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Mohammed A, Li S, Liu X. Exploring the Potentials of Wearable Technologies in Managing Vestibular Hypofunction. Bioengineering (Basel) 2024; 11:641. [PMID: 39061723 PMCID: PMC11274252 DOI: 10.3390/bioengineering11070641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2024] [Revised: 05/26/2024] [Accepted: 05/31/2024] [Indexed: 07/28/2024] Open
Abstract
The vestibular system is dedicated to gaze stabilization, postural balance, and spatial orientation; this makes vestibular function crucial for our ability to interact effectively with our environment. Vestibular hypofunction (VH) progresses over time, and it presents differently in its early and advanced stages. In the initial stages of VH, the effects of VH are mitigated using vestibular rehabilitation therapy (VRT), which can be facilitated with the aid of technology. At more advanced stages of VH, novel techniques that use wearable technologies for sensory augmentation and sensory substitution have been applied to manage VH. Despite this, the potential of assistive technologies for VH management remains underexplored over the past decades. Hence, in this review article, we present the state-of-the-art technologies for facilitating early-stage VRT and for managing advanced-stage VH. Also, challenges and strategies on how these technologies can be improved to enable long-term ambulatory and home use are presented.
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Affiliation(s)
- Ameer Mohammed
- School of Information Science and Technology, Fudan University, Shanghai 200433, China; (A.M.); (S.L.)
- State Key Laboratory of Integrated Chips and Systems, Fudan University, Shanghai 201203, China
| | - Shutong Li
- School of Information Science and Technology, Fudan University, Shanghai 200433, China; (A.M.); (S.L.)
- State Key Laboratory of Integrated Chips and Systems, Fudan University, Shanghai 201203, China
| | - Xiao Liu
- School of Information Science and Technology, Fudan University, Shanghai 200433, China; (A.M.); (S.L.)
- State Key Laboratory of Integrated Chips and Systems, Fudan University, Shanghai 201203, China
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Abstract
PURPOSE OF REVIEW Electrical stimulation of the peripheral and central vestibular system using noninvasive (galvanic vestibular stimulation, GVS) or invasive (intracranial electrical brain stimulation, iEBS) approaches have a long history of use in studying self-motion perception and balance control. The aim of this review is to summarize recent electrophysiological studies of the effects of GVS, and functional mapping of the central vestibular system using iEBS in awake patients. RECENT FINDINGS The use of GVS has become increasingly common in the assessment and treatment of a wide range of clinical disorders including vestibulopathy and Parkinson's disease. The results of recent single unit recording studies have provided new insight into the neural mechanisms underlying GVS-evoked improvements in perceptual and motor responses. Furthermore, the application of iEBS in patients with epilepsy or during awake brain surgery has provided causal evidence of vestibular information processing in mostly the middle cingulate cortex, posterior insula, inferior parietal lobule, amygdala, precuneus, and superior temporal gyrus. SUMMARY Recent studies have established that GVS evokes robust and parallel activation of both canal and otolith afferents that is significantly different from that evoked by natural head motion stimulation. Furthermore, there is evidence that GVS can induce beneficial neural plasticity in the central pathways of patients with vestibular loss. In addition, iEBS studies highlighted an underestimated contribution of areas in the medial part of the cerebral hemispheres to the cortical vestibular network.
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Affiliation(s)
- Christophe Lopez
- Aix Marseille Univ, CNRS, Laboratory of Cognitive Neuroscience (LNC), FR3C, Marseille, France
| | - Kathleen E. Cullen
- Department of Biomedical Engineering, Johns Hopkins University
- Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University
- Department of Neuroscience, Johns Hopkins University
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore 21205 MD, USA
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Sherman SO, Jonsen A, Lewis Q, Schlittenhart M, Szafir D, Clark TK, Anderson AP. Training augmentation using additive sensory noise in a lunar rover navigation task. Front Neurosci 2023; 17:1180314. [PMID: 37424995 PMCID: PMC10326282 DOI: 10.3389/fnins.2023.1180314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 05/31/2023] [Indexed: 07/11/2023] Open
Abstract
Background 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. Objective 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. Methods 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. Results 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). Conclusion 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.
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Affiliation(s)
- Sage O. Sherman
- Ann & H.J. Smead Department of Aerospace Engineering Sciences, The University of Colorado Boulder, Boulder, CO, United States
| | - Anna Jonsen
- Ann & H.J. Smead Department of Aerospace Engineering Sciences, The University of Colorado Boulder, Boulder, CO, United States
| | - Quinlan Lewis
- Ann & H.J. Smead Department of Aerospace Engineering Sciences, The University of Colorado Boulder, Boulder, CO, United States
| | - Michael Schlittenhart
- Ann & H.J. Smead Department of Aerospace Engineering Sciences, The University of Colorado Boulder, Boulder, CO, United States
| | - Daniel Szafir
- Department of Computer Science, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Torin K. Clark
- Ann & H.J. Smead Department of Aerospace Engineering Sciences, The University of Colorado Boulder, Boulder, CO, United States
| | - Allison P. Anderson
- Ann & H.J. Smead Department of Aerospace Engineering Sciences, The University of Colorado Boulder, Boulder, CO, United States
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Kim S, Lazaro MJ, Kang Y. Galvanic vestibular stimulation to counteract leans illusion: comparing step and ramped waveforms. ERGONOMICS 2023; 66:432-442. [PMID: 35730683 DOI: 10.1080/00140139.2022.2093403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
Leans is a common type of Spatial Disorientation (SD) illusion that causes pilots to be confused about the position of the aircraft during a flight. This illusion could lead to serious adverse effects and even flight mishaps. Therefore, an effective means to deal with leans is crucial for flight safety. This study aims to investigate the effects of Galvanic Vestibular Stimulation (GVS) technology with different waveforms as a tool to mitigate the negative effects of leans. 20 Air Force pilots participated in leans-induced flight simulation experiment with three GVS conditions (without-GVS, step-GVS, ramped-GVS). Bank angle error, subjective SD, perceived strength, and annoyance were measured as the dependent variables. Analysis revealed that step-GVS and ramped-GVS yielded lower bank angle errors and subjective SD than without-GVS. In addition, annoyance ratings were lower for ramped-GVS than step-GVS. This study suggests that GVS has the potential to be utilised as a counteracting tool to cope with leans.Practitioner summary: Galvanic Vestibular Stimulation (GVS) can be utilised as a tool to counteract the detrimental effects of leans illusion, specifically the ramped style GVS, considering that it is less annoying and distracting for the pilots. In general, GVS induces a roll sensation that can offset the false sensation caused by the leans, which can potentially help maintain flight safety and avoid spatial disorientation-related accidents.Abbreviations: SD: spatial disorientation; GVS: galvanic vestibular stimulation; MSSQ: motion sickness susceptibility questionniare; SSQ: simulator sickness questionnaire; BLE: bluetooth low energy; PCB: printed circuit board; RPM: revolution per minute.
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Affiliation(s)
- Sungho Kim
- Department of Systems Engineering, Republic of Korea Air Force Academy, Cheongju, South Korea
| | - May Jorella Lazaro
- Interdisciplinary Program in Cognitive Science, Seoul National University, Seoul, South Korea
| | - Yohan Kang
- Department of Industrial Engineering, Seoul National University, Seoul, South Korea
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Abbariki F, Mikhail Y, Hamadjida A, Charron J, Mac-Thiong JM, Barthélemy D. Effect of galvanic vestibular stimulation applied at the onset of stance on muscular activity and gait cycle duration in healthy individuals. Front Neural Circuits 2023; 16:1065647. [PMID: 36845254 PMCID: PMC9946991 DOI: 10.3389/fncir.2022.1065647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 12/28/2022] [Indexed: 02/11/2023] Open
Abstract
Locomotion requires the complex involvement of the spinal and supraspinal systems. So far, the role of vestibular input in gait has been assessed mainly with respect to gait stability. The noninvasive technique of galvanic vestibular stimulation (GVS) has been reported to decrease gait variability and increase gait speed, but the extent of its effect on spatiotemporal gait parameters is not fully known. Objective: Characterize vestibular responses during gait and determine the influence of GVS on cycle duration in healthy young participants. Methods: Fifteen right-handed individuals participated in the study. Electromyography (EMG) recordings of the bilateral soleus (SOL) and tibialis anterior muscles (TA) were performed. First, to determine stimulation intensity, an accelerometer placed on the vertex recorded the amplitude of the head tilts evoked by the GVS (1-4 mA, 200 ms) to establish a motor threshold (T). Second, while participants walked on a treadmill, GVS was applied at the onset of the stance phase during the treadmill gait with an intensity of 1 and 1.5 T with the cathode behind the right (RCathode) or left ear (LCathode). EMG traces were rectified, averaged (n = 30 stimuli), and analyzed. Latency, duration, and amplitude of vestibular responses as well as the mean duration of the gait cycles were measured. Results: GVS mainly induced long-latency responses in the right SOL, right TA and left TA. Only short-latency responses were triggered in the left SOL. Responses in the right SOL, left SOL and left TA were polarity dependent, being facilitatory with RCathode and inhibitory with LCathode, whereas responses in the right TA remained facilitatory regardless of the polarity. With the RCathode configuration, the stimulated cycle was prolonged compared with the control cycle at both 1 and 1.5 T, due to prolonged left SOL and TA EMG bursts, but no change was observed in right SOL and TA. With LCathode, GVS did not modify the cycle duration. Conclusion: During gait, a brief, low-intensity GVS pulse delivered at the right stance onset induced mainly long-latency polarity-dependent responses. Furthermore, a RCathode configuration increased the duration of the stimulated gait cycle by prolonging EMG activity on the anodic side. A similar approach could be explored to influence gait symmetry in individuals with neurological impairment.
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Affiliation(s)
- Faezeh Abbariki
- School of Rehabilitation, Université de Montréal, Montreal, QC, Canada
- Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR) and Centre Intégré Universitaire en Santé et Services Sociaux (CIUSSS) du Centre-Sud-de-l’Île-de-Montréal, Montreal, QC, Canada
| | - Youstina Mikhail
- Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - Adjia Hamadjida
- Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Live Science, Higher Teacher Training College of Bertoua, University of Bertoua, Bertoua, Cameroon
| | - Jonathan Charron
- Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - Jean-Marc Mac-Thiong
- Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Centre Intégré Universitaire en Santé et Services Sociaux du nord de l’île de Montréal (CIUSSS NIM), Hôpital du Sacré-coeur de Montréal (HSCM), Montréal, QC, Canada
| | - Dorothy Barthélemy
- School of Rehabilitation, Université de Montréal, Montreal, QC, Canada
- Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR) and Centre Intégré Universitaire en Santé et Services Sociaux (CIUSSS) du Centre-Sud-de-l’Île-de-Montréal, Montreal, QC, Canada
- Centre Intégré Universitaire en Santé et Services Sociaux du nord de l’île de Montréal (CIUSSS NIM), Hôpital du Sacré-coeur de Montréal (HSCM), Montréal, QC, Canada
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Noisy galvanic vestibular stimulation improves vestibular perception in bilateral vestibulopathy. J Neurol 2023; 270:938-943. [PMID: 36324034 PMCID: PMC9886588 DOI: 10.1007/s00415-022-11438-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 11/06/2022]
Abstract
BACKGROUND Patients with bilateral vestibulopathy (BVP) suffer from impaired vestibular motion perception that is linked to deficits in spatial memory and navigation. OBJECTIVE To examine the potential therapeutic effect of imperceptible noisy galvanic vestibular stimulation (nGVS) on impaired vestibular perceptual performance in BVP. METHODS In 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. RESULTS For 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). CONCLUSIONS nGVS 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.
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McLaren R, Smith PF, Taylor RL, Niazi IK, Taylor D. Scoping out noisy galvanic vestibular stimulation: a review of the parameters used to improve postural control. Front Neurosci 2023; 17:1156796. [PMID: 37205050 PMCID: PMC10187481 DOI: 10.3389/fnins.2023.1156796] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 04/04/2023] [Indexed: 05/21/2023] Open
Abstract
Objective Noisy galvanic vestibular stimulation (nGVS) has been used to facilitate vestibular function and improve gait and balance in people with poor postural control. The aim of this scoping review is to collate, summarize and report on the nGVS parameters that have been used to augment postural control. Method A systematic scoping review was conducted up to December 2022. Data were extracted and synthesized from 31 eligible studies. Key nGVS parameters were identified, and the importance of these parameters and their influence on postural control evaluated. Results A range of nGVS parameters have been used to augment postural control, including; noise waveform, amplitude, frequency band, duration of stimulation, method of amplitude optimization, size and composition of electrodes and the electrode skin interface. Conclusion Systematic evaluation of the individual parameters that can be manipulated in the nGVS waveform identified that a broad array of settings have been utilized in each parameter across the studies. Choices made around the electrode and electrode-skin interface, as well as the amplitude, frequency band, duration and timing of the waveform are likely to influence the efficacy of nGVS. The ability to draw robust conclusions about the selection of optimal nGVS parameters to improve postural control, is hindered by a lack of studies that directly compare parameter settings or consider the variability in individuals' response to nGVS. We propose a guideline for the accurate reporting of nGVS parameters, as a first step toward establishing standardized stimulation protocols.
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Affiliation(s)
- Ruth McLaren
- Rehabilitation Innovation Centre, Health and Rehabilitation Research Institute, School of Clinical Sciences, Auckland University of Technology, Auckland, New Zealand
- Eisdell Moore Centre for Hearing and Balance Research, University of Auckland, Auckland, New Zealand
- *Correspondence: Ruth McLaren,
| | - Paul F. Smith
- Eisdell Moore Centre for Hearing and Balance Research, University of Auckland, Auckland, New Zealand
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, The Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - Rachael L. Taylor
- Eisdell Moore Centre for Hearing and Balance Research, University of Auckland, Auckland, New Zealand
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Imran Khan Niazi
- Rehabilitation Innovation Centre, Health and Rehabilitation Research Institute, School of Clinical Sciences, Auckland University of Technology, Auckland, New Zealand
- Centre of Chiropractic Research, New Zealand College of Chiropractic, Auckland, New Zealand
- Centre for Sensory-Motor Interactions, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Denise Taylor
- Rehabilitation Innovation Centre, Health and Rehabilitation Research Institute, School of Clinical Sciences, Auckland University of Technology, Auckland, New Zealand
- Eisdell Moore Centre for Hearing and Balance Research, University of Auckland, Auckland, New Zealand
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McLaren R, Smith PF, Taylor RL, Ravindran S, Rashid U, Taylor D. Efficacy of nGVS to improve postural stability in people with bilateral vestibulopathy: A systematic review and meta-analysis. Front Neurosci 2022; 16:1010239. [PMID: 36248647 PMCID: PMC9553993 DOI: 10.3389/fnins.2022.1010239] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 08/24/2022] [Indexed: 11/25/2022] Open
Abstract
Objective Noisy galvanic vestibular stimulation (nGVS) has been used to boost vestibular afferent information to the central nervous system. This has the potential to improve postural control for people for whom vestibular signals are weak, such as in bilateral vestibulopathy (BVP). The aim of this systematic review and meta-analysis is to investigate the evidence for nGVS as a modality to improve postural control in people with BVP. Methods A comprehensive systematic search was conducted of five databases up to July 2022 to find studies applying nGVS to people with BVP, with the aim of improving postural control. Two independent reviewers screened and identified eligible studies, completed a risk of bias evaluation (Cochrane) and extracted relevant data. 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. Results Seven studies met the eligibility criteria, with five being suitable for meta-analysis. Meta-analysis revealed a moderate effect in favor of nGVS improving 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 in observations of reduced sway velocity when standing on a firm surface with eyes closed, and in the reduced variability of gait parameters, particularly those measuring lateral stability. Conclusions Coincident nGVS in people with BVP improves postural control during standing and walking. This improvement appears to be context specific, in that vestibular augmentation is most effective in situations where visual inputs are limited, and where reliable context specific proprioceptive cues are available. Further research is warranted investigating additional circumstances in which nGVS improves postural control, including investigating the residual, and sustained effects of nGVS. Systematic review registration https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=342147, identifier: 342147.
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Affiliation(s)
- Ruth McLaren
- Rehabilitation Innovation Centre, Health and Rehabilitation Research Institute, School of Clinical Science, Auckland University of Technology, Auckland, New Zealand
- *Correspondence: Ruth McLaren
| | - Paul F. Smith
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, The Brain Health Research Centre, University of Otago, Dunedin, New Zealand
- Eisdell Moore Centre for Hearing and Balance Research, University of Auckland, Auckland, New Zealand
| | - Rachael L. Taylor
- Eisdell Moore Centre for Hearing and Balance Research, University of Auckland, Auckland, New Zealand
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Shobika Ravindran
- Rehabilitation Innovation Centre, Health and Rehabilitation Research Institute, School of Clinical Science, Auckland University of Technology, Auckland, New Zealand
| | - Usman Rashid
- Rehabilitation Innovation Centre, Health and Rehabilitation Research Institute, School of Clinical Science, Auckland University of Technology, Auckland, New Zealand
| | - Denise Taylor
- Rehabilitation Innovation Centre, Health and Rehabilitation Research Institute, School of Clinical Science, Auckland University of Technology, Auckland, New Zealand
- Eisdell Moore Centre for Hearing and Balance Research, University of Auckland, Auckland, New Zealand
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Matsugi A, Shiozaki T, Tanaka H. Vestibulo-Ocular Reflex Is Modulated by Noisy Galvanic Vestibular Stimulation. Front Neurol 2022; 13:826739. [PMID: 35250830 PMCID: PMC8893018 DOI: 10.3389/fneur.2022.826739] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 01/24/2022] [Indexed: 11/24/2022] Open
Abstract
We investigated whether noisy galvanic vestibular stimulation (nGVS) modulates the vestibulo-ocular reflex (VOR) and whether this effect is correlated with the effect of nGVS on body sway. Thirty healthy young adults participated. The video head impulse test (vHIT) was used to estimate the ratio of eye motion velocity/head motion velocity to VOR-gain. The gain 60 ms after the start of head motion (VOR-gain-60 ms) and regression slope (RS) (i.e., gain in eye and head motion; VOR-gain-RS) were calculated. The total path length of the foot center of pressure (COP-TL) during upright standing was calculated to estimate body sway. Noisy Galvanic Vestibular Stimulation at 0.2, 0.6, 1.2 mA, or sham stimulation (direct current: 0 mA) was delivered to the bilateral mastoid process in random order during vHIT and COP measurements. Application of nGVS at 0.2 mA significantly reduced VOR-gain-RS, while application of nGVS at 0.6 mA significantly increased COP-TL. Vestibulo-ocular reflex-gain-60 ms differed significantly between 0.2 and 1.2 mA. There was no significant correlation between COP-TL and VOR-related parameters. These findings suggest that nGVS at 0.2 mA inhibits the VOR, while nGVS at 0.6 mA increases body sway during upright standing, although there may be no relationship between the respective effects in healthy individuals.
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Affiliation(s)
- Akiyoshi Matsugi
- Faculty of Rehabilitation, Shijonawate Gakuen University, Daitou, Japan
- *Correspondence: Akiyoshi Matsugi
| | - Tomoyuki Shiozaki
- Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, Kashihara, Japan
| | - Hiroaki Tanaka
- Department of Physical Medicine and Rehabilitation, Kansai Medical University, Hirakata, Japan
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