Noisy Galvanic Vestibular Stimulation Research Articles

Effect of Noisy Galvanic Vestibular Stimulation on Spatial Learning and Memory of Rats

Background and Aim: Previous studies have shown promising findings on effectiveness of noisy Galvanic Vestibular Stimulation (nGVS) in various cognitive disorders. The connections of the vestibular system with the hippocampus has been proven. Here we investigated the effect of vestibular galvanic stimulation on the improvement of spatial learning and memory of rats. Methods: Twelve Wistar rats were randomly divided into control and nGVS groups. The nGVS group underwent 30-minute sessions of stimulation at sub-threshold levels for a duration of fourteen days. Following the intervention, both groups underwent assessments of cognitive indices through the Morris water maze task, hippocampal neuronal spike rate by Single-Unit Recording (SUR) and the concentrations of c-fos protein in the hippocampus were measured using ELISA device. Results: The nGVS group exhibited a significant difference compared to the control group in both the time taken to reach the target platform and the percentage of time spent in the goal quarter during the Morris water maze test. The nGVS treatment significantly enhanced spike rate of hippocampal dentate gyrus (p<0.01) compared to the control group. Additionally, c-fos protein concentrations were increased in the nGVS (5.833) than the control group (4.126), (p<0.001). Conclusion: According to the obtained results, nGVS plays a role in improving spatial memory, and a longer duration of intervention is suggested to achieve more obvious improvement results. Keywords: Galvanic vestibular stimulation; spatial cognition; single-unit recording; hippocampus; rat

Low-intensity vestibular noise stimulation improves postural symptoms in progressive supranuclear palsy.

Postural imbalance and falls are an early disabling symptom in patients with progressive supranuclear palsy (PSP) of multifactorial origin that may involve abnormal vestibulospinal reflexes. Low-intensity noisy galvanic vestibular stimulation (nGVS) is a non-invasive treatment to normalize deficient vestibular function and attenuate imbalance in Parkinson's disease. The presumed therapeutic mode of nGVS is stochastic resonance (SR), a mechanism by which weak sensory noise stimulation can enhance sensory information processing. To examine potential treatment effects of nGVS on postural instability in 16 patients with PSP with a clinically probable and [18F]PI-2620 tau-PET-positive PSP. Effects of nGVS of varying intensity (0-0.7mA) on body sway were examined, while patients were standing with eyes closed on a posturographic force plate. We assumed a bell-shaped response curve with maximal sway reductions at intermediate nGVS intensities to be indicative of SR. An established SR-curve model was fitted on individual patient outcomes and three experienced human raters had to judge whether responses to nGVS were consistent with the exhibition of SR. We found nGVS-induced reductions of body sway compatible with SR in 9 patients (56%) with optimal improvements of 31 ± 10%. In eight patients (50%), nGVS-induced sway reductions exceeded the minimal clinically important difference (improvement: 34 ± 5%), indicative of strong SR. nGVS yielded clinically relevant reductions in body sway compatible with the exhibition of SR in vestibular sensorimotor pathways in at least half of the assessed patients. Non-invasive vestibular noise stimulation may be thus a well-tolerated treatment strategy to ameliorate postural symptoms in PSP.

Inter-day and intra-day variations in effective intensity of noisy galvanic vestibular stimulation to improve postural stability in bilateral vestibulopathy.

The reproducibility of the effective intensity of noisy galvanic vestibular stimulation (nGVS) to improve postural stability is not well known. We aimed to investigate inter-day and intra-day variations in effective intensity in patients with bilateral vestibulopathy (BVP). Thirteen BVP patients were measured for center-of-pressure movements in the standing posture at five time points: morning of the first test day, morning and evening of the second test day, and morning and evening of the third test day. The mean velocity, the envelopment area, and the root mean square were measured in the eyes-closed condition for 30 s during nGVS application ranging from 0 to 1000μA. The effective intensity was defined as the intensity at which all the three parameters measured during the stimulation were simultaneously smaller than the values at baseline (0μA). Seven of the 13 patients had a common effective intensity throughout the three test days. Six patients on the second test day and five patients on the third test day had no common effective intensity between morning and evening. The effective intensity of nGVS changes depending on the time during the day as well as between the days.

Mechanisms underlying treatment effects of vestibular noise stimulation on postural instability in patients with bilateral vestibulopathy.

Previous studies indicate that imbalance in patients with bilateral vestibulopathy (BVP) may be reduced by treatment with low-intensity noisy galvanic vestibular stimulation (nGVS). To elucidate the potential mechanisms underlying this therapeutic effect. In particular, we determined whether nGVS-induced balance improvements in patients are compatible with stochastic resonance (SR)-a mechanism by which weak noise stimulation can paradoxically enhance sensory signal processing. Effects of nGVS of varying intensities (0-0.7mA) on body sway were examined in 19 patients with BVP standing with eye closed on a posturographic force plate. We assumed a bell-shaped response curve with maximal sway reductions at intermediate nGVS intensities to be indicative of SR. An established SR curve model was fitted on individual patient outcomes, and three experienced human raters had to judge whether responses to nGVS were consistent with the exhibition of SR. nGVS-induced reductions of body sway compatible with SR were found in 12 patients (63%) with optimal improvements of 31 ± 21%. In 10 patients (53%), nGVS-induced sway reductions exceeded the minimally important clinical difference (optimal improvement: 35 ± 21%), indicative of strong SR. This beneficial effect was more likely in patients with severe vestibular loss (i.e. lower video head impulse test gain; R = 0.663; p = 0.002) and considerable postural imbalance (baseline body sway; R = 0.616; p = 0.005). More than half of the assessed patients showed robust improvements in postural balance compatible with SR when treated with nGVS. In particular, patients with a higher burden of disease may benefit from the non-invasive and well-tolerated treatment with nGVS.

Changes in vestibular-related responses to combined noisy galvanic vestibular stimulation and cerebellar transcranial direct current stimulation.

Vestibular nuclei and cerebellar function comprise vestibular neural networks that control vestibular-related responses. However, the vestibular-related responses to simultaneous stimulation of these regions are unclear. This study aimed to examine whether the combination of noisy galvanic vestibular stimulation (nGVS) and cerebellar transcranial direct current stimulation (ctDCS) using a complex transcranial electrical stimulation device alters vestibular-dominant standing stability and vestibulo-ocular reflex (VOR) function. The center of foot pressure (COP) sway and VOR of participants (28 healthy, young adults) were assessed under four conditions of transcranial electrical stimulation using nGVS and ctDCS. The COP was calculated with the participant standing on a soft-foam surface with eyes closed using a force plate to evaluate body sway. VOR measurements were collected via passive head movements and fixation on a target projected onto the front wall using a video head impulse test (vHIT). VOR gain was calculated in six directions using a semicircular canal structure based on the ratio of eye movement to head movement. The nGVS + ctDCS and nGVS + sham ctDCS conditions decreased COP sway compared to the sham nGVS + ctDCS and sham nGVS + sham ctDCS conditions. No significant differences were observed in the main effect of stimulation or the interaction of stimulation and direction on the vHIT parameters. The results of this study suggest that postural stability may be independently affected by nGVS. Our findings contribute to the basic neurological foundation for the clinical application of neurorehabilitation using transcranial electrical stimulation of the vestibular system.

Repetitive Low-Intensity Vestibular Noise Stimulation Partly Reverses Behavioral and Brain Activity Changes following Bilateral Vestibular Loss in Rats.

Low-intensity noisy galvanic vestibular stimulation (nGVS) can improve static and dynamic postural deficits in patients with bilateral vestibular loss (BVL). In this study, we aimed to explore the neurophysiological and neuroanatomical substrates underlying nGVS treatment effects in a rat model of BVL. Regional brain activation patterns and behavioral responses to a repeated 30 min nGVS treatment in comparison to sham stimulation were investigated by serial whole-brain 18F-FDG-PET measurements and quantitative locomotor assessments before and at nine consecutive time points up to 60 days after the chemical bilateral labyrinthectomy (BL). The 18F-FDG-PET revealed a broad nGVS-induced modulation on regional brain activation patterns encompassing biologically plausible brain networks in the brainstem, cerebellum, multisensory cortex, and basal ganglia during the entire observation period post-BL. nGVS broadly reversed brain activity adaptions occurring in the natural course post-BL. The parallel behavioral locomotor assessment demonstrated a beneficial treatment effect of nGVS on sensory-ataxic gait alterations, particularly in the early stage of post-BL recovery. Stimulation-induced locomotor improvements were finally linked to nGVS brain activity responses in the brainstem, hemispheric motor, and limbic networks. In conclusion, combined 18F-FDG-PET and locomotor analysis discloses the potential neurophysiological and neuroanatomical substrates that mediate previously observed therapeutic nGVS effects on postural deficits in patients with BVL.

Noisy galvanic vestibular stimulation influences head stability in young healthy adults while standing on a moving platform

BackgroundThe ability to stand with eyes closed on a sinusoidal translational moving platform may be affected by spatial orientation owing to vestibular input information. Moreover, changes in the frequency of the moving platform may affect the sensory reweighting through somatosensory and vestibular sensations. However, it is unclear whether noisy galvanic vestibular stimulation (nGVS), which activates vestibular-related brain regions, affects the stability of individuals standing on a platform moving at different frequencies. Research questionDo vestibular stimulation by nGVS and changes in the frequency of translationally moving platforms affect the standing stability of individuals? MethodsThirty-one healthy young adult participants were provided both sham and nGVS interventions while they maintained a static standing position, with their eyes closed, on an anterior-posterior sinusoidal translation platform. The nGVS was adapted to an optimal intensity below the perceptual threshold (frequency band: 100–640 Hz), and the sham stimulus was adapted to 0 µA. The participants were randomly assessed for postural stability at 0.2, 0.6, and 1.2 Hz moving platform frequencies for 80 s each under both stimulus conditions. Postural stability was calculated as the root mean square (RMS) sway from head accelerations in the anteroposterior (AP) and mediolateral (ML) directions for 50 s between 20 and 70 s during the 80 s period, measured using an inertial sensor placed on the external occipital ridge. ResultsnGVS significantly reduced the RMS sway of head acceleration in the AP direction compared with sham stimulation. Furthermore, nGVS significantly reduced RMS sway in the ML direction compared with sham stimulation at a 1.2 Hz moving platform oscillation. SignificanceThese findings suggest that postural adjustment by the vestibular system influences head stability on a moving platform at specific sinusoidal translation frequencies, suggesting that nGVS may reduce head sway.

Additive Sensory Noise Effects on Operator Performance in a Lunar Landing Simulation.

INTRODUCTION: Adding noise to a system to improve a weak signal's detectability is known as stochastic resonance (SR). SR has been shown to improve sensory perception and cognitive performance in certain individuals, but it is unknown whether this performance improvement can translate to meaningful macrocognitive enhancements in performance for complex, operational tasks.OBJECTIVE: We investigated human operator performance in a lunar landing simulation while applying auditory white noise and/or noisy galvanic vestibular stimulation.METHODS: We measured performance (N = 16 subjects) while completing simulation trials in our Aerospace Research Simulator. Trials were completed with and without the influence of auditory white noise, noisy galvanic vestibular stimulation, and both simultaneously in a multimodal fashion. Performance was observed holistically and across subdimensions of the task, which included flight skill and perception. Subjective mental workload was collected after completing four trials in each treatment.RESULTS: We did not find broad operator improvement under the influence of noise, but a significant interaction was identified between subject and noise treatment, indicating that some subjects were impacted by additive noise. We also found significant interactions between subject and noise treatment in performance subdimensions of flight skill and perception. We found no significant main effects on mental workload.CONCLUSIONS: This study investigated the utility of using additive sensory noise to induce SR for complex tasks. While SR has been shown to improve aspects of performance, our results suggest additive noise does not yield operational performance changes for a broad population, but specific individuals may be affected.Sherman SO, Shen Y-Y, Gutierrez-Mendoza D, Schlittenhart M, Watson C, Clark TK, Anderson AP. Additive sensory noise effects on operator performance in a lunar landing simulation. Aerosp Med Hum Perform. 2023; 94(10):770-779.

Finding Balance with Vestibular Stimulation

Weakening of the vestibular system through disease or aging leads to imbalance, restricted mobility, and falls (Hain et al., 2018). Vestibular weakness affects one-third of people over the age of 40, and 85% of those over 80 years (Agrawal et al., 2009). The delicate cells of the vestibular system do not regenerate and thus it becomes an incurable chronic condition. A promising treatment is noisy galvanic vestibular stimulation (nGVS), a non-invasive electrical stimulation, delivered to the vestibular system, aiming to restore absent vestibular information and improve balance (McLaren et al., 2022). This presentation reports the results of a scoping review investigating the stimulation parameters that can be manipulated to improve the efficacy of nGVS. A comprehensive systematic search of five databases up to December 2022 identified studies applying nGVS to people with the aim of improving their postural control. Two independent reviewers screened and identified eligible studies and extracted parameter data. Thirty-one studies met the eligibility criteria. The review identified that a broad array of settings have been employed across studies. The nGVS parameters of waveform, amplitude, frequency band, duration of stimulation, method of amplitude optimization, size and composition of electrodes and the electrode skin interface are all likely to influence the efficacy of nGVS. However, the ability to draw robust conclusions about the selection of optimal nGVS parameters is hindered by a lack of studies that directly compare parameter settings. I propose a guideline for the accurate reporting of nGVS parameters. This will help establish standardized stimulation protocols bringing us one step closer to becoming a readily available clinical treatment.

Optimal Design of Galvanic Vestibular Stimulation for Patients with Vestibulopathy and Cerebellar Disorders.

Galvanic vestibular stimulation (GVS) has shown positive outcomes in various neurological and psychiatric disorders, such as enhancing postural balance and cognitive functions. In order to expedite the practical application of GVS in clinical settings, our objective was to determine the best GVS parameters for patients with vestibulopathy and cerebellar disorders using optimal design calculation. A total of 31 patients (26 males, mean age 57.03 ± 14.75 years, age range 22-82 years) with either unilateral or bilateral vestibulopathy (n = 18) or cerebellar ataxia (n = 13) were enrolled in the study. The GVS intervention included three parameters, waveform (sinusoidal, direct current [DC], and noisy), amplitude (0.4, 0.8, and 1.2 mA), and duration of stimulation (5 and 30 min), resulting in a total of 18 GVS intervention modes as input variables. To evaluate the effectiveness of GVS, clinical vertigo and gait assessments were conducted using the Dizziness Visual Analogue Scale (D-VAS), Activities-specific Balance Confidence Scale (ABC), and Scale for Assessment and Rating of Ataxia (SARA) as output variables. Optimal design and local sensitivity analysis were employed to determine the most optimal GVS modes. Patients with unilateral vestibulopathy experienced the most favorable results with either noisy or sinusoidal GVS at 0.4 mA amplitude for 30 min, followed by DC GVS at 0.8 mA amplitude for 5 min. Noisy GVS at 0.8 or 0.4 mA amplitude for 30 min demonstrated the most beneficial effects in patients with bilateral vestibulopathy. For patients with cerebellar ataxia, the optimal choices were noisy GVS with 0.8 or 0.4 mA amplitude for 5 or 30 min. This study is the first to utilize design optimization methods to identify the GVS stimulation parameters that are tailored to individual-specific characteristics of dizziness and imbalance. A sensitivity analysis was carried out along with the optimal design to offset the constraints of a limited sample size, resulting in the identification of the most efficient GVS modes for patients suffering from vestibular and cerebellar disorders.

Combining Vestibular Rehabilitation and Noisy Galvanic Vestibular Stimulation for Treatment of Unilateral Vestibulopathy: A Randomized Controlled Trial

Background and Aim: Vestibular Rehabilitation (VR) is a well-accepted treatment for Unilateral Vestibulopathy (UVP). Since noisy Galvanic Vestibular Stimulation (nGVS) improves the processing of vestibular inputs, we assessed the synergistic effects of adding nGVS to vestibular rehabilitation for the treatment of UVP.
 Methods: Patients with UVP were randomly assigned into two groups receiving either VR for four weeks (VR group, n=12) or VR for four weeks combined with nGVS for three sessions (VR+nGVS group; n=12). Outcome measurements were postural control parameters measured with eyes open/closed conditions on hard/soft surfaces, Vestibulo-Ocular Reflex (VOR) gain, and Dizziness Handicap Inventory (DHI) scores that were assessed at baseline and after four weeks.
 Results: All postural control parameters, mean total and subscale scores of DHI, and mean VOR gain in directions of affected canals significantly improved in both groups after interventions (p<0.05) except mean mediolateral displacement in conditions with eyes closed on hard surface and with eyes open on soft surface, mean mediolateral velocity in conditions with eyes closed on hard surface, ability to stance with eye closed condition on soft surface and mean emotional subscale of DHI in VR group. Improvements were significantly higher in postural control outcomes measured in stances with eyes closed on hard surface and with eyes open and closed on soft surface, mean VOR gains in directions of affected horizontal and anterior canals, and mean total, physical, and functional scores of DHI in VR+nGVS group (p<0.05).
 Conclusion: When combined with VR, nGVS shows additional therapeutic effects in UVP patients.
 Keywords: Unilateral peripheral vestibulopathy; vestibular compensation; galvanic vestibular stimulation; vestibular rehabilitation; postural control

Training augmentation using additive sensory noise in a lunar rover navigation task.

The uncertain environments of future space missions means that astronauts will need to acquire new skills rapidly; thus, a non-invasive method to enhance learning of complex tasks is desirable. Stochastic resonance (SR) is a phenomenon where adding noise improves the throughput of a weak signal. SR has been shown to improve perception and cognitive performance in certain individuals. However, the learning of operational tasks and behavioral health effects of repeated noise exposure aimed to elicit SR are unknown. We evaluated the long-term impacts and acceptability of repeated auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS) on operational learning and behavioral health. Subjects (n = 24) participated in a time longitudinal experiment to access learning and behavioral health. Subjects were assigned to one of our four treatments: sham, AWN (55 dB SPL), nGVS (0.5 mA), and their combination to create a multi-modal SR (MMSR) condition. To assess the effects of additive noise on learning, these treatments were administered continuously during a lunar rover simulation in virtual reality. To assess behavioral health, subjects completed daily, subjective questionnaires related to their mood, sleep, stress, and their perceived acceptance of noise stimulation. We found that subjects learned the lunar rover task over time, as shown by significantly lower power required for the rover to complete traverses (p < 0.005) and increased object identification accuracy in the environment (p = 0.05), but this was not influenced by additive SR noise (p = 0.58). We found no influence of noise on mood or stress following stimulation (p > 0.09). We found marginally significant longitudinal effects of noise on behavioral health (p = 0.06) as measured by strain and sleep. We found slight differences in stimulation acceptability between treatment groups, and notably nGVS was found to be more distracting than sham (p = 0.006). Our results suggest that repeatedly administering sensory noise does not improve long-term operational learning performance or affect behavioral health. We also find that repetitive noise administration is acceptable in this context. While additive noise does not improve performance in this paradigm, if it were used for other contexts, it appears acceptable without negative longitudinal effects.

Combination of Vestibular Rehabilitation and Galvanic VestibularStimulation ImprovesVerbal andVisuospatial Memory: A Randomized Control Trial in Patients with Amnestic Mild Cognitive Impairment

Background and Aim: Considering the critical input of the vestibular system to the hippocampus as an area involved in cognition, and vestibular disorders reported in patients with amnestic Mild Cognitive Impairment (aMCI), we aimed to investigate the effects of Vestibular Rehabilitation (VR) with and without noisy Galvanic Vestibular Stimulation (nGVS) on cognitive function in patients with aMCI.&#x0D; Methods: In a randomized controlled trial, twenty-two patients with aMCI were randomly assigned to two groups receiving: 1) VR for four weeks (VR group); 2) VR for four weeks with nGVS for three sessions (GVS+VR group). Outcome measures were Rey's Auditory-Verbal Learning Test (RAVLT), Corsi blocks, Visual Search (VS), and match to sample tests.&#x0D; Results: Mean immediate and delayed recalls of RAVLT, all of the outcomes of Corsi blocks and VS tests, and the error rate of the match to sample tests improved significantly after intervention in VR and GVS+VR groups. Between-group differences were observed for learning and delayed recalls of RAVLT (p=0.001, d=0.444 and p&lt;0.001, d=0.512 respectively), reaction times 1 and 2 in VS (p=0.007, d=0.325 and p=0.001, d=0.446 respectively), the total correct trial of Corsi blocks (p=0.026, d=0.235), and error rate of the match to sample (p=0.017, d=0.266) tests.&#x0D; Conclusion: The synergistic effect of VR and GVS suggested that simultaneous use of both stimulations improves verbal and visuospatial memory in aMCI patients. Study protocol location: https://irct.ir/trial/47249 Trial registration number: IRCT20160131026279N3&#x0D; Keywords: Mild cognitive impairment; spatial memory; verbal memory; hippocampus; galvanic vestibular stimulation; vestibular rehabilitation

Effects of noisy galvanic vestibular stimulation on functional reach test

Balance disorders are a risk factor for falls in older individuals, and an increased center of pressure (COP) sway path length during standing and decreased reach distance in the functional reach test (FRT) predispose them to falls. Reportedly, noisy galvanic vestibular stimulation (nGVS) reduces COP sway path length during standing in young and community-dwelling older individuals and suggested to be a promising approach to improve balance function. However, the effect of nGVS on FRT remains unclear. Therefore, this study aimed to clarify the effect of nGVS on the FRT reach distance. This study has a cross-over design and included 20 healthy young adults. Interventions under nGVS (stimulation intensity: 0.2 mA) and sham (stimulation intensity: 0 mA) conditions were randomly administered to each participant. The participants underwent COP sway during standing measurements and FRT pre-intervention and post-intervention under each condition, and COP sway path length and the FRT reach distance were calculated. Statistical analysis revealed a significant decrease in post-intervention COP sway path length compared with pre-intervention COP sway path length under the nGVS condition. Conversely, the FRT reach distance remained the same under both nGVS and sham conditions. Thus, nGVS may improve the standing balance function but cannot change the FRT reach distance in healthy young individuals.

Effects of additive sensory noise on cognition.

Adding noise to a system to improve a weak signal's throughput is known as stochastic resonance (SR). SR has been shown to improve sensory perception. Some limited research shows noise can also improve higher order processing, such as working memory, but it is unknown whether SR can broadly improve cognition. We investigated cognitive performance while applying auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS). We measured cognitive performance (n = 13 subjects) while completing seven tasks in the cognition test battery (CTB). Cognition was assessed with and without the influence of AWN, nGVS, and both simultaneously. Performance in speed, accuracy, and efficiency was observed. A subjective questionnaire regarding preference for working in noisy environments was collected. We did not find broad cognitive performance improvement under the influence of noise (p > 0.1). However, a significant interaction was found between subject and noise condition for accuracy (p = 0.023), indicating that some subjects exhibited cognitive changes with the addition of noise. Across all metrics, noisy environment preference may trend to be a potential indicator of whether subjects will exhibit SR cognitive benefits with a significant predictor in efficiency (p = 0.048). This study investigated using additive sensory noise to induce SR in overall cognition. Our results suggest that using noise to improve cognition is not applicable for a broad population; however, the effect of noise differs across individuals. Further, subjective questionnaires may be a means to identify which individuals are sensitive to SR cognitive benefits, but further investigation is needed.

Enhancement of Vestibular Motion Discrimination by Small Stochastic Whole-body Perturbations in Young Healthy Humans

Noisy galvanic vestibular stimulation has been shown to improve vestibular perception in healthy subjects. Here, we sought to obtain similar results using more natural stimuli consisting of small-amplitude motion perturbations of the whole body. Thirty participants were asked to report the perceived direction of antero-posterior sinusoidal motion on a MOOG platform. We compared the baseline perceptual thresholds with those obtained by applying small, stochastic perturbations at different power levels along the antero-posterior axis, symmetrically distributed around a zero-mean. At the population level, we found that the thresholds for all but the highest level of noise were significantly lower than the baseline threshold. At the individual level, the threshold was lower with at least one noise level than the threshold without noise in 87% of participants. Thus, small, stochastic oscillations of the whole body can increase the probability of recognizing the direction of motion from low, normally subthreshold vestibular signals, possibly due to stochastic resonance mechanisms. We suggest that, just as the external noise of the present experiments, also the spontaneous random oscillations of the head and body associated with standing posture are beneficial by enhancing vestibular thresholds with a mechanism similar to stochastic resonance.

Efficacy of nGVS to improve postural stability in people with Bilateral Vestibulopathy

Bilateral vestibulopathy occurs when the neural signals from the balance organs (vestibular apparatus) to the brain are weak. This leads to imbalance and blurry vision during head movements (Fujimoto et al., 2019). To date, there are few successful treatment options once damage has occurred (Hain et al., 2018). Noisy galvanic vestibular stimulation (nGVS) is a non-invasive electrical stimulation, delivered at a low level to the vestibular system. When used to boost the weak physiological signal from the vestibular system nGVS has the potential to restore absent vestibular information and improve balance (Dlugaiczyk et al., 2019). This presentation will include the results of my systematic literature review and meta-analysis, examining the evidence for the use of nGVS as a means of improving postural control in people with bilateral vestibulopathy and discussing how these results will inform my research. A comprehensive systematic search of five databases up to July 2022 was performed. The search identified studies applying nGVS to people with bilateral vestibulopathy, with the aim of improving their postural control. Two independent reviewers screened and identified eligible studies, completed a Cochrane risk of bias evaluation, and extracted relevant data. Seven studies met the eligibility criteria with 5 studies being suitable for meta-analysis. The standardized mean difference (SMD) based on Hedges’ g was calculated as a measure of effect size, for the primary outcome measure that best identified postural control, and a forest plot generated. Meta-analysis found that nGVS improved postural control during standing and walking (pooled SMD = 0.47 95% CI, [0.25, 0.7]). nGVS-mediated improvements in postural control were most evident standing on a firm surface with eyes closed, and in measures of lateral stability during gait. Identifying that nGVS is effective in people with bilateral vestibulopathy, and that the efficacy is context-specific, will help inform the development of treatments for people with bilateral vestibulopathy.

Noisy galvanic vestibular stimulation improves vestibular perception in bilateral vestibulopathy

BackgroundPatients with bilateral vestibulopathy (BVP) suffer from impaired vestibular motion perception that is linked to deficits in spatial memory and navigation.ObjectiveTo examine the potential therapeutic effect of imperceptible noisy galvanic vestibular stimulation (nGVS) on impaired vestibular perceptual performance in BVP.MethodsIn 11 patients with BVP (mean age: 54.0 ± 8.3 years, 7 females), we initially determined the nGVS intensity that optimally stabilizes balance during a static posturographic assessment. Subsequently, effects of optimal nGVS vs. sham stimulation on vestibular motion perception were examined in randomized order. Vestibular perceptual performance was determined as direction recognition thresholds for head-centered roll tilt motion on a 6DOF motion platform in the absence of any visual or auditory motion cues.ResultsFor each patient, an nGVS intensity that optimally stabilized static balance compared to sham stimulation could be identified (mean 0.36 ± 0.16 mA). nGVS at optimal intensity resulted in lowered vestibular perceptual thresholds (0.94 ± 0.30 deg/s) compared to sham stimulation (1.67 ± 1.11 deg/s; p = 0.040). nGVS-induced improvements in vestibular perception were observed in 8 of 11 patients (73%) and were greater in patients with poorer perceptual performance during sham stimulation (R = − 0.791; p = 0.007).ConclusionsnGVS is effective in improving impaired vestibular motion perception in patients with BVP, in particular in those patients with poor baseline perceptual performance. Imperceptible vestibular noise stimulation might thus offer a non-invasive approach to target BVP-related impairments in spatial memory, orientation, and navigation.

Effects of Low-Intensity Vestibular Noise Stimulation on Postural Instability in Patients with Parkinson's Disease.

Postural instability is a major disabling factor in patients with advanced Parkinson's disease (PD) and often resistant to treatment. Previous studies indicated that imbalance in PD may be reduced by low-intensity noisy galvanic vestibular stimulation (nGVS). To investigate the potential mode of action of this therapeutic effect. In particular, we examined whether nGVS-induced reductions of body sway in PD are compatible with stochastic resonance (SR), a mechanism by which weak sensory noise stimulation can paradoxically enhance sensory information transfer. Effects of nGVS of varying intensities (0-0.7 mA) on body sway were examined in 15 patients with PD standing with eye closed on a posturographic force plate. We assumed a bell-shaped response curve with maximal reductions of sway at intermediate nGVS intensities to be indicative of SR. An established SR-curve model was fitted on individual patient outcomes and three experienced human raters had to judge whether responses to nGVS were consistent with the exhibition of SR. nGVS-induced reductions of body sway compatible with SR were found in 10 patients (67%) with optimal improvements of 23±13%. In 7 patients (47%), nGVS-induced sway reductions exceeded the minimally important clinical difference (optimal improvement: 30±10%), indicative of strong SR. This beneficial effect was more likely in patients with advanced PD (R = 0.45; p = 0.045). At least half of the assessed patients showed robust improvements in postural balance compatible with SR when treated with low-intensity nGVS. In particular, patients with more advanced disease stages and imbalance may benefit from the non-invasive and well-tolerated treatment with nGVS.

Effects of Noisy Galvanic Vestibular Stimulation on the Muscle Activity and Joint Movements in Different Standing Postures Conditions.

ObjectiveNoisy galvanic vestibular stimulation (nGVS) is an effective method for stabilizing posture; however, little is known regarding the detailed muscle activity and joint movement in the standing posture. This study aimed to clarify the changes in the lower limb muscle activity and joint angular velocity by nGVS intervention using the simultaneous assessment method of inertial measurement units and surface electromyography (EMG).MethodsSeventeen healthy participants were assessed for their physical responses under four conditions (standing on a firm surface with eyes-open/eyes-closed, and a foam surface with eyes-open/eyes-closed) without stimulation (baseline) and with stimulation (sham or nGVS). Noise stimuli were applied for 30 s at a level below the perceptual threshold. The body control response was evaluated using EMG activity and angular velocity of the lower limbs.ResultRegarding the change from baseline for each parameter, there was a significant interactive effect of EMG activity in the muscle type × intervention and EMG activity and angular velocity in the condition × intervention. Post hoc analysis revealed that the angular velocity was significantly decreased in the abduction-adduction direction in the standing on a foam surface with eyes-closed condition compared to that with eyes-open in the nGVS intervention.ConclusionOur results suggest that nGVS altered physical responses in different standing postural conditions. The present study is exploratory and therefore the evidence should be investigated in future studies specifically target those muscle activities and joint motion parameters.