Absence of Nonlinear Coupling Between Electric Vestibular Stimulation and Evoked Forces During Standing Balance

The vestibular system encodes motion and orientation of the head in space and is essential for negotiating in and interacting with the world. Recently, random waveform electric vestibular stimulation has become an increasingly common means of probing the vestibular system. However, many of the methods used to analyze the behavioral response to this type of stimulation assume a linear relationship between frequencies in the stimulus and its associated response. Here we examine this stimulus-response frequency linearity to determine the validity of this assumption. Forty-five university-aged subjects stood on a force-plate for 4 min while receiving vestibular stimulation. To determine the linearity of the stimulus-response relationship we calculated the cross-frequency power coupling between a 0 and 25 Hz bandwidth limited white noise stimulus and induced postural responses, as measured using the horizontal forces acting at the feet. Ultimately, we found that, on average, the postural response to a random stimulus is linear across stimulation frequencies. This result supports the use of analysis methods that depend on the assumption of stimulus-response frequency linearity, such as coherence and gain, which are commonly used to analyze the body’s response to random waveform electric stimuli.

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Effect of galvanic vestibular stimulation on human postural responses during support surface translations

Journal of Neurophysiology ◽

10.1152/jn.1995.73.2.896 ◽

1995 ◽

Vol 73 (2) ◽

pp. 896-901 ◽

Cited By ~ 80

Author(s):

J. T. Inglis ◽

C. L. Shupert ◽

F. Hlavacka ◽

F. B. Horak

Keyword(s):

Vestibular System ◽

Equilibrium Position ◽

Critical Role ◽

Vestibular Stimulation ◽

Galvanic Vestibular Stimulation ◽

Support Surface ◽

Quiet Stance ◽

Galvanic Current ◽

Postural Responses ◽

Platform Translation

1. We investigated the role of the vestibular system in postural control by combining galvanic vestibular stimulation (0.2-0.5 mA) with platform translations in standing subjects. Vestibular stimulation delivered 500 ms before and continuously during the platform translation produced little change in the earliest center of pressure (COP) and center of mass (COM) movements in response to platform translations, but resulted in large changes during the execution of the postural movement and in the final equilibrium position. 2. Vestibular stimulation produced anterior or posterior shifts in the position of COP and COM, depending on the polarity of the galvanic current. These shifts were larger during platform translations than during quiet stance. The peak of these shifts in COP and COM occurred at 1.5-2.5 s after the onset of platform translation, and increased in magnitude with increasing platform velocity. The final equilibrium positions of COP and COM were also shifted, but these shifts were smaller and not dependent on platform velocity. 3. These results imply that a tonic step of galvanic current to the vestibular system can change the final equilibrium position for an automatic postural response. Furthermore, these results indicate that the vestibular system may play a larger role in interpreting sensory reafference during postural movements, and especially during fast postural movements, than in controlling quiet stance. Finally, these results indicate that the vestibular system does not play a critical role in triggering the earliest postural responses, but it may be critical in establishing an internal reference for verticality.

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The effects of stochastic monopolar galvanic vestibular stimulation on human postural sway

Journal of Vestibular Research ◽

10.3233/ves-2003-122-303 ◽

2003 ◽

Vol 12 (2-3) ◽

pp. 77-85

Author(s):

Anthony P. Scinicariello ◽

J. Timothy Inglis ◽

J.J. Collins

Keyword(s):

Vestibular System ◽

Postural Sway ◽

Center Of Pressure ◽

Vestibular Stimulation ◽

Galvanic Vestibular Stimulation ◽

Lower Sensitivity ◽

Input Stimulus ◽

Vestibular Perception ◽

Afferent Nerve Endings ◽

Young Subjects

Galvanic vestibular stimulation (GVS) is a technique in which small currents are delivered transcutaneously to the afferent nerve endings of the vestibular system through electrodes placed over the mastoid bones. The applied current alters the firing rates of the peripheral vestibular afferents, causing a shift in a standing subject's vestibular perception and a corresponding postural sway. Previously, we showed that in subjects who are facing forward, stochastic bipolar binaural GVS leads to coherent stochastic mediolateral postural sway. The goal of this pilot study was to extend that work and to test the hypothesis that in subjects who are facing forward, stochastic monopolar binaural GVS leads to coherent stochastic anteroposterior postural sway. Stochastic monopolar binaural GVS was applied to ten healthy young subjects. Twenty-four trials, each containing a different galvanic input stimulus from among eight different frequency ranges, were conducted on each subject. Postural sway was evaluated through analysis of the center-of-pressure (COP) displacements under each subject's feet. Spectral analysis was performed on the galvanic stimuli and the COP displacement time series to calculate the coherence spectra. Significant coherence was found between the galvanic input signal and the anteroposterior COP displacement in some of the trials (i.e., at least one) in nine of the ten subjects. In general, the coherence values were highest for the mid-range frequencies that were tested, and lowest for the low- and high-range frequencies. However, the coherence values we obtained were lower than those we previously reported for stochastic bipolar binaural GVS and mediolateral sway. These differences may be due to fundamental characteristics of the vestibular system such as lower sensitivity to symmetric changes in afferent firing dynamics, and/or differences between the biomechanics of anteroposterior and mediolateral sway.

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Assessing head acceleration to identify a motor threshold to galvanic vestibular stimulation

Journal of Neurophysiology ◽

10.1152/jn.00254.2020 ◽

2021 ◽

Author(s):

Youstina Mikhail ◽

Jonathan Charron ◽

Jean-Marc Mac Thiong ◽

Dorothy Barthélemy

Keyword(s):

Center Of Pressure ◽

Vestibular Function ◽

Vestibular Stimulation ◽

Galvanic Vestibular Stimulation ◽

Head Acceleration ◽

Motor Threshold ◽

Recruitment Curve ◽

Eyes Closed ◽

Postural Responses ◽

Significant Difference

Galvanic vestibular stimulation (GVS) is used to assess vestibular function, but vestibular responses can exhibit variability depending on protocols or intensities used. We measured head acceleration in healthy subjects to identify an objective motor threshold on which to base GVS intensity when assessing postural responses. Thirteen healthy right-handed subjects stood on a force platform, eyes closed, head facing forward. An accelerometer was placed on the vertex to detect head acceleration, and electromyography activity of the right soleus was recorded. GVS (200 ms; current steps 0.5;1-4mA) was applied in a binaural and bipolar configuration. 1) GVS induced a biphasic accelerometer response at a latency of 15 ms. Based on response amplitude, we constructed a recruitment curve for all participants and determined the motor threshold. In parallel, the method of limits was used to devise a more rapid approach to determine motor threshold. 2) We observed significant differences between motor threshold based on therecruitment curve and perceptual thresholds (sensation/perception of movement). No significant difference was observed between the motor threshold based on the method of limits and perceptual thresholds . 3) Using orthogonal polynomial contrasts, we observed a linear progression between multiples of the objective motor threshold (0.5, 0.75, 1, 1.5x motor threshold) and the 95% confidence ellipse area, the first peak of center of pressure velocity, and the short and medium latency responses in the soleus. Hence, an objective motor threshold and a recruitment curve for GVS were determined based on head acceleration, which could increase understanding of the vestibular system.

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How the vestibular system interacts with somatosensory perception: A sham-controlled study with galvanic vestibular stimulation

Neuroscience Letters ◽

10.1016/j.neulet.2013.06.046 ◽

2013 ◽

Vol 550 ◽

pp. 35-40 ◽

Cited By ~ 37

Author(s):

Elisa R. Ferrè ◽

Brian L. Day ◽

Gabriella Bottini ◽

Patrick Haggard

Keyword(s):

Vestibular System ◽

Vestibular Stimulation ◽

Galvanic Vestibular Stimulation ◽

Controlled Study

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Effect of Eye-Object Distance on Body Sway during Galvanic Vestibular Stimulation

Brain Sciences ◽

10.3390/brainsci8110191 ◽

2018 ◽

Vol 8 (11) ◽

pp. 191 ◽

Cited By ~ 1

Author(s):

Osamu Aoki ◽

Yoshitaka Otani ◽

Shinichiro Morishita

Keyword(s):

Healthy Subjects ◽

Center Of Pressure ◽

Force Plate ◽

Distance Effect ◽

Vestibular Stimulation ◽

Galvanic Vestibular Stimulation ◽

Body Sway ◽

Mean Square ◽

Visual Condition ◽

Object Distance

Gazing at objects at a near distance (small eye-object distance) can reduce body sway. However, whether body sway is regulated by movement in the mediolateral or anteroposterior direction remains unclear. Galvanic vestibular stimulation (GVS) can induce body tilting in the mediolateral or anteroposterior direction. This study examined the directionality of the eye-object distance effect, using body-tilting GVS manipulations. Ten healthy subjects (aged 21.1 ± 0.3 years) stood on a force plate covered with a piece of foamed rubber and either closed their eyes or gazed at a marker located 0.5 m, 1.0 m, or 1.5 m in front of them. The GVS polarities were set to evoke rightward, forward, and backward body tilts. To compare the effects of eye-object distance in the mediolateral and anteroposterior directions, the root mean square (RMS) of the center of pressure (COP) without GVS was subtracted from the COP RMS during GVS. For swaying in the mediolateral direction, significant visual condition-related differences were found during rightward and forward GVS (p < 0.05). Thus, reductions in mediolateral body sway are more evident for smaller eye-object distances during rightward GVS. It would be appropriate to use body-tilting GVS to detect the directionality of the eye-object distance effect.

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Improvement in Automatic Postural Coordination Following Alexander Technique Lessons in a Person With Low Back Pain

Physical Therapy ◽

10.1093/ptj/85.6.565 ◽

2005 ◽

Vol 85 (6) ◽

pp. 565-578 ◽

Cited By ~ 36

Author(s):

Timothy W Cacciatore ◽

Fay B Horak ◽

Sharon M Henry

Keyword(s):

Low Back Pain ◽

Back Pain ◽

Force Plate ◽

Muscular Activity ◽

Alexander Technique ◽

Low Back ◽

Postural Coordination ◽

Postural Responses ◽

History Of ◽

Automatic Postural Responses

Abstract Background and Purpose. The relationship between abnormal postural coordination and back pain is unclear. The Alexander Technique (AT) aims to improve postural coordination by using conscious processes to alter automatic postural coordination and ongoing muscular activity, and it has been reported to reduce low back pain. This case report describes the use of the AT with a client with low back pain and the observed changes in automatic postural responses and back pain. Case Description. The client was a 49-year-old woman with a 25-year history of left-sided, idiopathic, lumbrosacral back pain. Automatic postural coordination was measured using a force plate during horizontal platform translations and one-legged standing. Outcomes. The client was tested monthly for 4 months before AT lessons and for 3 months after lessons. Before lessons, she consistently had laterally asymmetric automatic postural responses to translations. After AT lessons, the magnitude and asymmetry of her responses and balance improved and her low back pain decreased. Discussion. Further research is warranted to study whether AT lessons improve low back pain-associated abnormalities in automatic postural coordination and whether improving automatic postural coordination helps to reduce low back pain.

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Finding a Balance: A Systematic Review of the Biomechanical Effects of Vestibular Prostheses on Stability in Humans

Journal of Functional Morphology and Kinesiology ◽

10.3390/jfmk5020023 ◽

2020 ◽

Vol 5 (2) ◽

pp. 23

Author(s):

Felix Haxby ◽

Mohammad Akrami ◽

Reza Zamani

Keyword(s):

Vestibular System ◽

Postural Sway ◽

Vestibular Function ◽

Vestibular Stimulation ◽

Significant Heterogeneity ◽

Vestibular Loss ◽

Ocular Reflex ◽

Gait Characteristics ◽

Vestibulo Ocular Reflex ◽

Meta Analyses

The vestibular system is located in the inner ear and is responsible for maintaining balance in humans. Bilateral vestibular dysfunction (BVD) is a disorder that adversely affects vestibular function. This results in symptoms such as postural imbalance and vertigo, increasing the incidence of falls and worsening quality of life. Current therapeutic options are often ineffective, with a focus on symptom management. Artificial stimulation of the vestibular system, via a vestibular prosthesis, is a technique being explored to restore vestibular function. This review systematically searched for literature that reported the effect of artificial vestibular stimulation on human behaviours related to balance, using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) technique. A total of 21 papers matched the inclusion criteria of the literature search conducted using the PubMed and Web of Science databases (February 2019). The populations for these studies included both healthy adults and patients with BVD. In every paper, artificial vestibular stimulation caused an improvement in certain behaviours related to balance, although the extent of the effect varied greatly. Various behaviours were measured such as the vestibulo-ocular reflex, postural sway and certain gait characteristics. Two classes of prosthesis were evaluated and both showed a significant improvement in at least one aspect of balance-related behaviour in every paper included. No adverse effects were reported for prostheses using noisy galvanic vestibular stimulation, however, prosthetic implantation sometimes caused hearing or vestibular loss. Significant heterogeneity in methodology, study population and disease aetiology were observed. The present study confirms the feasibility of vestibular implants in humans for restoring balance in controlled conditions, but more research needs to be conducted to determine their effects on balance in non-clinical settings.

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