N. R. was supported by a research fund from Shahid Beheshti University of Medical Sciences and Health Services. S. G. S. was supported by NIDCD R03 DC015091 grant.

The data presented here and previously published3 were obtained by studies carried out in accordance with the recommendations of the Ethics Committee of Shahid Beheshti University of Medical Sciences, Tehran, Iran and a protocol that was approved by the Institutional Review Board of the University.
1. Participant screening and preparation
<ol>
	<li>Recruit participants who have had a history of balance problems for more than one year. 
	NOTE: Vestibular compensation happens most effectively over the first month after a lesion. The one year timepoint was chosen to provide enough time for natural compensation to reach its plateau and also ensure that the patient does not have a fluctuating vestibular disorder.</li>
	<li>Use the following exclusion criteria for patients:
	<ol>
		<li>History of central nervous system problems (e.g., head trauma, stroke, brain tumor, etc.) that may affect the central vestibular pathways, which are required for proper compensation.</li>
		<li>Diagnosed with a fluctuating vestibular disorder (e.g., benign paroxysmal positional vertigo [BPPV] or Meniere&#8217;s disease).</li>
		<li>Patients using other forms of vestibular rehabilitation or types of physical activity (e.g., athletes) that may improve vestibular compensation independent of the unidirectional rotation rehabilitation should be excluded. 
		NOTE: This criterion is suggested only for research purposes and to control for extraneous variables.</li>
	</ol>
	</li>
	<li>Do not limit participants based on age or gender. 
	NOTE: Similar to other compensation, this rehabilitation method is expected to have less pronounced effects in older subjects.</li>
	<li>Instruct participants to refrain from using any medications that suppress the central nervous system, including antihistamines or any anti-vertigo drugs for at least 1 day prior to each experimental session.</li>
	<li>Instruct participants not to use any nervous system stimulants, including amphetamines and caffeine for at least 1 day prior to each experimental session.</li>
	<li>Instruct participants to refrain from drinking alcoholic beverages in quantities that impair normal functioning, as this can interfere with functioning of the vestibular system and affect the results.</li>
</ol>
2. Measurement of the vestibulo-ocular reflex (VOR)
<ol>
	<li>Use either videonystagmography (VNG) or electronystagmography (ENG) to measure the VOR response during whole-body rotation. 
	NOTE: The data presented in the results section was recorded by ENG. The current equipment shown in the movie uses VNG.</li>
	<li>Perform all recordings in the dark, with the head positioned 30&#176; nose-down. 
	NOTE: For visualization purposes, the associated video is not performed in the dark.</li>
	<li>Ask participants to sit in the rotary chair, secure them in the chair with the harness, put the infrared goggles on, and fix the head in the headrest at a ~30&#176; nose-down position.</li>
	<li>After participants acclimate to the dark, calibrate the eye signal by asking them to look at laser targets that are projected on the wall at &#177;10&#176; angles (e.g., to the right, left, above, and below midline).</li>
	<li>Begin running the protocol once the eye tracker is calibrated accurately, when the subjects are ready.</li>
	<li>Keep subjects alert and distracted during all vestibular testing by asking them questions or having them do mental arithmetic (e.g., count backwards from 100).</li>
</ol>
3. Unidirectional rotation stimulus
<ol>
	<li>With the subject seated in the rotary chair, use a unidirectional rotation that consists of an asymmetric triangular velocity profile with an acceleration of 80&#176;/s2 over 4 s to reach a maximum velocity of 320&#176;/s, then slowly decelerate at 10&#176;/s2 to stop in about 30 s. 
	NOTE: The slow deceleration is particularly important in order to have a smooth stop in order to avoid stimulating the opposite side.</li>
	<li>Perform five such rotations with 1 min intervals. The five rotations together are considered a rehabilitation session (Figure 1B).</li>
	<li>Keep the subject in the chair after the last unidirectional rotation to test the symmetry with a bidirectional sinusoidal harmonic acceleration (SHA) rotation test at 40 min and 70 min post-unidirectional rotation. 
	NOTE: Keeping the patient in the chair will decrease the variability.</li>
	<li>Perform the SHA test using a wide range of sinusoidal rotations at frequencies of 0.05 Hz, 0.2 Hz, and 0.8 Hz, with a peak velocity of 60&#176;/s. 
	NOTE: For data presented in the results, a sinusoidal rotation at 0.2 Hz (40&#176;/s) was used for all evaluations.</li>
</ol>
4. Experiment design
<ol>
	<li>Evaluate subjects with a full battery of vestibular tests during the initial session (see below) in order to test VOR asymmetry and rule out any central problems.</li>
	<li>One week later, expose the subjects to the unidirectional rotation and an SHA test (steps 3.1&#8211;3.4).</li>
	<li>Repeat this process&#160;2x per week during the first 2 weeks, then 1x per week for the next 2 weeks (for a total of six sessions).</li>
	<li>Administer an SHA test at the beginning (step 3.4) and end (steps 3.3 and 3.4) of each session and calculate the directional preponderance (DP) as a measure of asymmetry: 
	<img alt="Equation" src="/files/ftp_upload/60053/60053eq1.jpg" /> 
	Where: VHR and VLR represent peak eye velocities during rotations toward the side with higher responses (HR) and lower responses (LR), respectively. 
	NOTE: The directional preponderance provides a normalized measure of the difference in peak eye velocity for rotations in the two directions. While it is mainly used for measuring asymmetry in caloric responses, it can be (and is) used for quantifying VOR asymmetry in SHA24,25,26,27,28.</li>
	<li>As the final session, perform another SHA test (step 3.4) 1 week after the last rehabilitation session.</li>
</ol>
5. Sessions details
<ol>
	<li>Initial session
	<ol>
		<li>During the first visit, take a brief history of the patient&#8217;s imbalance problems to verify the duration of vestibular asymmetry and ensure no indication of a fluctuating disorder.</li>
		<li>Perform a complete set of vestibular tests, including saccades, smooth pursuit, optokinetic, gaze holding, positional and positioning, caloric, and rotational tests.</li>
		<li>Only recruit patients with VOR asymmetry during rotation who have clear abnormal directional preponderance (DP), typically with asymmetry values of more than 10%. This will be considered the initial (baseline) DP for each subject. 
		NOTE: Different equipment might provide different normal ranges and it is best to use the range specified for your device or to base the normal range on lab-specific normative data.</li>
		<li>Clearly explain to the subjects the procedure of unidirectional rotation (5x in one session) and the total number of sessions (six times total).</li>
		<li>Ask subjects to sign a consent form that has been approved by the local Institutional Review Board (or equivalent, for experiments performed outside of the United States), while clearly informing them that they can drop out of the study at any point and for any reason.</li>
	</ol>
	</li>
	<li>Unidirectional rotation sessions (six sessions)
	<ol>
		<li>Expose subjects to the unidirectional rotation (steps 3.1&#8211;3.4) during six sessions (steps 4.3 and 4.4).</li>
		<li>At the beginning of each rehabilitation session, perform an SHA test (step 3.4) and calculate the DP value. 
		NOTE: This will provide the pre-rehabilitation DP for that session and long-term post-rehabilitation DP for the previous session.</li>
		<li>Do not perform the unidirectional rotational rehabilitation if the pre-rehabilitation DP value falls in the normal range (&#60;10%) in any of the sessions and instruct the subject to return for the next session.</li>
		<li>If the pre-rehabilitation DP is in the abnormal range, wait 5 min after the SHA test and perform the unidirectional rotational rehabilitation.</li>
		<li>Perform a second SHA test 40 min and 70 min after the end of unidirectional rotation rehabilitation (step 3.4) and calculate the post-rehabilitation DP for this session.</li>
		<li>Instruct the subjects to return for the next session.</li>
	</ol>
	</li>
	<li>Final session (week seven)
	<ol>
		<li>Perform an SHA test only (step 3.4) and calculate the DP value. 
		NOTE: This will serve as the final asymmetry measurement.</li>
		<li>Do not use unidirectional rotation in this&#160;session.</li>
	</ol>
	</li>
</ol>

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L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rehabilitation+outcome+in+home-based+versus+supervised+exercise+programs+for+chronically+dizzy+patients.">Rehabilitation outcome in home-based versus supervised exercise programs for chronically dizzy patients.</a> Archives of Gerontology and Geriatrics. 51 (3), 264-267 (2010).</li><li>Topuz, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficacy+of+vestibular+rehabilitation+on+chronic+unilateral+vestibular+dysfunction.">Efficacy of vestibular rehabilitation on chronic unilateral vestibular dysfunction.</a> Clinical Rehabilitation. 18 (1), 76-83 (2004).</li><li>Black, F. O., Pesznecker, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vestibular+adaptation+and+rehabilitation.">Vestibular adaptation and rehabilitation.</a> Current Opinion in Otolaryngological Head and Neck Surgery. 11 (5), 355-360 (2003).</li></ol>

The authors have nothing to disclose.

The rehabilitation method presented here consists of repeated unidirectional rotations in the dark toward the less responsive (LR) side in patients with vestibular imbalance and VOR asymmetry. Most rehabilitation techniques enhance multisensory integration in order to improve balance16,17,18,19,20. The method presented here targets the vestibular pathway, and ...

Vestibular dysfunction is a common disorder with a prevalence of ~35% in adults above 40 years old1. Most vestibular disorders result in an asymmetry between input from both sides, resulting in an illusion of rotation called vertigo. In the absence of normal vestibular function, even simple daily activities can be challenging. Vestibular dysfunction is often quantified by the vestibulo-ocular reflex (VOR). During natural activities, such as walking or running, the VOR moves the eyes in the opposite direction&#160;and with the same velocity as head movement. This reflex has a short latency of ~5 ms, and it is mediated in the horizontal plane through a simple, three-neuron arc2. The information travels from vestibular receptors to the vestibular nuclei, then to the abducens motor neurons. These eye movements result in stabilization of horizontal gaze during daily activities. The symmetry of the VOR in response to clockwise and counterclockwise rotations is an important test of vestibular function.
Unilateral vestibular dysfunction produces central compensatory changes and centrally driven peripheral changes to overcome defective asymmetric VOR and resulting vestibular imbalance. Even after permanent vestibular lesions, such as a unilateral vestibular neurectomy, the vertigo and accompanying symptoms improve over a short period (days to weeks) of time. Due to this ability, the vestibular system has been a model for studying adaptation and compensation in neural pathways. It has been previously shown3 that changes in central vestibular pathways can be implemented by a unidirectional rotation based on a hypothesis proposed by one of the authors (N.R.) about 20 years ago. Other studies have also shown compensatory changes in different parts of the sensory pathway, including the vestibular nuclei (VN)4,5,6,7,8, commissural pathways between the VN on both sides9, cerebellar inputs10, and the vestibular periphery11. These compensatory changes result in a new balance in the activity of VN neurons on both sides.
Despite the impressive ability of the vestibular system to compensate for asymmetric inputs from the two ears, research has shown that responses to fast movements are never fully compensated12,13. It is now known that natural vestibular compensation does not use the full capacity of the system, and the compensated VOR response can be improved in animals that have participated in visual-vestibular training14,15. It has long been known that vestibular rehabilitation exercises improve the compensation in patients with chronic imbalance problems by enhancing the (non-vestibular) multisensory nature of balance control16,17,18,19,20,21. The goal of these vestibular rehabilitation exercises is to use physiological or behavioral approaches to improve symptoms as well as a patient&#39;s quality of life and independence22,23.
Described herein is a rehabilitation method that uses unidirectional rotations toward the &#34;weaker&#34; side (Figure 1A). The basic idea for this method comes from Hebbian plasticity, in which neural connections become stronger when they are stimulated. This method specifically modifies vestibular inputs rather than enhancing multisensory integration, which is the basis for other vestibular rehabilitation exercises. Previous research has shown that unidirectional rotations decreases VOR asymmetry in 1-2 sessions in patients with unilateral vestibular dysfunction3. This effect was mainly due to an increase in the activity of the side with a lower response (LR), as well as a slight decrease in the activity of the side with a higher response (HR). This change is most likely mediated by modifications in the central pathways (e.g., strengthening of afferent pathways, such as VN connections or changes in commissural inputs). In effect, this technique may be used as a supervised method for vestibular rehabilitation in those with longstanding vestibular asymmetry.

<table><tbody><tr><td>VEST operating and analysis software</td><td>NeuroKinetics</td><td></td><td></td></tr><tr><td>Electronystagmograph</td><td>Nicolet</td><td>Spirit Model 1992</td><td>Equipment used for collecting the data presented in the Results section</td></tr><tr><td>I-Portal NOTC (Neurotologic Test Center)</td><td>NeuroKinetics</td><td></td><td>Equipment shown for current studies and shown in the movie</td></tr></tbody></table>

using unidirectional rotations to improve vestibular system asymmetry in patients with vestibular dysfunction

The vestibular system provides information about head movement and mediates reflexes that contribute to balance control and gaze stabilization during daily activities. Vestibular sensors are located in the inner ear on both sides of the head and project to the vestibular nuclei in the brainstem. Vestibular dysfunction is often due to an asymmetry between input from the two sides. This results in asymmetrical neural inputs from the two ears, which can produce an illusion of rotation, manifested as vertigo. The vestibular system has an impressive capacity for compensation, which serves to rebalance how asymmetrical information from the sensory end organs on both sides is processed at the central level. To promote compensation, various rehabilitation programs are used in the clinic; however, they primarily use exercises that improve multisensory integration. Recently, visual-vestibular training has also been used to improve the vestibulo-ocular reflex (VOR) in animals with compensated unilateral lesions. Here, a new method is introduced for rebalancing the vestibular activity on both sides in human subjects. This method consists of five unidirectional rotations in the dark (peak velocity of 320&#176;/s) toward the weaker side. The efficacy of this method was shown in a sequential, double-blinded clinical trial in 16 patients with VOR asymmetry (measured by the directional preponderance in response to sinusoidal rotations). In most cases, VOR asymmetry decreased after a single session, reached normal values within the first two sessions in one week, and the effects lasted up to 6 weeks. The rebalancing effect is due to both an increase in VOR response from the weaker side and a decrease in response from the stronger side. The findings suggest that unidirectional rotation can be used as a supervised rehabilitation method to reduce VOR asymmetry in patients with longstanding vestibular dysfunction.

Short-term effects of the unidirectional rotation were evaluated by measuring the VOR with a 0.2 Hz (40&#176;/s) sinusoidal rotation test at 70 min after rehabilitation3. Figure 2 shows the peak eye velocities during the VOR responses to rotations in the two directions (Figure 2A) and the change in the DP (Figure 2B). Following unidirectional rotation, the response to rotation...

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Using Unidirectional Rotations to Improve Vestibular System Asymmetry in Patients with Vestibular Dysfunction

A new rehabilitation method is presented for rebalancing the vestibular system in patients with asymmetric responses, which consists of unidirectional rotations toward the weaker side. By directly modifying the vestibular pathway rather than enhancing the multisensory aspects of compensation, asymmetry can be normalized within 1-2 sessions and show lasting effects.

The vestibular system provides information about head movement and mediates reflexes that contribute to balance control and gaze stabilization during ...

using-unidirectional-rotations-to-improve-vestibular-system-asymmetry

Research

JoVE Journal

Behavior

7.1K Views.  Shahid Beheshti University of Medical Sciences and Health Services. Het stimuleren van de zwakkere kant en het remmen van de sterkere kant, een idee oorspronkelijk voorgesteld door Doctor Nayer Rassaian, is aangetoond dat assymetrie afnemen bij personen met vestibulaire onbalans. Deze techniek biedt een unieke methode voor het effectief stimuleren van het vestibulaire systeem in het donker en vereist geen ingewikkelde apparatuur. Unidirectionele rotatie kan worden gebruikt als een revalidatieoptie voor patiënten met een onbalans tussen vestibulaire ingangen ...

Video: Using Unidirectional Rotations to Improve Vestibular System Asymmetry in Patients with Vestibular Dysfunction

Behavioral Assessment of the Aging Mouse Vestibular System

Age related decline in balance performance is associated with deteriorating muscle strength, motor coordination and vestibular function. While a number of studies show changes in balance phenotype with age in rodents, very few isolate the vestibular contribution to balance under either normal conditions or during senescence. We use two standard behavioral tests to characterize the balance performance of mice at defined age points over the lifespan: the rotarod test and the inclined balance beam test. Importantly though, a custom built rotator is also used to stimulate the vestibular system of mice (without inducing overt signs of motion sickness). These two tests have been used to show that changes in vestibular mediated-balance performance are present over the murine lifespan. Preliminary results show that both the rotarod test and the modified balance beam test can be used to identify changes in balance performance during aging as an alternative to more difficult and invasive techniques such as vestibulo-ocular (VOR) measurements.

Motor control and balance performance are known to deteriorate with age. This paper presents a number of standard noninvasive behavioral tests with the addition of a simple rotary stimulus to challenge the vestibular system and show changes in balance performance in a murine model of aging.

Age related decline in balance performance is associated with deteriorating muscle strength, motor coordination and vestibular function. While a number of ...

Three Dimensional Vestibular Ocular Reflex Testing Using a Six Degrees of Freedom Motion Platform

The vestibular organ is a sensor that measures angular and linear accelerations with six degrees of freedom (6DF). Complete or partial defects in the vestibular organ results in mild to severe equilibrium problems, such as vertigo, dizziness, oscillopsia, gait unsteadiness nausea and/or vomiting. A good and frequently used measure to quantify gaze stabilization is the gain, which is defined as the magnitude of compensatory eye movements with respect to imposed head movements. To test vestibular function more fully one has to realize that 3D VOR ideally generates compensatory ocular rotations not only with a magnitude (gain) equal and opposite to the head rotation but also about an axis that is co-linear with the head rotation axis (alignment). Abnormal vestibular function thus results in changes in gain and changes in alignment of the 3D VOR response.
Here we describe a method to measure 3D VOR using whole body rotation on a 6DF motion platform. Although the method also allows testing translation VOR responses 1, we limit ourselves to a discussion of the method to measure 3D angular VOR. In addition, we restrict ourselves here to description of data collected in healthy subjects in response to angular sinusoidal and impulse stimulation.
Subjects are sitting upright and receive whole-body small amplitude sinusoidal and constant acceleration impulses. Sinusoidal stimuli (f = 1 Hz, A = 4&deg;) were delivered about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5&deg; in azimuth. Impulses were delivered in yaw, roll and pitch and in the vertical canal planes. Eye movements were measured using the scleral search coil technique 2. Search coil signals were sampled at a frequency of 1 kHz.
The input-output ratio (gain) and misalignment (co-linearity) of the 3D VOR were calculated from the eye coil signals 3.
Gain and co-linearity of 3D VOR depended on the orientation of the stimulus axis. Systematic deviations were found in particular during horizontal axis stimulation. In the light the eye rotation axis was properly aligned with the stimulus axis at orientations 0&deg; and 90&deg; azimuth, but gradually deviated more and more towards 45&deg; azimuth.
The systematic deviations in misalignment for intermediate axes can be explained by a low gain for torsion (X-axis or roll-axis rotation) and a high gain for vertical eye movements (Y-axis or pitch-axis rotation (see Figure 2). Because intermediate axis stimulation leads a compensatory response based on vector summation of the individual eye rotation components, the net response axis will deviate because the gain for X- and Y-axis are different.
In darkness the gain of all eye rotation components had lower values. The result was that the misalignment in darkness and for impulses had different peaks and troughs than in the light: its minimum value was reached for pitch axis stimulation and its maximum for roll axis stimulation.
Case Presentation
Nine subjects participated in the experiment. All subjects gave their informed consent. The experimental procedure was approved by the Medical Ethics Committee of Erasmus University Medical Center and adhered to the Declaration of Helsinki for research involving human subjects.
Six subjects served as controls. Three subjects had a unilateral vestibular impairment due to a vestibular schwannoma. The age of control subjects (six males and three females) ranged from 22 to 55 years. None of the controls had visual or vestibular complaints due to neurological, cardio vascular and ophthalmic disorders.
The age of the patients with schwannoma varied between 44 and 64 years (two males and one female). All schwannoma subjects were under medical surveillance and/or had received treatment by a multidisciplinary team consisting of an othorhinolaryngologist and a neurosurgeon of the Erasmus University Medical Center. Tested patients all had a right side vestibular schwannoma and underwent a wait and watch policy (Table 1; subjects N1-N3) after being diagnosed with vestibular schwannoma. Their tumors had been stabile for over 8-10 years on magnetic resonance imaging.

A method is described to measure three-dimensional vestibulo ocular reflexes (3D VOR) in humans using a six degrees of freedom (6DF) motion simulator. The gain and misalignment of the 3D angular VOR provide a direct measure of the quality of vestibular function. Representative data on healthy subjects are provided

The vestibular organ is a sensor that measures angular and linear accelerations with six degrees of freedom (6DF). Complete or partial defects in the ...

Neuroscience

A Vibrotactile Feedback Device for Seated Balance Assessment and Training

Postural perturbations, motion tracking, and sensory feedback are modern techniques used to challenge, assess, and train upright sitting, respectively. The goal of the developed protocol is to construct and operate a sitting platform that can be passively destabilized while an inertial measurement unit quantifies its motion and vibrating elements deliver tactile feedback to the user. Interchangeable seat attachments alter the stability level of the device to safely challenge sitting balance. A built-in microcontroller allows fine-tuning of the feedback parameters to augment sensory function. Posturographic measures, typical of balance assessment protocols, summarize the motion signals acquired during timed balance trials. No dynamic sitting protocol to date provides variable challenge, quantification, and sensory feedback free of laboratory constraints. Our results demonstrate that non-disabled users of the device exhibit significant changes in posturographic measures when balance difficulty is altered or vibrational feedback provided. The portable, versatile device has potential applications in rehabilitation (following skeletal, muscular, or neurological injury), training (for sports or spatial awareness), entertainment (via virtual or augmented reality), and research (of sitting-related disorders).

A sitting platform has been developed and assembled that passively destabilizes sitting posture in humans. During the user&#39;s stabilizing task, an inertial measurement unit records the device&#39;s motion, and vibrating elements deliver performance-based feedback to the seat. The portable, versatile device may be used in rehabilitation, assessment, and training paradigms.

Postural perturbations, motion tracking, and sensory feedback are modern techniques used to challenge, assess, and train upright sitting, respectively. ...

Assessing the Autonomic and Behavioral Effects of Passive Motion in Rats using Elevator Vertical Motion and Ferris-Wheel Rotation

The overall goal of this study is to assess the autonomic and behavioral effects of passive motion in rodents using the elevator vertical motion and Ferris-wheel rotation devices. These assays can help confirm the integrity and normal functioning of the autonomic nervous system. They are coupled to quantitative measures based on defecation counting, open-field examination, and balance beam crossing. The advantages of these assays are their simplicity, reproducibility, and quantitative behavioral measures. The limitations of these assays are that the autonomic reactions could be epiphenomena of non-vestibular disorders and that a functioning vestibular system is required. Examination of disorders such as motion sickness will be greatly aided by the detailed procedures of these assays.

Protocols are presented to assess the autonomic and behavioral effects of passive motion in rodents using elevator vertical motion and Ferris-wheel rotation.

The overall goal of this study is to assess the autonomic and behavioral effects of passive motion in rodents using the elevator vertical motion and ...

Controlled Rotation of Human Observers in a Virtual Reality Environment

The low cost and availability of Virtual Reality (VR) systems have supported a recent acceleration of research into perception and behavior under more naturalistic, multisensory, and immersive conditions. One area of research that has particularly benefited from the use of VR systems is multisensory integration, for example, the integration of visual and vestibular cues to give rise to a sense of self-motion. For this reason, an accessible method for the controlled physical rotation of an observer in a virtual environment represents a useful innovation. This paper presents a method for automating the rotation of an office swivel chair along with a method for integrating that motion into a VR experience. Using an example experiment, it is demonstrated that the physical motion, thus produced, is integrated with the visual experience of an observer in a way consistent with expectations; high integration when the motion is congruent with the visual stimulus and low integration when the motion is incongruent.

The controlled physical rotation of a human observer is desirable for certain experimental, recreational, and educational applications. This paper outlines a method for converting an office swivel chair into a medium for controlled physical rotation in a virtual reality environment.

The low cost and availability of Virtual Reality (VR) systems have supported a recent acceleration of research into perception and behavior under more ...

Estimating Vestibular Perceptual Thresholds Using a Six-Degree-Of-Freedom Motion Platform

Vestibular perceptual thresholds refer to the motion intensity required to enable a participant to detect or discriminate a motion based on vestibular input. Using passive motion profiles provided by six degree-of-motion platforms, vestibular perceptual thresholds can be estimated for any kind of motion and thereby target each of the sub-components of the vestibular end-organ. Assessments of vestibular thresholds are clinically relevant as they complement diagnostic tools such as caloric irrigation, the head impulse test (HIT), or vestibular evoked myogenic potentials (VEMPs), which only provide information on sub-components of the vestibular system, but none of them allow for assessing all components. There are several methods with different advantages and disadvantages for estimating vestibular perceptual thresholds. In this article, we present a protocol using an adaptive staircase algorithm and sinusoidal motion profiles for an efficient estimation procedure. Adaptive staircase algorithms consider the response history to determine the peak velocity of the next stimuli and are the most commonly used algorithms in the vestibular domain. We further discuss the impact of motion frequency on vestibular perceptual thresholds.

In this article, we describe the methods, procedures, and technologies required to estimate vestibular perceptual thresholds using a six-degree-of-freedom motion platform.

Vestibular perceptual thresholds refer to the motion intensity required to enable a participant to detect or discriminate a motion based on vestibular ...

Implementing Vestibular Disorder Screening Tests

Screening People on Standing Balance with Romberg Testing and Walking Balance with Tandem Walking

The goal of this protocol is to inform readers about the exact procedures to use to perform two screening tests for vestibular disorders: tandem walking (TW) with eyes closed, also known as heel-toe walking, and the Clinical Test of Sensory Integration and Balance (CTSIB), which is also known as the modified Romberg. The study describes the steps for performing each test and each of the three CTSIB subtests so that the reader will be able to replicate the test conditions for use in the clinic, in the clinical laboratory, or in any other situation needing valid and reliable screening for balance skill which might be affected by changes in vestibular system function. The procedures detailed here can be easily administered and take less than 1 min per trial. References to published papers with normative data are provided. The representative results section includes examples of data collected with these screening tests.

Author Spotlight: Developing Low-Tech Balance Assessment Methods for Broad-Spectrum Healthcare Applications 

This article describes procedures for screening people for standing and walking balance impairments using two normed, rapid, low-tech balance tests.

The goal of this protocol is to inform readers about the exact procedures to use to perform two screening tests for vestibular disorders: tandem walking ...

Surgical Labyrinthectomy of the Rat to Study the Vestibular System

To study the vestibular system or the vestibular compensation process, a number of methods have been developed to cause vestibular damage, including surgical or chemical labyrinthectomy and vestibular neurectomy. Surgical labyrinthectomy is a relatively simple, reliable, and rapid method. Here, we describe the surgical technique for rat labyrinthectomy. A postauricular incision is made under general anesthesia to expose the external auditory canal and the tympanic membrane, after which the tympanic membrane and the ossicles are removed without the stapes. The stapes artery, which is located between the stapes and the oval window, is a vulnerable structure and must be preserved to obtain a clear surgical field. A hole to fenestrate the vestibule is made with a 2.1-mm drill bur superior to the stapes. Then, 100% ethanol is injected through this hole and aspirated several times. Meticulous dissection under a microscope and careful bleeding control are essential to obtain reliable results. Symptoms of vestibular loss, such as nystagmus, head tilting, and a rolling motion, are seen immediately after surgery. The rotarod or rotation chair test can be used to objectively and quantitatively evaluate the vestibular function.

This protocol describes the surgical labyrinthectomy of a rat, which is a useful method for studying the vestibular system.

To study the vestibular system or the vestibular compensation process, a number of methods have been developed to cause vestibular damage, including ...

Medicine

Stochastic Noise Application for the Assessment of Medial Vestibular Nucleus Neuron Sensitivity In Vitro

Galvanic vestibular stimulation (GVS) has been shown to improve balance measures in individuals with balance or vestibular impairments. This is proposed to be due to the stochastic resonance (SR) phenomenon, which is defined as application of a low-level/subthreshold stimulus to a non-linear system to increase detection of weaker signals. However, it is still unknown how SR exhibits its positive effects on human balance. This is one of the first demonstrations of the effects of sinusoidal and stochastic noise on individual neurons. Using whole-cell patch clamp electrophysiology, sinusoidal and stochastic noise can be applied directly to individual neurons in the medial vestibular nucleus (MVN) of C57BL/6 mice. Here we demonstrate how to determine the threshold of MVN neurons in order to ensure the sinusoidal and stochastic stimuli are subthreshold and from this, determine the effects that each type of noise has on MVN neuronal gain. We show that subthreshold sinusoidal and stochastic noise can modulate the sensitivity of individual neurons in the MVN without affecting basal firing rates.

Galvanic vestibular stimulation in humans exhibits improvements in vestibular function. However, it is unknown how these effects occur. Here, we describe how to apply sinusoidal and stochastic electrical noise and evaluate appropriate stimulus amplitudes in individual medial vestibular nucleus neurons in the C57BL/6 mouse.

Galvanic vestibular stimulation (GVS) has been shown to improve balance measures in individuals with balance or vestibular impairments. This is proposed ...

Assessment of Static Graviceptive Perception in the Roll-Plane using the Subjective Visual Vertical Paradigm

Vestibular disorders are among the most common syndromes in medicine. In recent years, new vestibular diagnostic systems have been introduced that allow the examination of all semicircular canals in the clinical setting. Assessment methods of the otolithic system, which is responsible for the perception of linear acceleration and perception of gravity, are far less in clinical use. There are several experimental approaches for measuring the perception of gravity. The most frequently used method is the determination of the subjective visual vertical. This is usually measured with the head in an upright position. We present here an assessment method for testing otolith function in the roll plane. The subjective visual vertical is measured in the head upright position as well as with head inclination of &#177; 15&#176; and &#177; 30&#176; in the roll plane. This extended functional paradigm is an easy-to-perform clinical test of otolith function and ensures increased information content for the detection of impaired graviceptive perception.

The perception of gravity is commonly determined by the subjective visual vertical in the head upright position. The additional assessment at head tilts of &#177; 15&#176; and &#177; 30&#176; in the roll plane ensures increased information content for the detection of impaired graviceptive perception.

Vestibular disorders are among the most common syndromes in medicine. In recent years, new vestibular diagnostic systems have been introduced that allow ...

Using Unidirectional Rotations to Improve Vestibular System Asymmetry in Patients with Vestibular Dysfunction

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