). Although nGVS is thought to alter the degree of vestibulospinal reflexes and body sway in both patients with vestibular disease ( 17 ) and healthy participants ( 18 , 19 ), it remains unclear whether nGVS alters the VOR. In the present study, therefore, we investigated whether nGVS induces changes in VOR-gain.…”

No Impact of Stochastic Galvanic Vestibular Stimulation on Arterial Pressure and Heart Rate Variability in the Elderly Population

“…A square-wave pulse GVS of 3 mA for 200 ms with an electrode over the bilateral mastoid process, similar to that in this study, did not induce pain ( Matsugi et al, 2017 ; Okada et al, 2018 ), and continuous direct current GVS of 1 mA induced a slight sensation in about 25% of young adult participants ( Nakamura et al, 2020 ). On the contrary, nGVS of 1 mA intensity using the same stimulator as in our study did not induce pain in 30 young adults in a static prone position ( Matsugi et al, 2020a ) and 17 young adults in a static standing position ( Matsugi et al, 2020b ). Therefore, an intensity of 0.4 mA for nGVS might be below the threshold of sensation, and based on these findings, we believe that nGVS at 0.4 mA cannot induce pain in the elderly population.…”

“…In the vestibular system, a particular level of mechanical noise on the semicircular canals can improve the performance of the vestibular system in peripheral sensory processing ( Flores et al, 2016 ). nGVS-induced modulation of the threshold of the vestibulospinal response ( Matsugi et al, 2020a ) is thought to contribute to body sway changes ( Matsugi et al, 2020b ; Sprenger et al, 2020 ). The vestibular system contributes to autonomic regulation ( Yates et al, 2014 ; McCall et al, 2017 ); therefore, nGVS might modulate AP and HR variability.…”

“…nGVS was performed as previously reported ( Matsugi et al, 2020a , b ). nGVS was delivered via Ag/AgCl surface electrodes (Blue Sensor EKG Snap Electrode, overall dimensions: 48 × 57 mm, Ambu, Baltorpbakken, Denmark) affixed to the right and left mastoid processes.…”