bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of two head autorotation tests
Authors: Hirvonen Timo P , Aalto Heikki , Pyykkö Ilmari , Juhola Martti
Published: September 2021

The head autorotation test is a novel method for studying the high-frequency vestibuloocular reflex without heavy machinery to generate whole-body rotation. Despite many studies with the test, the method is far from standardized, and no comparison has been made of different versions of the test. The objective of this study was to compare the vestibuloocular reflex of 100 healthy subjects measured simultaneously with two versions of the head autorotation test. Gain, phase, asymmetry, and the frequency bands reached were determined in the frequency bands of 1, 2, 3, 4, and 5 Hz. The gain measured with both tests was close to unity (range 0.95–1.04) from 1 to 4 Hz and about 0.9 at 5 Hz. In the test developed by Vorteq the phase lagged ( − 7 to − 21 ∘ ) in all the frequency bands, and it differed significantly from the phase lead of 2 to 5 ∘ that was measured by the other test. The asymmetry measured with the Vorteq test increased continuously from 1.5% variation, which was larger in the higher frequency bands. In conclusion, the high-frequency vestibuloocular reflex of healthy subjects can be quantified with active head oscillation. Both tests produced similar gain results, but the phase results differed systematically. Thus, the results of different head autorotation tests may not be directly comparable.
Recovery of vestibulo-ocular reflex-function in subjects with an acute unilateral peripheral vestibular deficit
Authors: Allum J.H.J. , Ledin T.
Published: September 2021

The centrally controlled compensation for a reduced horizontal vestibulo-ocular reflex (VOR) gain caused by a unilateral afferent deficit is usually studied following a selective surgical procedure which completely lesions the vestibular nerve or blocks the horizontal semicircular canal. The more common, unilateral, vestibular deficit encountered clinically, is a partial loss of peripheral vestibular function, following which peripheral recovery and/or central compensation may occur. We investigated changes of the VOR gain in response to a sudden, idiopathic, unilateral vestibular deficit in 64 subjects by examining the responses to low-frequency, whole-body, rotations about an earth vertical axis with different accelerations (5, 20 and 40 deg / sec 2 ) during in- and out-patient visits separated by 4 months in an attempt to identify changes brought about by peripheral recovery and by central compensation processes. Peripheral function was assumed to be measured by the response to caloric irrigation. It improved some 30% between the two visits. VOR responses for rotations towards the deficit side also improved between the two visits. Most improvement occurred for 20 deg / sec 2 accelerations. However, the correlation coefficient between rotation and caloric responses was always less than 0.6. Unlike caloric responses which improved over time, responses for rotations to the intact side did not change between the visits. For this reason, the majority of observed VOR rotation responses were nearly symmetrical at the time of the second visit, despite being below normal levels. These findings suggest that both peripheral recovery and central compensation processes help restore symmetrical VOR function for head rotations after a partial unilateral vestibular deficit. However the improvement of VOR response symmetry, particularly to slow ( < 40 deg / sec 2 ) accelerations, is largely independent of the recovery of peripheral sensitivity.
Spatial orientation of the angular vestibulo-ocular reflex
Authors: Cohen Bernard , Wearne Susan , Dai Mingjia , Raphan Theodore
Published: September 2021

During vestibular nystagmus, optokinetic nystagmus (OKN), and optokinetic afternystagmus (OKAN), the axis of eye rotation tends to align with the vector sum of linear accelerations acting on the head. This includes gravitational acceleration and the linear accelerations generated by translation and centrifugation. We define the summed vector of gravitational and linear accelerations as gravito-inertial acceleration (GIA) and designate the phenomenon of alignment as spatial orientation of the angular vestibuloocular reflex (aVOR). On the basis of studies in the monkey, we postulated that the spatial orientation of the aVOR is dependent on the slow (velocity storage) component of the aVOR, not on the short latency, compensatory aVOR component, which is in head-fixed coordinates. Experiments in which velocity storage was abolished by midline medullary section support this postulate. The velocity storage component of the aVOR is likely to be generated in the vestibular nuclei, and its spatial orientation was shown to be controlled through the nodulus and uvula of the vestibulo-cerebellum. Separate regions of the nodulus/uvula appear to affect the horizontal and vertical/torsional components of the response differently. Velocity storage is weaker in humans than in monkeys, but responds in a similar fashion in both species. We postulate that spatial orientation of the aVOR plays an important role in aligning gaze with the GIA and in maintaining balance during angular locomotion.
Head impulses reveal loss of individual semicircular canal function
Authors: Aw S.T. , Halmagyi G.M. , Black R.A. , Curthoys I.S. , Yavor R.A. , Todd M.J.
Published: September 2021

We studied individual semicircular canal responses in three dimensions to high-acceleration head rotations (“head impulses”) in subjects with known surgical lesions of the semicircular canals, and compared their results to those of normal subjects. We found that vestibular-ocular reflex (VOR) gains at close to peak head velocity in response to yaw, pitch and roll impulses were reliable indicators of semicircular canal function. When compared to normals, lateral canal function showed a 70–80% gain at peak of yaw head velocity during ipsilesional yaw impulses. After the loss of one vertical canal function there was a 30–50% and torsional VOR gain in response to ipsilesional pitch and roll impulses respectively. Bilateral deficits in anterior or posterior canal function resulted in a 80–90% impulses, while the loss of ipsilateral anterior and posterior canal functions will result in a 80–90% ipsilesional roll impulses. Three-dimensional vector analysis and animation of the VOR responses in a unilateral vestibular deafferented subject to yaw, pitch and roll impulses further demonstrated the deficits in magnitude and direction of the VOR responses following the loss of unilateral lateral, anterior and posterior canal functions.
An overview of the clinical use of dynamic posturography in the differential diagnosis of balance disorders
Authors: Allum John H.J. , Shepard Neil T.
Published: September 2021

Dynamic posturography comprises a series of balance control tests which help physicians overcome numerous diagnostic and treatment challenges arising when examining patients complaining of a debilitating balance disorder. These challenges include the specific differential diagnosis, documentation of symptoms and assessment of functional disability. It must be determined whether the cause of the disability is an organic sensory deficit, a central nervous system (CNS) lesion or a non-organic (that is, possibly psychogenic or just overtly simulated) disorder. This review is targeted towards providing the reader (a) an overview of the effects sensori-motor deficits have on balance control, specifically vestibulo-spinal and proprioceptive reflex deficits; and, (b) how these effects may be assessed objectively in a clinical setting to differentiate between various organic and non-organic balance-disorders. The techniques used to study these effects are based on the analysis of both rapid balance-correcting and slow balance-stabilizing responses to fast and slow movements in the pitch plane of the support surface on which the test subject stands.
The activities-specific balance confidence scale and the dizziness handicap inventory: a comparison
Authors: Whitney S.L. , Hudak M.T. , Marchetti G.F.
Published: September 2021

Vestibular dysfunction can have a tremendous impact on an individual’s quality of life. The purpose of this paper is to determine if the level of handicap reported by individuals on the Dizziness Handicap Inventory (DHI), an inventory developed for use with individuals with complaints of dizziness symptoms, will be consistent with that reported on the Activities-specific Balance Confidence Scale (ABC), a tool developed for use with elderly individuals that attempts to assess a person’s confidence level in performing activities of daily living (ADL’s). A sample of convenience was used consisting of 71 subjects (15 males and 56 females) from a local Balance and Vestibular Clinic. The subjects ranged in age from 26 to 88 years of age. Both the DHI and the ABC were administered as part of an initial physical therapy evaluation to new patients at the clinic. A moderately strong negative correlation was found between the scores of the two inventories ( r s = − 0.6350). The results suggest that the ABC is a valid tool for use with individuals with complaints of dizziness.
Voluntary movement strategies of individuals with unilateral peripheral vestibular hypofunction*
Authors: Borello-France Diane F. , Gallagher Jere D. , Redfern Mark , Furman Joseph M. , Carvell George E.
Published: September 2021

This study compared voluntary movement strategies of patients with unilateral peripheral vestibular hypofunction with those of age-matched healthy control subjects. All subjects performed three voluntary movement tasks with their dominant upper extremity: a forward flexion arm movement through 90 degrees, a reach to an overhead target, and a reach to a side target. Subjects performed the movement tasks sitting and standing (Body Position), and under precued and choice reaction time (RT) conditions (Task Certainty). Measures of motor planning and movement execution included RT and movement time (MT), respectively. Statistical analysis included separate Group x Task Certainty x Body Position ANOVA calculations for each task. Across tasks, results suggested no between group differences for RT. A Task Certainty main effect for the side and overhead tasks indicated that the choice RT situation resulted in longer RTs as compared to the precued RT condition. Movement time differed between the two groups. Across all three voluntary movement tasks, vestibular impaired subjects moved more slowly than control subjects. Providing vestibular subjects with a precue did not bring MT performance to the level of controls. Body position influenced MT for the side task only. Across both groups of subjects, MT for the side task was longer when performed in the standing position. The results of this study suggest that individuals with unilateral peripheral vestibular hypofunction initiate voluntary movement responses with similar timing as control subjects, but require more time to complete the movement. Vestibular rehabilitation should include goal-directed movement and should address issues of movement speed.
Circular vection in patients with age-related macular degeneration
Authors: Fushiki Hiroaki , Takata Satoru , Nagaki Yasunori , Watanabe Yukio
Published: September 2021

We have used optokinetic stimulation in patients with unilateral age-related macular degeneration (AMD) and central scotoma to investigate the possible contribution of the central visual field to circular vection (CV). Six patients aged 42–73 years with unilateral AMD and an aged-matched control group of nine elderly adults aged 47–75 years were examined. Monocular visual field defects were verified with the Goldmann perimeter by kinetic perimetry. The device used to induce CV was a random dot pattern projected onto a hemispherical dome with a radius of 75 cm. The pattern was rotated horizontally at a constant acceleration of 1 deg/s 2 . Monocular stimuli were randomly repeated two to three times in both temporal-nasal (T-N) and nasal-temporal (N-T) directions. The latency of onset of CV was measured for each stimulus presentation. In the age-matched control group the CV latencies varied from 4.2 to 72.0 s. In each case, however, the CV latencies were stable. No significant differences in CV latencies were found between right and left eyes in both stimulus directions ( p > 0.05). In patients with AMD, no statistically significant difference in CV latency was found between the affected and unaffected eyes ( p > 0.05). Marked central visual field loss in AMD does not significantly impair peripherally induced CV. Our results are compatible with the hypothesis that the peripheral retina dominates CV.
Click evoked EMG responses in sternocleidomastoid muscles: characteristics in normal subjects
Authors: Li M.W. , Houlden D. , Tomlinson R.D.
Published: September 2021

Recordings were obtained from a total of 25 normal subjects of the electromyographic (EMG) responses in the sternocleidomastoid muscle (SCM) to intense sound stimuli. While previous authors have demonstrated these responses exist, it has remained unclear whether the EMG response is unilateral or bilateral in nature. Accordingly, we chose a remote site, linked-wrists, for our reference electrodes so that we could be certain that no significant volume conduction of potentials could occur from the source in the SCM to the reference site. When this was done we found that if the sternum was used as a reference site, as was the case in previous studies, some subjects exhibited bilateral responses while in others, the response was ipsilateral. However, with linked-wrists as the reference site, responses were always purely ipsilateral. Furthermore, recordings that used the sternum or the ipsilateral mastoid process as active sites and linked-wrists as a reference, exhibited responses which were inverted. Thus, both the sternum and the ipsilateral mastoid process are electrically active due to volume conduction from the nearby source in the SCM. The ambiguity in previous recordings can be attributed to the use of these active sites as a reference. When SCM responses are recorded versus a remote, electrically inactive site, the responses are purely ipsilateral.
Semicircular canal and saccular influence on the subjective visual horizontal during gondola centrifugation
Authors: Tribukait A.
Published: September 2021

Measurements of the subjective visual horizontal (SVH) were performed in 11 healthy test persons during an increase of the resultant gravitoinertial force vector in a large swing-out gondola centrifuge. Three levels of hypergravity (1.5g, 2.0g, 2.5g) were used, each with a duration of 4 minutes and with 1–2 minute pauses at 1.0g in between. The direction of the resultant gravitoinertial force vector was always parallel with the head and body length axis. Hence, there was no roll stimulus to the otolith organs. The swing-out of the gondola during acceleration, however, is sensed by the vertical semicircular canals as a change in roll head position, thus creating an otolith-semicircular canal conflict. After acceleration of the centrifuge there was a tilt of the SVH relative to the resultant gravitoinertial horizontal. This tilt gradually decayed during the 4-minute period of recordings. For a subgroup of seven test subjects who had completely normal ENG-recordings in 1g environment, the initial offset of SVH and the time constants for exponential decay were determined for each g level; initial offsets: 9 . 9 ∘ (1.5g), 7 . 7 ∘ (2.0g), 6 . 1 ∘ (2.5g); time constants: 89s (1.5g), 74s (2.0g), 37s (2.5g). The offset of SVH is interpreted as being the result of mainly the stimulus to the vertical semicircular canals during acceleration of the centrifuge. The slow decay, however, does not correspond to the dynamics of the semicircular canal system, and is suggested to reflect some kind of central position storage mechanism. A smaller offset and more rapid decay for the higher g loads may be explained by an increasing dominance of graviceptive input, presumably from the saccules. In conclusion, these results might suggest the role of the vertical semicircular canals as well as the sacculus in the formation of SVH. They may also have relevance with regard to the spatial disorientation problem in aviators.
Eye movements during torso rotations in labyrinthine-defective subjects
Authors: Ivanenko Y.P. , Viaud-Delmon I. , Sémont A. , Gurfinkel V.S. , Berthoz A.
Published: September 2021

The aim of this study was to examine whether the chronic loss of vestibular function modifies perceptual and oculomotor responses during torso rotations in darkness. Subjects (4 patients with complete vestibular loss and 7 healthy volunteers) were seated on a rotating chair. Stimuli consisted of sinusoidal chair rotations ( ± 30 ∘ , 0.1 Hz and 0.011 Hz). We used 2 conditions: space stationary head (neck stimulation) and space stationary head and shoulders (torso stimulation). Horizontal eye deviations and slow component of eye movements were analysed. The results showed that eye movements and perception of head motion in space during neck stimulation were similar to those during torso stimulation both in normal and labyrinthine-defective (LD) subjects. During low-frequency chair rotations (0.011 Hz) all subjects perceived illusory head or head and shoulder rotation in space (as if the lower part of the body was stationary relative to the room) and shifted their gaze in the direction of illusory head rotation. In these conditions there was no significant difference in eye movements between normal and LD subjects. During higher frequency chair rotations (0.1 Hz), LD subjects had significantly larger eye deviations as well as increases in the gain of the slow component of eye movements relative to normals. In these conditions patients mostly perceived illusory head or head and shoulder rotation in space while normal subjects mainly perceived the head as stationary in space. The results indicate that 1) neck and torso rotations can evoke similar ocular responses in LD subjects, 2) the chronic loss of vestibular function modifies the representation of axial body segment motion relative to space.
EquiTest modification with shank and hip angle measurements: differences with age among normal subjects
Authors: Speers Rosemary A. , Shepard Neil T. , Kuo Arthur D.
Published: September 2021

The Sensory Organization Test protocol of the EquiTest system (NeuroCom International, Clackamas Oregon) tests utilization of visual, vestibular, and proprioceptive sensors by manipulating the accuracy of visual and/or somatosensory inputs during quiet stance. In the standard Sensory Organization Test, both manipulation of sensory input (sway-referencing) and assessment of postural sway are based on ground reaction forces measured from a forceplate. The purpose of our investigation was to examine the use of kinematic measurements to provide a more direct feedback signal for sway-referencing and for assessment of sway. We compared three methods of sway-referencing: the standard EquiTest method based on ground reaction torque, kinematic feedback based on servo-controlling to shank motion, and a more complex kinematic feedback based on servo-controlling to follow position of the center of mass (COM) as calculated from a two-link biomechanical model. Fifty-one normal subjects (ages 20–79) performed the randomized protocol. When using either shank or COM angle for sway-referencing feedback as compared to the standard EquiTest protocol, the Equilibrium Quotient and Strategy Score assessments were decreased for all age groups in the platform sway-referenced conditions (SOT 4, 5, 6). For all groups of subjects, there were significant differences in one or more of the kinematic sway measures of shank, hip, or COM angle when using either of the alternative sway-referencing parameters as compared to the standard EquiTest protocol. The increased sensitivities arising from use of kinematics had the effect of amplifying differences with age. For sway-referencing, the direct kinematic feedback may enhance ability to reduce proprioceptive information by servo-controlling more closely to actual ankle motion. For assessment, kinematics measurements can potentially increase sensitivity for detection of balance disorders, because it may be possible to discriminate between body sway and acceleration and to determine the phase relationship between ankle and hip motion.
Are vestibular hair cells excited to death by aminoglycoside antibiotics?
Authors: Smith Paul F.
Published: September 2021

Aminoglycoside antibiotics are commonly prescribed throughout the world for the treatment of serious gram-negative bacterial infections. However, their use is limited by nephrotoxicity and ototoxicity. Although the traditional explanation for their ototoxicity in cochlear and vestibular hair cells has been the inhibition of mitochondrial protein synthesis, evidence is accumulating to suggest that many aminoglycosides cause excitotoxicity in hair cells as a result of their agonist action at the polyamine site on the N- methyl-D-aspartate (NMDA) receptor. The aim of this minireview is to summarise and critically evaluate this evidence and to consider the therapeutic implications of this hypothesis
Effects of adaptation of vestibulo-ocular reflex function on manual target localization
Authors: Bloomberg Jacob J. , Merkle Lauren A. , Barry Susan R. , Huebner William P. , Cohen Helen S. , Mueller S. Alyssa , Fordice James
Published: September 2021

The goal of the present study was to determine if adaptive modulation of vestibulo-ocular reflex (VOR) function is associated with commensurate alterations in manual target localization. To measure the effects of adapted VOR on manual responses we developed the Vestibular-Contingent Pointing Test (VCP). In the VCP test, subjects pointed to a remembered target following passive whole body rotation in the dark. In the first experiment, subjects performed VCP before and after wearing 0.5X minifying lenses that adaptively attenuate horizontal VOR gain. Results showed that adaptive reduction in horizontal VOR gain was accompanied by a commensurate change in VCP performance. In the second experiment, bilaterally labyrinthine deficient (LD) subjects were tested to confirm that vestibular cues were central to the spatial coding of both eye and hand movements during VCP. LD subjects performed significantly worse than normal subjects. These results demonstrate that adaptive change in VOR can lead to alterations in manual target localization.
The effects of scopolamine and cyclizine on visual-vestibular interaction in humans
Authors: Gowans Jennifer , Matheson Anna , Darlington Cynthia L. , Smith Paul F.
Published: September 2021

The aim of the present study was to investigate the effects of scopolamine (1.5 mg, transdermal patch) and cyclizine (50 mg tablet), at the doses usually used for the relief of motion sickness, on postural sway, optokinetic nystagmus (OKN) and circularvection (CV) in humans, using a within-subjects, double-blind, placebo-controlled design. Scopolamine and cyclizine were found to have no significant suppressive effect on these aspects of visual-vestibular interaction. Postural sway and CV were not significantly affected by either drug treatment; OKN SPV was significantly increased ( p < 0.05), although OKN amplitude and frequency were unaffected. These results suggest that scopolamine and cyclizine, at doses used for the relief of motion sickness, may have minimal suppressive effects on these aspects of visual-vestibular interaction.
Influence of fixation on circular vection
Authors: Fushiki Hiroaki , Takata Satoru , Watanabe Yukio
Published: September 2021

The contribution of fixation to latency of circular vection (CV) was examined in twenty-five normal adults aged 18–30 years. For induction of self-motion a random dot pattern was projected onto a hemispherical dome. The pattern was rotated either about the subject’s vertical axis or about their interaural axis at a constant acceleration of 1 deg / s 2 . For the group tested, the perceived CV latencies were significantly shorter with fixation than without fixation in both horizontal and vertical CV. The effect of fixation was pronounced in subjects with longer latencies. The mean CV latencies for two different fixation points between the subject’s eyes and the moving pattern did not differ significantly. Our results suggest that the potential influence of fixation must be carefully controlled in studies of visually induced self-motion. Possible explanations for the effect of fixation on the generation of CV will also be discussed.
Adaptation of the phase of the human linear vestibulo-ocular reflex (LVOR) and effects on the oculomotor neural integrator
Authors: Hegemann Stefan , Shelhamer Mark , Kramer Phillip D. , Zee David S.
Published: September 2021

The phase of the translational linear VOR (LVOR) can be adaptively modified by exposure to a visual-vestibular mismatch. We extend here our earlier work on LVOR phase adaptation, and discuss the role of the oculomotor neural integrator. Ten subjects were oscillated laterally at 0.5 Hz, 0.3 g peak acceleration, while sitting upright on a linear sled. LVOR was assessed before and after adaptation with subjects tracking the remembered location of a target at 1 m in the dark. Phase and gain were measured by fitting sine waves to the desaccaded eye movements, and comparing sled and eye position. To adapt LVOR phase, the subject viewed a computer-generated stereoscopic visual display, at a virtual distance of 1 m, that moved so as to require either a phase lead or a phase lag of 53 deg. Adaptation lasted 20 min, during which subjects were oscillated at 0.5 Hz/0.3 g. Four of five subjects produced an adaptive change in the lag condition (range 4–45 deg), and each of five produced a change in the lead condition (range 19–56 deg), as requested. Changes in drift on eccentric gaze suggest that the oculomotor velocity-to-position integrator may be involved in the phase changes.
Modal analysis of the diaphragm of the semicircular canal
Authors: Njeugna E. , Kopp C.M. , Eichhorn J.-L.
Published: September 2021

The aim of this paper is to determine the domain of validity of calculated quasi-static deformations of the cupula and of ciliar deflections on the crista ampullaris. Several three-dimensional models of the isolated ampullar diaphragm of the human semicircular canal and of that of the frog are studied theoretically by modal analysis. The four first modes of vibration are determined for each structure. Numerical simulations prove that for the first mode of vibration, the cupular deformation has the same shape as that obtained by applying a static pressure difference across the ampullar diaphragm. We studied also the effect of the mechanical properties (Young's modulus and Poisson's coefficient) of the components of the ampullar diaphragm on the vibration modes and their frequencies. The condition, which must be satisfied by the cupular internal viscosity, to have resonance near the natural frequency of the ampullar diaphragm is determined.
The menstrual cycle and susceptibility to coriolis-induced sickness
Authors: Cheung Bob , Heskin Raquel , Hofer Kevin , Gagnon Martin
Published: September 2021

Survey studies on motion sickness susceptibility suggest that females tend to report greater severity in illness and higher incidence of vomiting than males. Menstruation is said to be a contributing factor. A recent study suggested that females were least susceptible to seasickness during ovulation in a “round the world” yacht race. Sixteen subjects (18–36 years old) were exposed to Coriolis cross-coupling stimulation in the laboratory. They were tested once during permenstruation (Day 1–5), ovulation (Day 12–15) and premenstruation (Day 24–28), based on a normalized 28-day cycle, in a randomised design. Physiological measurements of motion sickness included forearm and calf cutaneous blood flow. Subjective evaluation of sickness symptoms was based on Graybiel's diagnostic criteria and Golding's rating method. Our results indicated that under controlled laboratory conditions, different phases of the menstrual cycle appear to have no influence on subjective symptoms of motion sickness or on cutaneous blood flow increase in the forearm and calf. The lack of commonality between the types and levels of hormones that are released during motion sickness and those that are involved in different menstrual phases appears to support our findings.
The directions of nystagmus and apparent self-motion evoked by caloric tests and angular accelerations
Authors: Kolev Ognyan I.
Published: September 2021

Purpose:

To further investigate the direction of (I) nystagmus and (II) self-motion perception induced by two stimuli: (a) caloric vestibular stimulations and (b) a sudden halt during vertical axis rotation.

Subjects and methods:

Twelve normal humans received caloric stimulation at 44°C, 30°C, and 20°C while in a supine position with the head inclined 30° upwards. In a second test they were rotated around the vertical axis with the head randomly placed in two positions: tilted 30° forward or tilted 60° backward, at a constant velocity of 90°/sec for 2 minutes and then suddenly stopped. After both tests they were asked to describe their sensations of self-motion. Eye movements were recorded with an infrared video-technique.

Results:

Caloric stimulation evoked only horizontal nystagmus in all subjects and induced a non-uniform complex perception of angular in frontal and transverse planes (the former dominated) and linear movements along the antero-posterior axis (sinking dominated) of the subject's coordinates. The self-motion was felt with the whole body or with a part of the body. Generally the perception evoked by cold (30°C) and warm (44°C) calorics was similar, although there were some differences. The stronger stimulus (20°C) evoked not only quantitative but also qualitative differences in perception. The abrupt halt of rotation induced self-motion perception and nystagmus only in the plane of rotation. The self-motion was felt with the whole body.

Conclusion:

There was no difference in the nystagmus evoked by caloric stimulation and a sudden halt of vertical axis rotation (in head positions to stimulate the horizontal canals); however, the two stimuli evoked different perceptions of self-motion. Calorics provoked the sensation of self-rotation in the frontal plane and linear motion, which did not correspond to the direction of nystagmus, as well as arcing and a reset phenomenon during angular and linear self-motion, caloric-induced self-motion can be felt predominantly or only with a part of the body, depending on the self-motion intensity. The findings indicate that, unlike the self-motion induced by sudden halt of vertical axis rotation, several mechanisms take part in generating caloric-induced self-motion.
The effects of stochastic monopolar galvanic vestibular stimulation on human postural sway
Authors: Scinicariello Anthony P. , Inglis J. Timothy , Collins J.J.
Published: September 2021

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.
Over-stimulation of the vestibular system and body balance
Authors: Charles Corinne , Cian Corinne , Nougier Vincent , Bigard Xavier A. , Job Agnès , Raphel Christian
Published: September 2021

The purpose of this study was to examine whether an over-stimulation of the vestibular system, induced by thousands of time saccadic head stimulations, affects the vestibular sensitivity, and consequently if such a phenomenon could contribute to the deterioration of postural stability observed after a long distance running exercise. Eighteen athletic subjects performed a 20.5 km over ground race with an average speed of 15 km.h − 1 , corresponding roughly to 7,500 strides shocks with associated saccadic accelerations transmitted to the head. A preliminary validation of the exercise protocol was realized to confirm the effect of the sustained exercise on body balance by recording standard postural parameters. A visually perceived eye level (VPEL) task was used to indirectly assess otolithic sensitivity motionless or undergoing low centrifugation conditions, before and after exercise. Results obtained from body balance analysis confirmed a decreased postural stability illustrated by increased postural oscillations after the 20.5 km run. Under low centrifugation conditions, results showed a lowering of the VPEL with the increase of the gravito-inertial acceleration in accordance with the literature. However, no significant change in the VPEL after a sustained running exercise was observed. In conclusion, the vestibular sensitivity at the otolithic level does not seem to be altered by an intensive running exercise and then failed to play a key role in the post-exercise deterioration of postural stability.
On the origin of susceptibility to kinetotic swimming behaviour in fish: A parabolic aircraft flight study
Authors: Hilbig Reinhard , Anken Ralf H. , Rahmann Hinrich
Published: September 2021

Humans taking part in parabolic aircraft flights (PAFs) may suffer from motion sickness (SMS, a kinetosis; it comprises a dynamic and a static component). It has been argued that the so-called static variety of SMS during PAFs might be based on asymmetric statoliths (i.e., differently weighed statoliths on the right and the left side of the head), with asymmetric inputs to the brain being disclosed in microgravity. Since it has been repeatedly shown earlier that some fish of a given batch reveal a kinetotic behaviour during PAFs (especially so-called spinning movements and looping responses), we investigated whether fish swimming kinetotically in microgravity have a pronounced inner ear otolith asymmetry. Therefore, the swimming behaviour of larval cichlid fish was video-recorded during PAFs and subsequently, size and asymmetry (size difference between the left and the right side) of inner ear otoliths were determined. The asymmetry of utricular otoliths of kinetotic samples was found to be significantly higher than that of normally behaving experimental specimens. Regarding the asymmetry of saccular otoliths of the two groups, statistically different results were not obtained. The findings strongly support the earlier theoretical concept, according to which otolith asymmetry causes (static) SMS.
Context-specific adaptation of saccade gain in parabolic flight
Authors: Shelhamer Mark , Clendaniel Richard A. , Roberts Dale C.
Published: September 2021

Previous studies established that vestibular reflexes can have two adapted states (e.g., gains) simultaneously, and that a context cue (e.g., vertical eye position) can switch between the two states. Our earlier work demonstrated this phenomenon of context-specific adaptation for saccadic eye movements: we asked for gain decrease in one context state and gain increase in another context state, and then determined if a change in the context state would invoke switching between the adapted states. Horizontal and vertical eye position and head orientation could serve, to varying degrees, as cues for switching between two different saccade gains. In the present study, we asked whether gravity magnitude could serve as a context cue: saccade adaptation was performed during parabolic flight, which provides alternating levels of gravitoinertial force (0 g and 1.8 g). Results were less robust than those from ground experiments, but established that different saccade magnitudes could be associated with different gravity levels.
Quantitative measurement of vertigo frequency: Preliminary results
Authors: Zalewski-Zaragoza Robert Aureo , Viirre Erik Scott
Published: September 2021

Persons who experience vertigo often describe their symptoms as a sensation of oscillations. Based on such a description, a pilot study was performed to determine if the frequency of the vertigo sensation could be quantified in a manner analogous to tone matching in tinnitus treatment. Fifteen subjects were tested using a virtual image system that consisted of a head mounted display showing a scene that oscillated horizontally or vertically at an adjustable frequency. Subjects were asked to adjust the direction and frequency to match their typical vertigo sensation. Results show that most persons with chronic vertigo had symptoms that could be realistically simulated by vection induced by the oscillating scene and that matched to a consistent specific frequency. They reported an average frequency of 1.09 Hz (range 0.27 to 3.3 Hz, SD 0.25). The large majority (13 out of 15) matched to a horizontal stimulus. Subjects that gave particularly high subjective ratings of the similarity of the motion sensation (7–8 out of 10) from the vection to their vertigo had lower frequency matches (average 0.61 +/- 0.25). Repeated measurements in 4 subjects 8 to 27 days later showed consistent results. This vertigo measurement technique may be used in the future to assess the ability of vestibular rehabilitation to reduce chronic vertigo. Identification of a specific frequency of chronic vertigo may be important in the specification of rehabilitation exercises.
Neurovestibular symptoms following space flight
Authors: Bacal Kira , Billica Roger , Bishop Sheryl
Published: September 2021

Neurovestibular symptoms experienced by astronauts in the post-flight period were examined using data from medical debriefs contained in the NASA Longitudinal Study of Astronaut Health database. Ten symptoms were identified (clumsiness, difficulty concentrating, persisting sensation aftereffects, nausea, vomiting, vertigo while walking, vertigo while standing, difficulty walking a straight line, blurred vision, and dry heaves), of which eight were crossed with twelve demographic parameters (mission duration, astronaut gender, age, one-g piloting experience, previous space flight experience, g-suit inflation, g-suit deflation, in-flight space motion sickness, in-flight exercise, post-flight exercise, mission role, fluid loading). Three symptoms were experienced by a majority of subjects, and another two by more than a quarter of the subjects. Intensity of the symptoms was mild, suggesting that they are unlikely to pose a risk to the crew during landing and the post-flight period. Seven of the symptoms and eight of the parameters under study were found to be significantly associated with each other.
A review of the effects of space flight on the asymmetry of vertical optokinetic and vestibulo-ocular reflexes
Authors: Clément Gilles
Published: September 2021

Prolonged microgravity during orbital flight is a unique way to modify the otolith inputs and to determine the extent of their contribution to the vertical vestibulo-ocular reflex (VOR) and optokinetic nystagmus (OKN). This paper reviews the data collected on 10 astronauts during several space missions and focuses on the changes in the up-down asymmetry. Both the OKN elicited by vertical visual stimulation and the active VOR elicited by voluntary pitch head movements showed an asymmetry before flight, with upward slow phase velocity higher than downward slow phase velocity. Early in-flight, this asymmetry was inverted, and a symmetry of both responses was later observed. An upward shift in the vertical mean eye position in both OKN and VOR suggests that these effects may be related to otolith-dependent changes in eye position which, in themselves, affect slow phase eye velocity.
Perceptual stability during active head movements orthogonal and parallel to gravity
Authors: Jaekl P. , Jenkin M. , Harris L.R.
Published: September 2021

We measured how much the visual world could be moved during various head rotations and translations and still be perceived as visually stable. Using this as a monitor of how well subjects know about their own movement, we compared performance in different directions relative to gravity. For head rotations, we compared the range of visual motion judged compatible with a stable environment while rotating around an axis orthogonal to gravity (where rotation created a rotating gravity vector across the otolith macula), with judgements made when rotation was around an earth-vertical axis. For translations, we compared the corresponding range of visual motion when translation was parallel to gravity (when imposed accelerations added to or subtracted from gravity), with translations orthogonal to gravity. Ten subjects wore a head-mounted display and made active head movements at 0.5 Hz that were monitored by a low-latency mechanical tracker. Subjects adjusted the ratio between head and image motion until the display appeared perceptually stable. For neither rotation nor translation were there any differences in judgements of perceptual stability that depended on the direction of the movement with respect to the direction of gravity.
Rotation otolith tilt-translation reinterpretation (ROTTR) hypothesis: A new hypothesis to explain neurovestibular spaceflight adaptation
Authors: Merfeld Daniel M.
Published: September 2021

Normally, the nervous system must process ambiguous graviceptor (e.g., otolith) cues to estimate tilt and translation. The neural processes that help perform these estimation processes must adapt upon exposure to weightlessness and readapt upon return to Earth. In this paper we present a review of evidence supporting a new hypothesis that explains some aspects of these adaptive processes. This hypothesis, which we label the rotation otolith tilt-translation reinterpretation (ROTTR) hypothesis, suggests that the neural processes resulting in spaceflight adaptation include deterioration in the ability of the nervous system to use rotational cues to help accurately estimate the relative orientation of gravity ("tilt"). Changes in the ability to estimate gravity then also influence the ability of the nervous system to estimate linear acceleration ("translation"). We explicitly hypothesize that such changes in the ability to estimate "tilt" and "translation" will be measurable upon return to Earth and will, at least partially, explain the disorientation experienced when astronauts return to Earth. In this paper, we present the details and implications of ROTTR, review data related to ROTTR, and discuss the relationship of ROTTR to the influential otolith tilt-translation reinterpretation (OTTR) hypothesis as well as discuss the distinct differences between ROTTR and OTTR.
Interaction of vestibular, echolocation, and visual modalities guiding flight by the big brown bat, Eptesicus fuscus
Authors: Horowitz Seth S. , Cheney Cheryl A. , Simmons James A.
Published: September 2021

The big brown bat (Eptesicus fuscus) is an aerial-feeding insectivorous species that relies on echolocation to avoid obstacles and to detect flying insects. Spatial perception in the dark using echolocation challenges the vestibular system to function without substantial visual input for orientation. IR thermal video recordings show the complexity of bat flights in the field and suggest a highly dynamic role for the vestibular system in orientation and flight control. To examine this role, we carried out laboratory studies of flight behavior under illuminated and dark conditions in both static and rotating obstacle tests while administering heavy water ( D 2 O) to impair vestibular inputs. Eptesicus carried out complex maneuvers through both fixed arrays of wires and a rotating obstacle array using both vision and echolocation, or when guided by echolocation alone. When treated with D 2 O in combination with lack of visual cues, bats showed considerable decrements in performance. These data indicate that big brown bats use both vision and echolocation to provide spatial registration for head position information generated by the vestibular system.
Prevalence of dizziness and vertigo in an urban elderly population
Authors: Jönsson Radi , Sixt Eva , Landahl Sten , Rosenhall Ulf
Published: September 2021

The prevalence of balance symptoms (vertigo, dizziness, and dysequilibrium) was investigated in an epidemiological study of elderly people, the longitudinal and cross-sectional gerontological and geriatric population study from Göteborg, Sweden (H70). Three different age cohorts were studied, one at age 70, one at age 75 and one at ages 79, 82, 85, 88 and 90 years. Altogether 2011 participants answered the questionnaire at 3197 occasions. The overall prevalence of balance problems at age 70 was 36% (women) and 29% (men). Balance symptoms were more common among women than men, and increased with increasing age. At ages 88–90 years the corresponding values were 51–45%.. The most common symptom was poor balance/general unsteadiness (11–41%). Rotatory symptoms occurred in 2–17%. Other types of symptoms were less common. Precipitating factors were rising from supine to sitting position in 17–40%. Balance symptoms in a side position were uncommon, but occurred more often when tilting the head backwards (up to 14%). Signs that possibly could indicate neurological involvement were uncommon. Falls in conjuncture to dizziness, vertigo and similar symptoms occurred in 7–15%, in about equal proportions indoors as outdoors.
Labyrinthectomy decreases bone mineral density in the femoral metaphysis in rats
Authors: Levasseur Régis , Sabatier Jean Pierre , Etard Olivier , Denise Pierre , Reber Annie
Published: September 2021

To determine whether the vestibular system could influence bone remodeling in rats, we measured bone mineral density with dual energy X-rays absorptiometry before and 30 days after bilateral labyrinthectomy. Comparatively to intact control rats, labyrinthectomized animals showed a reduced bone mineral density in distal femoral metaphysis (p = 0.007): the variations between D0 and D30 were +3.0% for controls and -13.9% for labyrinthectomized rats. No significant difference between the 2 groups was observed in the whole body mineral density. These results suggest that the peripheral vestibular apparatus is a modulator of bone mass and more specifically in weight bearing bone. We discuss possible mechanisms of this vestibular influence probably mediated by the sympathetic nervous system.