Human Vestibular System Research Articles

Electrical Vestibular Stimuli Evoke Robust Muscle Activity in Deep and Superficial Neck Muscles in Humans.

Neck muscle activity evoked by vestibular stimuli is a clinical measure for evaluating the function of the vestibular apparatus. Cervical vestibular-evoked myogenic potentials (cVEMP) are most commonly measured in the sternocleidomastoid muscle (and more recently the splenius capitis muscle) in response to air-conducted sound, bone-conducted vibration or electrical vestibular stimuli. It is currently unknown, however, whether and how other neck muscles respond to vestibular stimuli. Here we measured activity bilaterally in the sternocleidomastoid, splenius capitis, sternohyoid, semispinalis capitis, multifidus, rectus capitis posterior, and obliquus capitis inferior using indwelling electrodes in two subjects exposed to binaural bipolar electrical vestibular stimuli. All recorded neck muscles responded to the electrical vestibular stimuli (0–100 Hz) provided they were active. Furthermore, the evoked responses were inverted on either side of the neck, consistent with a coordinated contribution of all left-right muscle pairs acting as antagonists in response to the electrically-evoked vestibular error of head motion. Overall, our results suggest that, as previously observed in cat neck muscles, broad connections exist between the human vestibular system and neck motoneurons and highlight the need for future investigations to establish their neural connections.

Effect of visual field motion on vestibulo-myogenic response during upright stance: A pilot study

Effect of visual field motion on vestibulo-myogenic response during upright stance: A pilot study

Stochastic resonance in the human vestibular system – Noise-induced facilitation of vestibulospinal reflexes

BackgroundThere is strong evidence that the presence of noise can enhance information processing in sensory systems via stochastic resonance (SR). ObjectivesTo examine the presence of SR in human vestibulospinal reflex function. MethodsHealthy subjects were stimulated with 1 Hz sinusoidal GVS of varying amplitudes (0–1.9 mA). Coherence between GVS input and stimulation-induced motion responses was determined and psychometric function fits were subsequently used to determine individual vestibulospinal reflex thresholds. This procedure was repeated with additional application of imperceptible white noise GVS (nGVS). ResultsnGVS significantly facilitated the detectability of weak subthreshold vestibular inputs (p < 0.001) and thereby effectively lowered the vestibulospinal threshold in 90% of participants (p < 0.001, mean reduction: 17.5 ± 14.6%). ConclusionThis finding provides evidence for the presence of SR-dynamics in the human vestibular system and gives a functional explanation for previously observed ameliorating effects of low-intensity vestibular noise stimulation on balance control in healthy subjects and patients with vestibular hypofunction.

8 Cognitive and psychiatric comorbidities in patients with vestibular disorder

Objective It is becoming increasingly clear from a variety of clinical and laboratory approaches that the human vestibular system not only regulates autonomic activity but also influences higher level processes. To help understand the nature of these higher-level interactions, we investigated the prevalence of cognitive, psychiatric and fatigue disturbances in a sample of 100 patients with primary vestibular disorder. The nature of this relationship and the variables influencing it were also explored. Method A comprehensive neuropsychological assessment battery, including measures of depression, anxiety, depersonalization, fatigue, sleep, memory, attention and executive function was completed by patients at their initial neuro-otology appointment. Neurological questionnaires and balance function tests were also administered. Results Unexpectedly, nearly all patients showed evidence of clinical impairment on most tests. Symptoms of fatigue, anxiety and working memory impairment were especially prevalent in the sample (over 50% fell outside the normative cut-off). Age, visual dominance, and previous access of psychological support were all significant predictors of the presence of these comorbidities. Conclusion These finding suggest that the vestibular system exerts a much wider influence on cognition and affect than previously indicated, and underlines the need for broader clinical diagnosis, assessment and management in patients who present with balance complaints.

What the electrical impedance can tell about the intrinsic properties of an electrodynamic shaker.

Small electrodynamic shakers are becoming increasingly popular for diagnostic investigations of the human vestibular system. More specifically, they are used as mechanical stimulators for eliciting a vestibular evoked myogenic potential (VEMP). However, it is largely unknown how shakers perform under typical measurement conditions, which considerably differ from the normal use of a shaker. Here, it is shown how the basic properties of a shaker can be determined without requiring special sensors such as accelerometers or force gauges. In essence, the mechanical parts of the shaker leave a signature in the electrical impedance, and an interpretation of this signature using a simple model allows for drawing conclusions about the properties of the shaker. The theory developed (which is quite general so that it is usable also in other contexts) is applied to experimental data obtained for the minishaker commonly used in VEMP measurements. It is shown that the experimental conditions substantially influence the properties of the shaker. Relevant factors are, in particular, the spatial orientation of the shaker (upright, horizontal or upside-down) and the static force acting on the table of the shaker (which in a real measurement corresponds to the force by which the shaker is pressed against the test person’s head). These results underline the desirability of a proper standardization of VEMP measurements. Direct measurements of displacement and acceleration prove the consistency of the conclusions derived from the electrical impedance.

Semicircular canal modeling in human perception.

The human vestibular system is a sensory and equilibrium system that manages and controls the human sense of balance and movement. It is the main sensor humans use to perceive rotational and linear motions. Determining an accurate mathematical model of the human vestibular system is significant for research pertaining to motion perception, as the quality and effectiveness of the motion cueing algorithm (MCA) directly depends on the mathematical model used in its design. This paper describes the history and analyses the development process of mathematical semicircular canal models. The aim of this review is to determine the most consistent and reliable mathematical semicircular canal models that agree with experimental results and theoretical analyses, and offer reliable approximations for the semicircular canal functions based on the existing studies. Selecting and formulating accurate mathematical models of semicircular canals are essential for implementation into the MCA and for ensuring effective human motion perception modeling.

Peripheral vestibular pathology in Mondini dysplasia.

In this study, our objective was to histopathologically analyze the peripheral vestibular system in patients with Mondini dysplasia. Comparative human temporal bone study. We assessed the sensory epithelium of the human vestibular system with a focus on the number of type I and type II hair cells, as well as the total number of hair cells. We compared those numbers in our Mondini dysplasia group versus our control group. The loss of type I and type II hair cells in the cristae of the superior, lateral, and posterior semicircular canals, as well as in the saccular and utricular macula, was significantly higher in our Mondini dysplasia group than in our control group. The total number of hair cells significantly decreased in the cristae of the superior, lateral, and posterior semicircular canals, as well as in the saccular and utricular macula, in our Mondini dysplasia group. Loss of vestibular hair cells can lead to vestibular dysfunction in patients with Mondini dysplasia. NA Laryngoscope, 127:206-209, 2017.

Visual-vestibular processing in the human Sylvian fissure.

Unlike other sensory systems, the cortical organization of the human vestibular system is not well established. A central role is assumed for the region of the posterior Sylvian fissure, close to the posterior insula. At this site, activation during vestibular stimulation has been observed in previous imaging studies and labeled as the parieto-insular vestibular cortex area (PIVC). However, vestibular responses are found in other parts of the Sylvian fissure as well, including a region that is referred to as the posterior insular cortex (PIC). The anatomical and functional relationship between PIC and PIVC is still poorly understood, because both areas have never been compared in the same participants. Therefore, to better understand the apparently more complex organization of vestibular cortex in the Sylvian fissure, we employed caloric and visual object motion stimuli during functional magnetic resonance imaging and compared location and function of PIVC and PIC in the same participants. Both regions responded to caloric vestibular stimulation, but only the activation pattern in right PIVC reliably represented the direction of the caloric stimulus. Conversely, activity in PIVC was suppressed during stimulation with visual object motion, whereas PIC showed activation. Area PIC is located at a more posterior site in the Sylvian fissure than PIVC. Our results suggest that PIVC and PIC should be considered separate areas in the vestibular Sylvian network, both in terms of location and function.

Impact of electromagnetic fields on human vestibular system and standing balance: pilot results and future developments

Although studies have found that extremely low-frequency (ELF, < 300 Hz) magnetic fields (MF) can modulate human standing balance, the acute effects of electromagnetic fields on standing balance have not been systematically investigated. This work aims to establish the threshold for acute standing balance modulation during ELFMF exposure. One hundred volunteers will be exposed to transcranial electric stimulations (Direct Current - DC and Alternating Current - AC, 1 mA) and ELFMF (0 to 160 Hz, 0 to 100 mT). The displacement of their center of pressure will be collected and analyzed as an indicator of vestibular performance. During pilot testing (n=6), we found increased lateral sway with DC, and to a lesser extent, AC exposure. The ELFMF exposure system still needs to be adapted to allow meaningful results. Future protocol design will test for possible effects due to exposures in the radiofrequency range (i.e. above 3 kHz). These results will contribute to the literature documenting exposure guidelines aiming to protect workers and the general public.

Computational approach to assess postural tests under microgravity conditions

Human vestibular system is extremely fragile and rapidly degrades when gravity is significantly lower than the gravity of Earth. Unfortunately, current balance assessment tools, including state-of-start computerized centre-of-mass measurement platforms, cannot be used in space because of the low gravity. Thus, a problem of developing new methods to assess postural stability under microgravity conditions is very important. This paper describes a distance-based criterion to estimate multidimensional measurements and its application for postural tests assessment. It has been shown that proposed criterion may be effectively used to estimate the equilibrium function by means of low-end hardware, which does not rely on the gravitational force. The criterion was compared against several known indexes and its ability to distinguish disorders of the balance has been studied.

Aging of the Human Vestibular System.

Aging affects every sensory system in the body, including the vestibular system. Although its impact is often difficult to quantify, the deleterious impact of aging on the vestibular system is serious both medically and economically. The deterioration of the vestibular sensory end organs has been known since the 1970s; however, the measurable impact from these anatomical changes remains elusive. Tests of vestibular function either fall short in their ability to quantify such anatomical deterioration, or they are insensitive to the associated physiologic decline and/or central compensatory mechanisms that accompany the vestibular aging process. When compared with healthy younger individuals, a paucity of subtle differences in test results has been reported in the healthy older population, and those differences are often observed only in response to nontraditional and/or more robust stimuli. In addition, the reported differences are often clinically insignificant insomuch that the recorded physiologic responses from the elderly often fall within the wide normative response ranges identified for normal healthy adults. The damaging economic impact of such vestibular sensory decline manifests itself in an exponential increase in geriatric dizziness and a subsequent higher prevalence of injurious falls. An estimated $10 to $20 billion dollar annual cost has been reported to be associated with falls-related injuries and is the sixth leading cause of death in the elderly population, with a 20% mortality rate. With an estimated 115% increase in the geriatric population over 65 years of age by the year 2050, the number of balanced-disordered patients with a declining vestibular system is certain to reach near epidemic proportions. An understanding of the effects of age on the vestibular system is imperative if clinicians are to better manage elderly patients with balance disorders, dizziness, and vestibular disease.

A New Approach for Body Balance of a Humanoid Robot

In humans, the vestibular system along with other sensory and motor systems is responsible for three cognitive functions that support mobility. First, is responsible for the balance of the body. Second, it allows humans to maintain the head stabilized. Finally, whenever the body or head are in motion, it maintains the visual gaze on a desired target. These tasks are performed using an array of sensors that are located within the inner ear. This paper describes the design and implementation of a synthetic model of the human vestibular system. The model is based on neurophysiological evidence, which makes it necessary to model all of the neural and physical components involved in the balance of the body. The model includes a component for each of the sensors, cortical and subcortical neural structures. It also defines and generates the necessary motor output signals. The proposed model was connected to a Bioloid® Premium humanoid robot to simulate the motor output and the proprioceptive inputs. The physical tests resulted inconclusive due to the fact that the controller on the robot was incapable of handling the necessary information for the tests. However, even though the results were not the desired, the communication between the sensors and the architecture, as well as the processing inside the architecture satisfied all of the authors' expectations.

The differential effects of acute right- vs. left-sided vestibular failure on brain metabolism

The human vestibular system is represented in the brain bilaterally, but it has functional asymmetries, i.e., a dominance of ipsilateral pathways and of the right hemisphere in right-handers. To determine if acute right- or left-sided unilateral vestibular neuritis (VN) is associated with differential patterns of brain metabolism in areas representing the vestibular network and the visual-vestibular interaction, patients with acute VN (right n = 9; left n = 13) underwent resting state (18)F-FDG PET once in the acute phase and once 3 months later after central vestibular compensation. The contrast acute vs. chronic phase showed signal differences in contralateral vestibular areas and the inverse contrast in visual cortex areas, both more pronounced in VN right. In VN left additional regions were found in the cerebellar hemispheres and vermis bilaterally, accentuated in severe cases. In general, signal changes appeared more pronounced in patients with more severe vestibular deficits. Acute phase PET data of patients compared to that of age-matched healthy controls disclosed similarities to these patterns, thus permitting the interpretation that the signal changes in vestibular temporo-parietal areas reflect signal increases, and in visual areas, signal decreases. These data imply that brain activity in the acute phase of right- and left-sided VN exhibits different compensatory patterns, i.e., the dominant ascending input is shifted from the ipsilateral to the contralateral pathways, presumably due to the missing ipsilateral vestibular input. The visual-vestibular interaction patterns were preserved, but were of different prominence in each hemisphere and more pronounced in patients with right-sided failure and more severe vestibular deficits.

Modeling the Effects of Gravity Transitions in the Vestibular System: Preliminary Findings (P06.042)

Objective: To demonstrate the effects of electromagnetic induction in a model of a human vestibular system. Background Humans are exposed to different geomagnetic gradients believed to produce physiological changes in balance and locomotion. Current investigations using magnetic field-dependent chemical reactions and magnetite have not properly explained such neuro-otologic disturbances happening in and out of Earth. The electromagnetic induction mechanism model may explain the vestibular side effects affecting balance and locomotion of people exposed to different geomagnetic fields. Design/Methods: We used Matlab custom-written scripts for modeling one semicircular canal of the vestibular system, which we exposed under eight different movement conditions, ranging from common walking on earth up to spaceflights in presence of static geomagnetic fields. The electrical resistance (R) for the semicircular canal was estimated to be 6.2 x 10-4 Ω. The induced electrical voltage and current was estimated according to Faraday9s: ∇x E = -∂B / ∂t; Kirchhoff9s: C ∂V / ∂t + V/R = 0, and Ohm9s law:I = V/R. Results: The induced vestibular voltage and current obtained with this computational model was of almost four orders of magnitude. It was approximately 6000 times or 76 decibels larger for the space shuttle - where the induced vestibular current was ∼ 1 A - compared to the baseline obtained while walking. Interestingly, such induced voltage and current started to be significant, approximately 150 times or 44 decibels larger at altitudes employed by commercial airplane flights. Conclusions: We found a new geomagnetic-side effect in the human semicircular canal due to fast aerospace motion, which starts to be significant at altitudes still used for human living. Such geomagnetic effects may play a role to induce balance, gait and locomotion abnormalities in people living in extreme environments. A closed system using an internal current loop present in the inner ear, is very likely to happen in humans. Supported by: Doctor Fidias E. Leon-Sarmiento was supported the Department of Defense ( USAMRAA, W81XWH-09-1-0467 ); Doctor Carlos V. Rizzo-Sierra was supported by the University of Pamplona (Research Grant No. 0012). Disclosure: Dr. Leon-Sarmiento has nothing to disclose. Dr. Rizzo-Sierra has nothing to disclose. Dr. Gonzalez has nothing to disclose.

Vestibular perceptual thresholds to angular rotation in acute unilateral vestibular paresis and with galvanic stimulation

Studies of compensation of injury to the human vestibular system have, in the main, focused on the vestibular-ocular reflex. Probing vestibular perception allows more of the sensory pathway to be assessed. We present a novel paradigm for simultaneously testing vestibular perceptual and nystagmic thresholds to angular acceleration around an earth vertical axis. The perceptual thresholds can be modulated asymmetrically in normal subjects by DC galvanic stimulation with the head flexed in the roll plane, as expected from the main torsional plane of action of the galvanic stimulus. The perceptual and nystagmic thresholds were bilaterally elevated in acute vestibular neuritis, a unilateral condition, possibly due to central suppression of vestibular input. The degree of asymmetry in thresholds was small in comparison with the large caloric asymmetry present in the patients, indicating a relatively preserved capacity for near-threshold performance of the non-damaged labyrinth both in the "on" and "off" directions.

Sensing Movement: Microsensors for Body Motion Measurement

Recognition of body posture and motion is an important physiological function that can keep the body in balance. Man-made motion sensors have also been widely applied for a broad array of biomedical applications including diagnosis of balance disorders and evaluation of energy expenditure. This paper reviews the state-of-the-art sensing components utilized for body motion measurement. The anatomy and working principles of a natural body motion sensor, the human vestibular system, are first described. Various man-made inertial sensors are then elaborated based on their distinctive sensing mechanisms. In particular, both the conventional solid-state motion sensors and the emerging non solid-state motion sensors are depicted. With their lower cost and increased intelligence, man-made motion sensors are expected to play an increasingly important role in biomedical systems for basic research as well as clinical diagnostics.

Stability of controlled inverted pendulum under permanent horizontal perturbations of the supporting point

We consider the problem of choosing a test perturbation of a movable foundation of a single-link inverted pendulum so as to test a vestibular prosthesis prototype located at the top of this pendulum in an extreme situation. The obtained results permit concluding that the information transmitted from otolithic organs of the human vestibular system to muscles of the locomotor apparatus is very important and improves the quality of stabilization of the human vertical posture preventing the possible fall.

Motion sickness onboard ships: subjective vertical theory and its application to full-scale trials

This article presents a new approach for the prediction of motion sickness on ships, with a focus on high-speed craft. The methodology presented is based on a variant of the sensory conflict hypothesis and the human vestibular system. The proposed model was developed using control theory and is capable of taking account of all six degrees of freedom vessel motion for the prediction of motion sickness. Furthermore, full-scale trials were carried out onboard three different high-speed craft to measure the ship motions and consequently to analyse their effects on passengers in terms of motion sickness. Through the accumulated results, the developed model was validated and was compared with existing methods/criteria for the prediction of the incidence of motion sickness.

Low-frequency tuning in the human vestibular–ocular projection is determined by both peripheral and central mechanisms

We recently reported that a major contribution to the low-frequency tuning and sensitivity of the human vestibular system is the biomechanical properties of the vestibular end-organs. In the current paper, we investigate the contribution of additional mechanisms to low-frequency tuning. We compared the response properties of the vestibular system in 6 human volunteers to trains of 2ms pulses of sound and transmastoid vibration using pulse repetition frequencies of 12.5, 25, 50, 100, 200 and 400Hz. Measurements were made using two separate pathways arising from the vestibular apparatus: to the neck using vestibular evoked myogenic potentials (VEMPs), and to the eyes using ocular vestibular evoked myogenic potentials (OVEMPs). For both sound and vibration the two response pathways produced different tuning to pulse trains. The vestibulo-ocular pathway was characterised by a band-pass tuning with best frequency of 100Hz whereas the vestibulo-collic pathway showed a peak at 400Hz with sound only. These results suggest that properties of the vestibulo-ocular pathway also contribute to the low-frequency tuning that occurs for the OVEMP, in addition to previously reported end-organ effects.

A utricular origin of frequency tuning to low-frequency vibration in the human vestibular system?

Recent work has demonstrated that the human vestibular system displays a remarkable sensitivity to low-frequency vibration. To address the origin of this sensitivity we compared the frequency response properties of vestibular reflexes to 10 ms bursts of air-conducted sound and transmastoid vibration, which are thought to be differentially selective for the saccule and utricle, respectively. Measurements were made using two separate central pathways: vestibular evoked myogenic potentials (VEMPs), which are a manifestation of vestibulo-collic projections, and ocular vestibular evoked myogenic potentials (OVEMPs), which are a manifestation of vestibulo-ocular projections. For both response pathways air-conducted sound and vibration stimuli produced the same patterns of quite different tuning. Sound was characterised by a band-pass tuning with best frequency between 400 and 800 Hz whereas vibration showed a low-pass type response with a largest response at 100 Hz. Our results suggest that the tuning is at least in part due to properties of end-organs themselves, while the 100 Hz best frequency may be a specifically utricular feature.