bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic unilateral loss of otolith function revealed by the subjective visual vertical during off center yaw rotation
Authors: Böhmer Andreas , Mast Fred
Published: September 2021

Assessing the subjective visual vertical, SVV, in a static upright position is an easy clinical test in which a deviation of some 10 ∘ from true vertical indicates an acute loss of unilateral (otolithic) vestibular function on the side to which the SVV is tilted. Because this deviation of the SVV is compensated during the following months, patients with chronic unilateral vestibular loss do no longer differ from normal subjects. This study presents an experimental set-up that allows for clear detection of compensated chronic loss of unilateral otolithic function by testing the SVV. 21 normals and 17 unilaterally vestibular deafferentiated (UVD) patients (vestibular neurectomies) were first rotated on a human centrifuge about an earth vertical yaw axis through the midsagittal plane of the head ( 240 ∘ /s). This induced tilts of the gravito-inertial force (GIF) vectors, which differed at the two inner ears by 8 ∘ . During constant velocity rotation, the subjects were moved in pseudo-randomized steps laterally up to 16 cm apart from the rotation axis, inducing roll tilts of the GIF vectors up to 16 ∘ . Normal subjects set their SVV to pre-centrifugation values at positions with the midsagittal plane of their head close to the rotation axis, while chronic UVD patients indicated pre-centrifugation values during positions with the rotation axis 5.9 ± 2.5 cm paramedian on the side of the intact ear. Tilts of the GIF vectors shifted the SVV with a gain of 0.70 in normals and only 0.32 in UVD patients. Roll gains for laterally directed GIF vectors relative to the intact inner ear did not differ from medially directed roll gains in the UVD patients. The roll gains observed in this experimental set-up were lower than those observed with static body tilts or during eccentric rotation with a larger radius, which might be at least partially due to conflicting stimulation between otolithic and extra-vestibular cues.
Vestibular disorders and impaired path integration along a linear trajectory
Authors: Cohen Helen S.
Published: September 2021

The goal of this study was to determine if people use vestibular information to keep track of their positions while walking through a simple course. Subjects were normals and patients with chronic peripheral vestibulopathies – each of whom were tested once – and patients with acoustic neuromas tested pre- operatively and one and three weeks post-operatively. Subjects walked over a straight course, 7.62 m, with their eyes open and then with their eyes closed. The time needed for task performance, the forward distance subjects walked before veering, and the lateral distance subjects veered from the straight ahead were recorded. The angle of veering was then calculated. Normals were able to perform this task easily with eyes open or closed. With eyes closed pre-operative acoustic neuroma subjects walked significantly shorter distances before veering than normals but did not veer significantly more than normals or take longer than normals to perform the task. Chronic vestibulopathy subjects, by contrast, were significantly impaired compared to normals on all measures. With eyes open within a week after acoustic neuroma resection subjects could perform the task as well as normals. With eyes closed, however, post-operative subjects were impaired compared to their own pre-operative levels, but they had returned to their pre-operative levels at the second post-operative test. Ataxia was only weakly correlated to any measures and tumor size was not related to performance. These findings support the hypothesis that vestibular input is used for spatial orientation during active motion.
Short-term vestibular responses to repeated rotations
Authors: Ahn Seung Cheol , Lee Chae Yong , Kim Dong Wook , Lee Moo Hoo
Published: September 2021

To investigate the short-term vestibular habituation, we performed the 4 successive velocity step tests on 28 volunteers, the peak velocity of which was 100 deg/sec with acceleration and deceleration of 100 deg / sec 2 . As the repeated rotations might alter the vestibulo-ocular reflex (VOR), sinusoidal rotations at a frequency of 0.16 Hz were also given before and after the 4 successive velocity step tests to investigate the changes of gain and phase of VOR. The 28 volunteers were divided into two groups, group I and II, according to their responses to repeated rotations. In group I (25 subjects, mean age 23.7 year), the mean values of the slow cumulative eye position (SCEP), the time integral of eye velocity during nystagmus, was reduced after each trial of the 4-successive velocity step tests as follows; 403.4 ± 29 degree (1st trial), 346.2 ± 37 degree (2nd trial), 278.3 ± 33 degree (3rd trial) and 256.6 ± 36 degree (4th trial). The time constant of the nystagmus was also reduced as follows; 12.9 ± 0.78 second (1st trial), 12 ± 0.63 second (2nd trial), 9.7 ± 0.78 second (3rd trial) and 9.9 ± 0.54 second (4th trial). In group II (3 subjects, mean age 28.3 year), the mean values of SCEP gradually increased; 774.3 ± 135 degree (1st trial), 1127 ± 178 degree (2nd trial), 1096.3 ± 123.4 degree (3rd trial) and 1225.7 ± 199.7 degree (4th trial). The time constant of the nystagmus increased; 15.7 ± 2.7 second (1st trial), 22 ± 4.5 second (2nd trial), 22.3 ± 3.3 second (3rd trial) and 23.3 ± 5.7 second (4th trial). The gain of vestibulo-ocular reflex (VOR) induced by sinusoidal rotations at a frequency 0.16 Hz increased in both groups: 0.59 ± 0.03 to 0.78 ± 0.06 (group I) and 0.65 ± 0.07 to 1.15 ± 0.06 (group II). Phase changes were also observed. In group I, the phase was shifted from 0.6 ± 0.6 degree to − 0.40 ± 0.6 degree. In group II, the phase was shifted from 3.67 ± 1.86 degree to − 0.33 ± 0.33 degree. The repeated rotation did not induce a common nystagmic response in all subjects. Thus, person to person variations should be considered in short term vestibular habituation.
Comparison of protein kinase activity and protein phosphorylation in the medial vestibular nucleus and prepositus hypoglossi in labyrinthine-intact and labyrinthectomized guinea pigs
Authors: Kerr DeWana R. , Sansom Andrew J. , Smith Paul F. , Darlington Cynthia L.
Published: September 2021

The aim of the present study was to compare in vitro protein expression, protein kinase activity and protein phosphorylation in the medial vestibular nucleus (MVN) and prepositus hypoglossi (PH) from labyrinthine-intact guinea pigs and from guinea pigs at various stages of vestibular compensation following unilateral labyrinthectomy (UL). The ipsilateral (I-MVN) and contralateral (C-MVN) MVN, and the ipsilateral (I-PH) and contralateral (C-PH) PH, were dissected from 3 naive labyrinthine-intact guinea pigs and 55 guinea pigs at 10 hs or 53 hs following a surgical UL or sham operation. Tissue extracts were incubated with [gamma- 33 P]ATP ± Ca 2 + , phorbal 12, 13 dibutyrate and phosphatidylserine or ± Ca 2 + and calmodulin, to enhance protein kinase C (PKC) or calcium calmodulin kinase (CaMK) activity, respectively. Data were analysed as the ratio of activated to basal 33 P incorporation detected by phosphorimaging. There were similar total protein and phosphoprotein profiles in the MVN and PH, as well as both PKC and CaMKII activity, suggesting that the MVN and PH are similar in the way that proteins undergo rapid modification by phosphorylation. During the development of vestibular compensation, a 46 kDa band in C-PH displayed higher PKC-mediated phosphorylation from 10 hs post-UL compared to sham controls. Significantly greater PKC-mediated phosphorylation of proteins of approximately 18, 46 and 75 kDa was observed in C-PH at 10 hs compared to 53 hs post-UL and in most cases the phosphorylation was greater in C-PH than in the C-MVN. These results suggest that between 10 and 53 hs post-UL, PKC-mediated phosphorylation changes mainly in the C-PH rather than the ipsilateral or contralateral MVN.
William Charles Wells (1757–1817) and vestibular research before Purkinje and Flourens
Authors: Wade Nicholas J.
Published: September 2021

Vestibular research before Flourens typically involved vertigo and eye movements. In 1820 Purkinje integrated these in studies of postrotary vertigo and he is linked with Flourens as a founder of vestibular research. In the late eighteenth century Erasmus Darwin described vertigo in detail, but he did not accept that it involved an oculomotor component. Darwin reached this conclusion despite detailed experiments by William Charles Wells (1757–1817), who described the pattern of postrotary nystagmus and its dependence on head orientation during rotation. Wells generated afterimages prior to rotation and subsequently compared their motions with those of real images. He was able to distinguish between the slow and fast phases of nystagmus, its reducing amplitude following cessation of rotation, its suppression with fixation, and its torsional dimension. In many ways, Wells's experiments were more sophisticated than those of Purkinje, and he should be recognised as a founder of vestibular research. Possible reasons for the neglect of Wells's work are discussed.
Baselines for three-dimensional perception of combined linear and angular self-motion with changing rotational axis
Authors: Holly Jan E.
Published: September 2021

The laws of physics explain many human misperceptions of whole-body passive self-motion. One classic misperception occurs in a rotating chair in the dark: If the chair is decelerated to a stop after a period of counterclockwise rotation, then a subject will typically perceive clockwise rotation. The laws of physics show that, indeed, a clockwise rotation would be perceived even by a perfect processor of angular acceleration information, assuming that the processor is initialized (prior to the deceleration) with a typical subject's initial perception – of no rotation in this case. The motion perceived by a perfect acceleration processor serves as a baseline by which to judge human self-motion perception; this baseline makes a rough prediction and also forms a basis for comparison, with uniquely physiological properties of perception showing up as deviations from the baseline.

These same principles, using the motion perceived by a perfect acceleration processor as a baseline, are used in the present paper to investigate complex motions that involve simultaneous linear and angular accelerations with a changing axis of rotation. Baselines – motions that would be perceived by a perfect acceleration processor, given the same initial perception (prior to the motion of interest) as that of a typical subject – are computed for the acceleration and deceleration stages of centrifuge runs in which the human carriage tilts along with the vector resultant of the centripetal and gravity vectors. The computations generate a three-dimensional picture of the motion perceived by a perfect acceleration processor, by simultaneously using all six interacting degrees of freedom (three angular and three linear) and taking into account the non-commutativity of rotations in three dimensions.

The resulting three-dimensional baselines predict stronger perceptual effects during deceleration than during acceleration, despite the equal magnitudes (with opposite direction) of forces on the subject during acceleration and deceleration. For a centrifuge run with the subject facing tangentially in the direction of motion, the deceleration baseline shows a perception of forward tumble (pitch rotation) beginning with ascent from the earth, while the acceleration baseline does not have analogous pitch and vertical motion. These results give a three-dimensional explanation for certain puzzling acceleration-deceleration perceptual differences observed experimentally by Guedry, Rupert, McGrath, and Oman (Journal of Vestibular Research, 1992 (2).). The present analysis is consistent with, and expands upon, previous analyses of individual components of motion.
Is “ambient vision” distributed in the brain?
Authors: Previc Fred H. , Beer Jeremy , Liotti Mario , Blakemore Colin , Fox Peter
Published: September 2021

Ambient vision comprises the visual functions that are associated with the maintenance of spatial orientation and that depend on peripheral, preconscious visual inputs. Although a limited number of brain areas appear to be activated by coherent wide-field-of-view (WFOV) motion in more than one axis, a diffuse pattern of lateralized brain activity occurs in response to clockwise or counterclockwise ambient visual roll motion [15]. In the present study involving positron emission tomography (PET), a similar finding was shown for rightward versus leftward yaw stimulation. A total of 18 PET scans were obtained from six subjects in response to either leftward or rightward WFOV motion in a collimated display subtending [Formula: see text] horizontally. Rightward stimulation elicited mainly activation throughout the right hemisphere, whereas leftward stimulation elicited mainly activation throughout the left hemisphere. These findings provide further evidence that the ambient vision signal is either processed or transmitted throughout the entire brain, as befits a visual function that is fundamental to all other perceptual systems.
The human linear vestibulo-ocular reflex to transient accelerations: Visual modulation of suppression and enhancement
Authors: Gianna Claire C. , Gresty Michael A. , Bronstein Adolfo M.
Published: September 2021

Visual modulation of the linear vestibulo-ocular reflex (LVOR) was investigated in 4 normal subjects exposed to translational interaural transient accelerations of 0.08 g and 0.17 g. Binocular eye movements were recorded with the scleral search-coil technique. LVOR modulation with target proximity was studied using earth-fixed targets at distances of 30 and 60 cm (LVOR-E). LVOR suppression (LVOR-S) was provoked by similar targets which were head-fixed. For both conditions, linear acceleration evoked compensatory slow-phases whose velocities were, from onset, enhanced in proportion to acceleration and target proximity. At 80 ms after motion onset, i.e. before visually-guided eye movements could aid target fixation, gains (eye velocity/ relative target velocity) during LVOR-E averaged 0.32 (S.D. 0.07) over all combinations of accelerations and target distances. At this time, eye velocities for LVOR-S were on average 33% for LVOR-E ([Formula: see text]/s vs. [Formula: see text]/s). During LVOR-S, a marked suppression of eye movements appeared at 102 ms (S.D. 10 ms). We conclude that mechanisms other than pursuit can be used to attenuate the LVOR at [Formula: see text] ms but their effect is weak. The marked suppression observed around 100 ms might be due to an early visual effect on vestibular pathways or by some independent voluntary control mechanism.
Vertical nystagmus in normal subjects: Effects of head position, nicotine and scopolamine
Authors: Kim J.I. , Somers J.T. , Stahl J.S. , Bhidayasiri R. , Leigh R.J.
Published: September 2021

We measured gaze stability in darkness of four normal humans using the search coil technique. Subjects were tested first with their heads erect, and then with their heads positioned 180 degrees upside-down. In each position, subjects held their head stationary for one minute, and then actively performed pitch rotations for 20 sec. All subjects showed sustained chin-beating nystagmus in the upside-down position. Each subject showed a significant increase of slow-phase velocity directed towards their brow after 40 sec in the inverted versus erect position. Pitch head rotation had little effect on subsequent nystagmus, except for transient reversal in one subject. The sustained changes of vertical eye drifts induced by 180 deg change of head position suggest that otolithic factors may contribute to vertical nystagmus in normals. The subjects were retested after wearing a nicotine patch for 2 hours. In three subjects, nicotine induced brow-beating nystagmus; adopting a head-hanging position increased this nystagmus in two subjects. In a third session, subjects were tested after wearing a scopolamine patch for 2 hours; results were generally similar to the control condition. We conclude that normal subjects may show chin-beating (“downbeating”) nystagmus in a head-hanging position in darkness, reflecting a normal, physiological change in otolithic inputs brought about by the head orientation.
Age-related change of the neuronal number in the human medial vestibular nucleus: A stereological investigation
Authors: Tang Yong , Lopez Ivan , Baloh Robert W.
Published: September 2021

An unbiased stereological method was used to assess the effect of aging on the number of neurons in the human medial vestibular nucleus. We studied 13 normal brainstem specimens (age at death from 40 to 93 years) that were part of a prior study that counted neuronal profiles and used a correction factor to estimate the number of neurons in the human vestibular nucleus. On average, we found [Formula: see text] ([Formula: see text]) neurons in the medial vestibular nucleus, which is 18% significant decrease in the number of neurons with aging. This age-related neuronal loss in the vestibular nucleus could have important functional implications regarding the well-known deterioration in balance that occurs with aging.
Effects of lifetime ethanol consumption on postural control: A computerized dynamic posturography study
Authors: Ahmad Saad , Rohrbaugh John W. , Anokhin Andrey P. , Sirevaag Erik J. , Goebel Joel A.
Published: September 2021

The relationship between lifetime alcohol consumption and postural control was investigated in 35 subjects with no clinically-detectable neurologic abnormalities, using computerized dynamic posturography (CDP) procedures. The estimated total number of lifetime alcoholic drinks was positively correlated with anteroposterior sway spectral power within the 2–4 Hz and 4–6 Hz frequency bands, in three Sensory Organization Test (SOT) conditions: eyes closed with stable support surface (SOT 2), eyes open with sway-referenced support (SOT 4), and eyes closed with sway-referenced support (SOT 5). All correlations remained significant after controlling for subject age, and were increased after excluding nine drug-abusing subjects. In contrast to the strong findings for frequency-based measures, no correlation was observed using conventional amplitude-based sway measures. These results suggest that 1) alcohol consumption compromises postural control in an exposure-dependent manner, and 2) sway frequency analysis reveals pathological processes not manifested in conventional CDP measures of sway amplitude.
Vestibular adaptation studied with a prosthetic semicircular canal
Authors: Lewis Richard F. , Gong Wangsong , Ramsey Mitchell , Minor Lloyd , Boyle Richard , Merfeld Daniel M.
Published: September 2021

We have developed and tested a prosthetic semicircular canal that senses angular head velocity and uses this information to modulate the rate of current pulses applied to the vestibular nerve via a stimulating electrode. In one squirrel monkey, the lateral canals were plugged bilaterally and the prosthesis was secured to the animal's head with the angular velocity sensor parallel to the axis of the lateral canals. In the first experiment, the stimulating electrode was placed near the ampullary nerve of one lateral canal. Over a period of two weeks, the gain of the horizontal VOR during yaw axis rotation gradually increased, although the response magnitude remained relatively small. In the second experiment, the stimulating electrode was placed near the ampullary nerve of the posterior canal, but the orientation of the velocity sensor remained parallel to the axis of the lateral canals. Over a one-week period, the axis of the VOR response gradually shifted towards alignment with the (yaw) axis of head rotation. Chronic patterned stimulation of the eighth nerve can therefore provide adequate information to the brain to generate a measurable VOR response, and this can occur even if the prosthetic yaw rotation cue is provided via a branch of the VIIIth nerve that doesn't normally carry yaw rotational cues. The results provided by this pilot study suggest that it may be feasible to study central adaptation by chronically modifying the afferent vestibular cue with a prosthetic semicircular canal.
Bilateral peripheral vestibular lesions produce long-term changes in spatial learning in the rat
Authors: Russell Noah A. , Horii Arata , Smith Paul F. , Darlington Cynthia L. , Bilkey David K.
Published: September 2021

In order to investigate whether bilateral peripheral vestibular lesions cause long-term impairment of spatial learning, rats were tested in a reference memory radial arm maze learning task at least 5 weeks following a bilateral labyrinthectomy (BL) or sham control lesion. All control rats reached criterion (i.e., 1 error or less, averaged across 7 trials for 3 consecutive days of training) but only 4 of the 8 BL rats had reached criterion by day 21 of the training sessions. The control rats reached criterion more quickly than the lesioned rats (Control, 7.0 ± 0.63 days, Lesioned, 15.8 ± 1.4 days, [Formula: see text], p < 0.0001). This difference resulted from the greater number of errors made by the BL animals. However, the latency to respond was comparable as a result of the increased locomotor activity of the BL group (i.e., ’hyperkinesis), and the overall rate of acquisition of the task, as indicated by analysis of the exponential decrease in errors over the entire training period, was not significantly different between the 2 groups. The results of this study demonstrate that BL in rats produces long-term changes in performance in a spatial reference memory task, which are not simply due to the inability to move but may relate to the way that the brain uses vestibular information to create spatial representations and determines behavioural strategies on the basis of these representations.
A comparison of the monothermal and bithermal caloric tests
Authors: Enticott J.C. , Dowell R.C. , O'Leary S.J.
Published: September 2021

This study considered whether the monothermal (MT) caloric test could predict the normality of the full conventional bithermal (BT) caloric test, and therefore be an alternative to full caloric investigation. This would have the advantages of reducing test time and patient discomfort as only two caloric tests would be needed instead of four. 744 BT caloric investigations were examined, and the unilateral weakness and directional preponderance calculated for the BT and the MT stimuli. By defining the BT results as the standard, the false-positive and false-negative results of the MT test were derived. Overall using very strict MT difference criteria of less than 5% and no spontaneous nystagmus, false-negative rates for the cool MT were very low (< 1%) and better than the warm MT (< 7.1%) suggesting that the cool MT was a reliable screen test. However, unacceptably high false-positive rates were produced reflecting more than 3/4 of normal BT results failing the MT criterion. This unacceptable false-positive rate decided against implementing the MT test at our facility. The results of this study however have guided the use of the cool air-stimulus first during BT testing and, when completion of the BT is not possible or inadvisable, satisfying the stringent MT criterion confidently indicates with a probability of > 99% the absence of an abnormal BT result.
Otolith-ocular responses in patients with surgically confirmed unilateral peripheral vestibular loss
Authors: Furman Joseph M. , Hsu Li-Chi , Whitney Susan L. , Redfern Mark S.
Published: September 2021

The chronic effects of unilateral peripheral vestibular loss (UPVL) are influenced by vestibular compensation. This study documents the balance-related symptoms and quantitative vestibular laboratory testing of 20 patients with surgically confirmed UPVL. Included are measures of the semicircular canal-ocular reflex, the otolith-ocular reflex, and both static and dynamic semicircular canal-otolith-interaction. This study differs from previous studies of patients with UPVL in that a large number of patients with surgically confirmed lesions were tested with three types of off-vertical axis rotation, several of the patients had anatomically preserved superior vestibular nerves, and self-perceived level of disability related to dizziness and imbalance were available. Results confirmed previously reported changes in the vestibulo-ocular reflex of patients with UPVL. Also, there was no apparent effect of anatomically preserving the superior vestibular nerve during surgical resection of vestibular schwannomas based on either subjective or objective measures of vestibular dysfunction. Further, there were no apparent correlations between subjective measures of dizziness and imbalance and objective measures of vestibulo-ocular function. These results have clinical implications for the management of patients with unilateral vestibular loss and provide insights into the process of vestibular compensation especially with respect to the otolith-ocular reflex.
Hydrostatic pressure effects on vestibular hair cell afferents in fish and crustacea
Authors: Fraser Peter J. , Cruickshank Stuart F. , Shelmerdine Richard L.
Published: September 2021

Following the discovery of a hydrostatic pressure sensor with no associated gas phase in the crab, and the knowledge that several systems of cells in culture show long term alterations to small changes in hydrostatic pressure, we show here that vestibular type II hair cells in a well known model system (the isolated elasmobranch labyrinth), are sensitive to hydrostatic pressure. This new finding for the vertebrate vestibular system may provide an explanation for low levels of resting activity in vertebrate hair cells and explain how fish without swim bladders sense hydrostatic cues. It could have implications for humans using their balancing systems in hypobaric or hyperbaric environments such as in aircraft or during space exploration. Although lacking the piston mechanism thought to operate in crab thread hairs which sense angular acceleration and hydrostatic pressure, the vertebrate system may use larger numbers of sensory cells with resultant improvement in signal to noise ratio. The main properties of the crab hydrostatic pressure sensing system are briefly reviewed and new experimental work on the isolated elasmobranch labyrinth is presented.
Vestibular suppression during space flight
Authors: Watt Douglas , Lefebvre Luc
Published: September 2021

Normal movements performed while voluntarily fixing the head to the torso can lead to motion sickness in susceptible individuals. The underlying mechanism may involve excessive suppression of vestibular responses. A similar motor strategy is often adopted in the early days of a space flight and might contribute to the development of space motion sickness. In a recent experiment, we monitored the eye, head and upper torso rotations of four Life and Microgravity Spacelab crew members. For the purposes of this study, all data were excluded except for periods during which the subject was performing pure yaw-axis head movements. All subjects showed a significant increase in gaze slip on the first day of their mission, suggesting that increased vestibular suppression was occurring. Furthermore, this amount of increased suppression would have been more than adequate to produce motion sickness in susceptible individuals on the ground. The results support the theory of two, independent mechanisms for space motion sickness.
Postural instability in Meniere's disease
Authors: Havia M. , Kentala E. , Pyykkö I.
Published: September 2021

In order to characterize the postural instability by duration of Meniere's disease (MD) we present the results of 180 MD patients tested on posturography. The duration of the disease varied from 4 weeks to 36 years. The patients were clinically examined and they had filled a questionnaire concerning their symptoms. Postural instability was examined by a force platform posturography and the results are expressed as sway velocities (SV). There was no statistically significant difference in the mean SV between groups of different duration of MD. The number of the patients with normal eyes open SV declined by duration of the illness from 73% to 38% but the decline was not statistically significant. The mean age in the different duration groups of MD varied from 47 to 61 years. In general 58% of the patients had their eyes open SV in normal range and 55% when measured eyes closed. When examining the SV between the 4 different hearing stages of MD we found that those belonging into the group III (pure tone average [PTA] 41–70 dB) had significantly higher eyes open and eyes closed SV's than the patients in the group I (PTA under 25 dB).
The role of vection, eye movements and postural instability in the etiology of motion sickness
Authors: Flanagan Moira B. , May James G. , Dobie Thomas G.
Published: September 2021

Motion sickness is a term that is commonly used to describe the ill effects of many provocative motion (e.g. seagoing or air travel) and apparent motion (e.g. IMAX movies and virtual reality) environments on human well-being and performance. It can be extremely debilitating and yet we do not have a precise understanding of its cause. This study evaluates the importance of three factors that are purported to be involved in the etiology of motion sickness (MS). Most provocative motion environments cause three distinct, but possibly related, responses: reflexive eye movements (EM), sensory conflict (SC), and postural instability (PS). Three current theories, concerning the etiology of motion sickness, emphasize one of these responses, but deny the importance of the others. Such theoretical approaches preclude the possibility of a synergistic interaction of these factors. This experiment employed a three-factor experimental design wherein each factor was manipulated alone or in combination with the others. The independent variables involved two levels of: PS (induced by having the subject stand on a stationary platform or on a posturally challenging platform mounted atop a partially inflated rubber inner tube); SC (with or without illusory self movement elicited visually by whole field stimulation); and EM (unrestricted or controlled by a stable fixation point). Analysis of measures of PS, SC and EM confirmed the effectiveness of these manipulations. Analysis of MS measures (questionnaires, magnitude ratings, tolerance times) revealed a main effect of SC (p < 0.01), increased MS found with illusory self motion conditions. In addition, measures of MS symptomatology revealed a significant three-way interaction between SC, PS and EM (p < 0.05), greater amounts of MS found with conditions of illusory self motion, postural challenge, and unrestricted EM. This suggests support for a multi-factorial approach to the study of MS etiology. These findings suggest a major role of SC in the elicitation of MS, but also suggest important contributions from the EM and PS mechanisms.
Preservation of tap vestibular evoked myogenic potentials despite resection of the inferior vestibular nerve
Authors: Brantberg Krister , Mathiesen Tiit
Published: September 2021

Sound and skull-tap induced vestibular evoked myogenic potentials (VEMP) were studied in a 43-year-old man following inferior vestibular neurectomy. Surgery was performed because of a small acoustic neuroma. Postoperative caloric testing suggested sparing of superior vestibular nerve function on the operated side. In response to sound stimulation there were no VEMP on the operated side, irrespective of whether sounds were presented by air- or bone-conduction. This suggests sound-induced VEMP to be critically dependent on inferior vestibular nerve function and this is in agreement with present knowledge. However, VEMP were obtained in response to forehead skull taps, i.e. positive-negative VEMP not only on the healthy side but also on the operated side. This suggests remnant vestibular function on the operated side of importance for forehead skull tap VEMP, because with complete unilateral vestibular loss there are no (positive-negative) VEMP on the lesioned side. Thus, forehead skull-tap VEMP depend, at least partly, on the superior vestibular nerve function.
Torsional vestibulo-ocular reflex during whole-body oscillation in the upright and the supine position: II. Responses in patients after vestibular neuritis
Authors: Schmid-Priscoveanu A. , Kori A.A. , Straumann D.
Published: September 2021

In a recent study we demonstrated that otolith input modifies the torsional angular vestibulo-ocular reflex (torVOR) of healthy human subjects: Compared to turntable oscillations in supine position, oscillations in upright position increased the gain of torVOR by 0.1 and cancelled the phase lead originating from low-frequency semicircular canal signals. We asked whether these otolith-related changes of torVOR are still present in patients after vestibular neuritis (VN). Eight patients were sinusoidally oscillated about their naso-occipital axis in supine (canal-only stimulation) and upright (canal-and-otolith stimulation) position. Three-dimensional eye movements were recorded with dual search coils. The patients showed similar otolith-related gain and phase changes of the torVOR as healthy subjects: the gain increased by about 0.1 (p < 0.05) and the low-frequency phase lead from semicircular canal signals was abolished. These results indicate that otolith function after VN is still sufficient to interact with semicircular canal signals to optimize torsional gaze stabilization when the head is upright.
System identification of the human vestibulo-ocular reflex during head-free tracking
Authors: Tangorra James L. , Jones Lynette A. , Hunter Ian W.
Published: September 2021

A method was developed to identify the linear, system level dynamics of the horizontal, angular vestibulo-ocular reflex (VOR) as it stabilized vision during head-free tracking of a visual target. Small amplitude, broad spectrum, stochastic torque perturbations were applied to the head while the subject tracked an unpredictable, moving target with active head and eye motions. Stochastic system identification techniques were used to design the torque and target inputs and to conduct the analysis such that the linear dynamics of the VOR, independently of the visual system's influence on eye motions, were determined. The linear analysis was limited to evaluating VOR dynamics from approximately 0.5 to 4.5 Hz. Nonlinearities in the head-neck system affected the low frequency response of the head to the torque perturbations, and the eye velocity sequence was affected by nonlinearities and degraded by noise at high frequencies. The VOR's gain was near 1.0 between about 0.5 and 2.5 Hz, and then decreased steadily to 0.85 as the frequency increased towards 4.0 Hz. The VOR phase angle was also frequency dependent and corresponded to VOR eye motions lagging the head's disturbance motion by less than 10 ms at frequencies greater than 1.0 Hz.
Improved postural control through repetition and consolidation
Authors: Tjernström F. , Fransson P.-A. , Magnusson M.
Published: September 2021

Research regarding the optimal frequency of training in postural control rehabilitation has been sparse. Posturography with vibratory proprioceptive stimulation was performed with eyes open and closed on 36 healthy subjects divided into 3 groups. Each group was tested 5 times, though with different time-intervals; 20 minutes, 3 hours and 24 hours respectively. Two different adaptive processes seems to be involved in the formation of a new movement pattern when exposed to a postural disturbance, one fast adaptation active during each test occasion and a second adaptation active between the consecutive tests. As the same adaptation pattern was found regardless the repetition time interval, the results imply either that the consolidation process of the new motor memory is time-independent or that the stimulus was sufficiently strong to induce fast consolidation thus leaving the time-interval unimportant. The findings suggest that it is primarily the number of repetitions in the exercises that governs the outcome of training, whereas the time interval between the exercises is of less importance.
Instantaneous rotation axes during active head movements
Authors: Moore Steven T. , Hirasaki Eishi , Raphan Theodore , Cohen Bernard
Published: September 2021

Rotation axes were calculated during active head movements using a motion analysis system. The mean rotation axis for 1 Hz head pitch when seated was posterior (6 mm) and inferior (21 mm) to the interaural axis, shifting 16 mm downwards when standing. During seated 2 Hz head pitch the rotation axis was close to the interaural axis, shifting downwards 15 mm when standing. This downward shift suggests that cervical vertebrae were recruited during head pitch with the trunk unsupported. The proximity of the pitch axis to the otoliths implies minimal otolith activation during small-amplitude, high-frequency pitch rotations, such as those encountered during locomotion. The mean rotation axis for 1 Hz yaw rotation was located slightly posterior (10 mm) to the interaural axis at the midpoint between the vestibular labyrinths when both seated and standing. In addition, the orientation of the plane of yaw rotation relative to the stereotaxic horizontal plane (pitched 5° nose-down) was essentially fixed in head coordinates, regardless of the pitch orientation of the head, suggesting that yaw movements occur about an axis restricted by the mechanical structure of the atlanto-axial joint. The results demonstrate that the instantaneous rotation axes technique overcomes the inherent instability of the helical-axis representation for small head movements.
Fluid-structural dynamics of ground-based and microgravity caloric tests
Authors: Kassemi M. , Oas J.G. , Deserranno Dimitri
Published: September 2021

Microgravity caloric tests aboard the 1983 SpaceLab1 mission produced nystagmus results with an intensity comparable to those elicited during post- and pre- flight tests, thus contradicting the basic premise of Barany's convection hypothesis for caloric stimulation. In this work, we present a dynamic fluid structural analysis of the caloric stimulation of the lateral semicircular canal based on two simultaneous driving forces for the endolymphatic flow: natural convection driven by the temperature-dependent density variation in the bulk fluid and expansive convection caused by direct volumetric displacement of the endolymph during the thermal irrigation. Direct numerical simulations indicate that on earth, the natural convection mechanism is dominant. But in the microgravity environment of orbiting spacecraft, where buoyancy effects are mitigated, expansive convection becomes the sole mechanism for producing cupular displacement. A series of transient 1 g and microgravity case studies are presented to delineate the differences between the dynamics of the 1 g and microgravity endolymphatic flows. The impact of these different flow dynamics on the endolymph-cupula fluid-structural interactions is also analyzed based on the time evolutions of cupular displacement and velocity and the transcupular pressure differences.
The balance control of bilateral peripheral vestibular loss subjects and its improvement with auditory prosthetic feedback
Authors: Hegeman J. , Honegger F. , Kupper M. , Allum J.H.J.
Published: September 2021

Objective: We investigated whether long-term bilateral vestibular loss subjects could combine auditory biofeedback of trunk sway with their remaining natural sensory inputs on balance to provide an improved control of trunk sway. A successful integration of natural and artificial signals would provide a basis for a balance prosthesis. Methods: Trunk sway of 6 bilateral peripheral vestibular loss subjects (BVL) was recorded using either angular position- or velocity-based auditory feedback or no feedback during stance and gait tasks. Roll and pitch trunk movements were recorded with angular velocity transducers mounted just above the waist and feedback without a delay to 4 loudspeakers placed at the left, right, front and rear borders of the 5 m long by 4 m wide test environment. The two types of auditory feedback or no feedback were provided to the subjects in random order. In the feedback modes, sway greater than a preset angle (ca. 0.5 deg) or velocity (ca. 3 deg/s) thresholds caused a tone to be emitted from the speaker towards which the subject moved. The tone volume increased with increasing angle or angular velocity amplitude. Results: For all stance tasks BVL subjects without auditory feedback had a significantly different balance control with respect to that of normal controls. BVL sway values eyes open on a normal surface were reduced with auditory feedback with the greatest reductions in the roll plane. Specifically for the task of standing on 1 leg eyes open with position-auditory- feedback, amplitudes of pitch and roll angles and angular velocities were indistinguishable from those of normal controls. Sway during stance tasks on foam with eyes closed showed no improvement with feedback, remaining greater than normal. For some gait tasks there was a decrease in trunk sway with velocity feedback. Conclusions: These initial results indicate that subjects with vestibular loss could incorporate the auditory prosthetic sensory information into their balance commands, particularly in the roll plane if the balance task is performed with eyes open. Position information appears more useful than velocity information in reducing trunk sway during stance tasks. Future work will need to determine the effect of a training time on the improvement in balance control using such a prosthetic device and the ideal position and velocity auditory feedback combination.
A rodent model for artificial gravity: VOR adaptation and Fos expression
Authors: Kaufman Galen , Weng Tianxiang , Ruttley Tara
Published: September 2021

Vestibulo-ocular reflex (VOR) adaptation and brainstem Fos expression as a result of short radius cross-coupling stimuli were investigated to find neural correlates of the inherent Coriolis force asymmetry from an artificial gravity (AG) environment. Head-fixed gerbils (Meriones unguiculatus, N = 79) were exposed, in the dark, to 60–90 minutes of cross-coupled rotations, combinations of pitch (or roll) and yaw rotation, while binocular horizontal, vertical, and torsional eye position were determined using infrared video-oculography. Centripetal acceleration in combination with angular cross-coupling was also studied. Simultaneous sinusoidal rotations in two planes (yaw with roll or pitch) provided a net symmetrical stimulus for the right and left labyrinths. In contrast, a constant velocity yaw rotation during sinusoidal roll or pitch provided the asymmetric stimulus model for AG. We found orthogonally oriented half-cycle VOR gain changes. The results depended on the direction of horizontal rotation during asymmetrical cross-coupling, and other aspects of the stimulus, including the phase relationship between the two rotational inputs, the symmetry of the stimulus, and training. Fos expression also revealed laterality differences in the prepositus and inferior olivary C subnucleus. In contrast the inferior olivary beta and ventrolateral outgrowth were labeled bilaterally. Additional cross-coupling dependent labeling was found in the flocculus, hippocampus, and several cortical regions, including the perirhinal and temporal association cortices. Analyses showed significant differences across the brain regions for several factors (symmetry, rotation velocity and direction, the presence of centripetal acceleration or a visual surround, and training). Finally, animals compensating from a unilateral surgical labyrinthectomy who received multiple cross-coupling training sessions had improved half-cycle VOR gain in the ipsilateral eye with head rotation toward the intact side. We hypothesize that cross-coupling vestibular training can benefit aspects of motor recovery or performance.
Human ocular torsion and perceived roll responses to linear acceleration
Authors: Zupan Lionel H. , Merfeld Daniel M.
Published: September 2021

We investigated if human ocular torsion (OT) and perceived roll (PR) are elicited in response to either dynamic interaural linear acceleration or dynamic roll tilt of the gravito-inertial force (GIF). We expanded a previous study [26] that measured only OT across a limited frequency-range (from 0.35 Hz to 1 Hz) by simultaneously measuring OT and PR at three very low (0.01, 0.02 and 0.05 Hz) and one high (1 Hz) frequencies. Three experimental conditions were investigated: (1) Y-Upright with acceleration along the interaural (Y) axis while upright, (2) Y-Supine with acceleration along the Y-axis while supine, and (3) Z-RED with acceleration along the rostro-caudal (Z) axis with right-ear-down (RED). OT was measured by video-oculography, while PR was measured by use of a somatosensory bar. OT and PR were qualitatively different. Large OT responses were measured for Y-Upright and Y-Supine, while large perceived roll responses were observed for Y-Upright and Z-RED. OT for Z-RED was small, and PR for Y-Supine was absent. In conclusion, OT and PR appear governed by qualitatively different neural mechanisms. OT appears mostly influenced by central low-pass filtering of interaural graviceptor cues, while PR appears mostly influenced by roll tilt of the GIF.
Lateral rectus muscle changes after bilateral neonatal labyrinthectomy in the ferret
Authors: Shall Mary S. , Van Cleave Susan , Dimitrova Diana M. , Goldberg Stephen J.
Published: September 2021

The vestibular system is essential to the coordination of eye movements during head movements. Exercise, such as the eye movements mediated by the vestibular system, is a major factor in the development of muscle fiber types and the strength of muscle. In this study, the contents of the inner ear were removed (labyrinthectomy) from (LAB) ferrets at postnatal day 10 (P10) and raised with control (SHAM) animals. At P30, the lateral rectus muscles (LR) were removed to analyze the expression of myosin heavy chain (MHC) isoforms and to measure the least diameter of the developmental, slow and fast type muscle fibers. Another set of animals were sacrificed at P120 to analyze MHC isoform expression and muscle fiber diameters, as well as the contractile characteristics of the LR were measured prior to sacrifice. The average LAB LR was significantly stronger than the SHAM LR and the muscle fibers of the LAB animals were larger in diameter. The LAB animals expressed more type IIx and less slow type MHC. These results support the hypothesis that input from the inner ear influence the development of strength and muscle diameter in the ferret extraocular muscles.
Neonatal bilabyrinthectomy leads to changes in skeletal muscle fiber form and function
Authors: Shall Mary S. , Lanzino Desiree J. , Van Cleave Susan , Goldberg Stephen J.
Published: September 2021

Children with hypoactive semicircular canals commonly have delayed motor development. We studied ferrets whose vestibular labyrinths were removed at postnatal day 10 (P10) to evaluate 1) development of motor behavior, 2) soleus contractile characteristics, 3) muscle fiber diameter, and 4) the expression of myosin heavy chain (MHC) isoforms. At P30 labyrinthectomized (LAB) ferrets exhibited a significant delay in motor development. At P120, the LAB ferrets continued to have significantly more difficulty with dynamic balance than the SHAM ferrets. At P30, the muscle fibers were about the same diameter as those in the sham operated ferrets (SHAM) at the same age but significantly more developmental MHC isoforms were expressed in the LAB soleus muscle. At P120, both the LAB soleus and medial gastrocnemius expressed significantly more type IIX MHC. The P120 LAB soleus muscle was significantly weaker and the muscle fibers were significantly smaller. These results support the hypothesis that vestibular receptors are important to the development of upright posture and balance activities, and influence muscle fiber development and MHC expression in postural muscles.