bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of inducible nitric oxide synthase (iNOS/NOS II) in the hydropic vestibule after injection of keyhole limpet hemocyanin into the endolymphatic sac of guinea pigs
Authors: Watanabe Ken-ichi , Tomiyama Shunichi , Jinnouchi Ken , Hess Alexander , Michel Olaf , Yagi Toshiaki
Published: September 2021

This study was undertaken to examine the expression of inducible nitric oxide synthase (iNOS / NOS II) in the hydropic vestibule of guinea pigs.

Animals were systemically sensitized with 500 μg of keyhole limpet hemocyanin. Two weeks after the first injection, keyhole limpet hemocyanin (100 μg/5 μl) was injected into the endolymphatic sac following the intradural approach, and the next day temporal bones were removed for the immunohistochemical examination.

Endolymphatic hydrops was evidenced by the expansion of the Reissner's membrane in the cochlea after direct injection of keyhole limpet hemocyanin into the endolymphatic sac. Inducible nitric oxide synthase expression was increased in the sensory cells, supporting cells and vestibular ganglion cells, while temporal bones, where only phosphate buffered saline was injected, did not show any inducible nitric oxide synthase immunoreactivity.

High levels of inducible nitric oxide synthase-catalyzed nitric oxide were detected prior to the development of the inner ear dysfunction. Our results suggest that the occurrence of inducible nitric oxide synthase immunoreactivity parallels the inner ear disturbance as seen in endolymphatic hydrops.
Head stability in older adults during walking with and without visual input
Authors: Cromwell Ronita L. , Newton Roberta A. , Forrest Gail
Published: September 2021

The purposes of this study were to 1) characterize head stabilization in older adults across the frequency spectrum of walking, and 2) assess the ability of older adults to adapt head-trunk coordination to maintain head stability in the absence of vision. Sagittal plane head and trunk angular velocities in space were measured for 17 healthy older adults while walking with eyes open (EO) and eyes closed (EC). Average walking velocity and cadence were also determined. Frequency analyses were used to examine head velocities in space and head-on-trunk with respect to trunk gain and phase values across the frequency spectrum of walking. Average walking velocity decreased with EC. Head stability was maintained during EO, but decreased during EC as indicated by increased head velocities across the frequency spectrum. Gain values increased while phase values remained similar during EC walking demonstrating diminished coordination of head-trunk movements. When relying on vestibular and proprioceptive information, older adults were unable to adapt head-trunk movements suggesting impaired plasticity of these systems with age.
Visual-vestibular interaction during OVAR in the elderly
Authors: Furman Joseph M. , Redfern Mark S.
Published: September 2021

This study assessed visual-otolith interaction in healthy older humans and compared responses from older subjects to those of younger subjects. Using off-vertical axis rotation (OVAR) to stimulate the otolith organs, eye movement responses, measured using electro-oculography, were recorded during rotation in the dark, rotation with an earth-fixed lighted visual surround, and rotation with a subject-fixed fixation target. Results indicated that older subjects, like young subjects, exhibit a modulation component that was as large during rotation with a lighted earth-fixed visual surround as that seen in the dark and a modulation component during rotation with a subject-fixed visual target that was incompletely suppressed. The modulation component was, in general, larger in the older subjects. This study confirms findings from a previous study of visual-otolith interaction in young subjects and suggests that older subjects, like young subjects, have difficulty visually suppressing the modulation component induced by off-vertical axis rotation.
Vestibular loss disrupts control of head and trunk on a sinusoidally moving platform
Authors: Buchanan John J. , Horak Fay B.
Published: September 2021

Twelve subjects, 6 bilateral vestibular-loss (3 well compensated and 3 poorly compensated) and 6 controls, attempted to maintain balance during anterior-posterior sinusoidal surface translation at 6 different frequencies. For frequencies ≤ 0.25 Hz well compensated and control subjects rode the platform by fixing the head and upper-trunk with respect to the support surface, and for frequencies ≥ 0.75 Hz, these subjects fixed their head/upper-trunk in space. Poorly compensated vestibular subjects showed large head and center of mass variability and were unable to balance at frequencies requiring a head fixed in space pattern. All vestibular subjects were less stable with vision than the controls. Without vision, vestibular subjects experienced more falls than the controls at all frequencies, with falls observed in 61% trials and 16% information is important in stabilizing head and upper-trunk motion in space. Visual and somatosensory information can compensate, in part, for vestibular-loss. The results are discussed in light of models that characterize postural control in a vestibular/visual top-down and somatosensory bottom-up manner.
Multivariate vestibular testing: Laterality of unilateral Ménière's disease
Authors: Dimitri P.S. , Wall C. , Rauch S.D.
Published: September 2021

This paper discusses the use of vestibular testing to discriminate between right (n = 29) and left (n = 27) Ménière's disease. We examined reduced vestibular response (RVR), directional preponderance, and spontaneous and positional nystagmus measurements from electronystagmography, as well as the asymmetry measurements from the sinusoidal harmonic acceleration test, to determine whether multivariate logistic regression could improve upon the discrimination performance of RVR alone. We found that patients with a spontaneous or positional nystagmus often had a “recovery nystagmus”, beating in the opposite direction of that predicted for an acute lesion. When present, the direction and magnitude of such nystagmus could be used in the classification algorithm to increase the discriminatory power over RVR alone, but in these patients the rotation test asymmetry measurements were rendered useless. In the absence of spontaneous or positional nystagmus, asymmetry measurements significantly enhanced right/left discrimination. Directional preponderance was insignificant in determining the side of lesion.
Vestibular evoked myogenic potentials in response to laterally directed skull taps
Authors: Brantberg Krister , Tribukait Arne
Published: September 2021

In recent years it has been demonstrated that loud clicks generate short latency vestibular evoked myogenic potentials (VEMP). It has also been demonstrated that midline forehead skull tap stimulation evokes similar VEMP. In the present study, the influence of skull tap direction on VEMP was studied in 13 normal subjects and in five patients with unilateral vestibular loss. Gentle skull taps were delivered manually above each ear on the side of the skull. The muscular responses were recorded over both sternocleidomastoid muscles using skin electrodes. Among the normals, laterally directed skull taps evoked “coordinated contraction-relaxation responses”, i.e. skull taps on one side evoked a negative-positive “inverted” VEMP on that side and a positive-negative "normal" VEMP on the other side. Among patients with unilateral vestibular function loss, skull taps above the lesioned ear evoked similar coordinated contraction-relaxation responses. However, skull taps above the healthy ear did not evoke that type of response. These findings suggest that laterally directed skull taps activate mainly the contralateral labyrinth.
Development of a biophysical model for vestibular prosthesis research
Authors: Rubinstein J.T. , Santina C.C. Della
Published: September 2021

Physiologic properties of primary vestibular neurons are compared and contrasted with properties of primary auditory neurons. The differences and similarities suggest possible coding strategies for a vestibular implant. The degree of spike rate variability, or coefficient of variation (CV), is a prominent physiological property of vestibular neurons with undetermined functional significance. At the very least, CV is highly correlated with threshold to electrical stimulation in the intact vestibular labyrinth. If CV is also important for vestibular coding, then electrical stimulation strategies should be designed to restore relatively physiologic patterns of CV. Simulations using a stochastic model of primary afferent vestibular neurons reveal that this should be possible using combinations of low and high-rate pulsatile stimulation. They also demonstrate that differences in the number and independence of synaptic inputs can significantly affect CV.
Effects of rotation on the P13 mid-latency auditory evoked potential in Rat
Authors: Homma Yuko , Homma Yutaka , Teneud Luis , Skinner Robert D. , Dornhoffer John , Williams D. Keith , Garcia-Rill Edgar
Published: September 2021

The P13 mid-latency auditory evoked potential in Rat is a sleep state-dependent response thought to be equivalent to the human P50 potential, a measure of the output of the reticular activating system. The amplitude of these potentials can be considered a measure of level of arousal, while, using a paired stimulus paradigm, the degree of habituation of the responses also can be assessed. Different durations of rotation were found to reduce the amplitude of the P13 potential, which recovered in a duration-dependent manner. Different durations of rotation led to decreases in habituation of the P13 potential again in a duration-dependent manner. These results suggest that rotation may affect the level of arousal as well as habituation to repetitive sensory inputs. Such effects could be interpreted to imply the presence, following rotation of sufficient duration, of a deficit in sensory gating, or distractibility, and are relevant for the study of the effects of space motion sickness.
Training, transfer, and retention of three-dimensional spatial memory in virtual environments
Authors: Richards Jason T. , Oman Charles M. , Shebilske Wayne L. , Beall Andrew C. , Liu Andrew , Natapoff Alan
Published: September 2021

Human orientation requires one to remember and visualize spatial arrangements of landmarks from different perspectives. Astronauts have reported difficulties remembering relationships between environmental landmarks when imagined in arbitrary 3D orientations. The present study investigated the effects of strategy training on humans' 1) ability to infer their orientation from landmarks presented ahead and below, 2) performance when subsequently learning a different array, and 3) retention of configurational knowledge over time. On the first experiment day, 24 subjects were tested in a virtual cubic chamber in which a picture of an animal was drawn on each wall. Through trial-by-trial exposures, they had to memorize the spatial relationships among the six pictures around them and learn to predict the direction to a specific picture when facing any view direction, and in any roll orientation. Half of the subjects ("strategy group") were taught methods for remembering picture groupings, while the remainder received no such training ("control group"). After learning one picture array, the procedure was repeated in a second. Accuracy (% correct) and response time learning curves were measured. Performance for the second array and configurational memory of both arrays were also retested 1, 7, and 30 days later. Results showed that subjects "learned how to learn" this generic 3D spatial memory task regardless of their relative orientation to the environment, that ability and configurational knowledge was retained for at least a month, that figure rotation ability and field independence correlate with performance, and that teaching subjects specific strategies in advance significantly improves performance. Training astronauts to perform a similar generic 3D spatial memory task, and suggesting strategies in advance, may help them orient in three dimensions.
Recovery trajectories of vestibulopathic subjects after perturbations during locomotion
Authors: Wall C. , Oddsson L.I. , Patronik N. , Sienko K. , Kentala E.
Published: September 2021

We compared the mediolateral (M/L) responses to perturbations during locomotion of vestibulopathic (VP) subjects to those of controls. Eight subjects with unilateral vestibular loss (100% Reduced Vestibular Response from the caloric test) resulting from surgery for vestibular schwannoma and 11 controls were selected for this study. Despite their known vestibulopathy, all VP subjects scored within the normal range on computerized dynamic posturography Sensory Organization Tests. During gait, subjects were given surface perturbations of the right support-phase foot in two possible directions (forward-right and backward-left) at two possible magnitudes (5 and 10 cm) that were randomly mixed with trials having no perturbations. M/L stability was quantified by estimating the length of the M/L moment arm between the support foot and the trunk, and the M/L accelerations of the sternum and the head. The VP group had greater changes (p < 0.05) in their moment arm responses compared to controls. The number of steps that it took for the moment arm oscillations to return to normal and the variability in the moment arms were greater for the VP group. Differences in the sternum and head accelerations between VP and control groups were not as consistent, but there was a trend toward greater response deviations in the VP group for all 4 perturbation types. Increased response magnitude and variability of the VP group is consistent with an increase in their sensory noise of vestibular inputs due to the surgical lesion. Another possibility is a reduced sensitivity to motion inputs. This perturbation approach may prove useful for characterizing subtle vestibulopathies and similar changes in the human orientation mechanism after exposure to microgravity.
Sensorimotor aspects of high-speed artificial gravity: II. The effect of head position on illusory self motion
Authors: Mast Fred W. , Newby Nathaniel J. , Young Laurence R.
Published: September 2021

The effects of cross-coupled stimuli on the semicircular canals are shown to be influenced by the position of the subject's head with respect to gravity and the axis of rotation, but not by the subject's head position relative to the trunk. Seventeen healthy subjects made head yaw movements out of the horizontal plane while lying on a horizontal platform (MIT short radius centrifuge) rotating at 23 rpm about an earth-vertical axis. The subjects reported the magnitude and duration of the illusory pitch or roll sensations elicited by the cross-coupled rotational stimuli acting on the semicircular canals. The results suggest an influence of head position relative to gravity. The magnitude estimation is higher and the sensation decays more slowly when the head's final position is toward nose-up (gravity in the subject's head x-z-plane) compared to when the head is turned toward the side (gravity in the subject's head y-z-plane). The results are discussed with respect to artificial gravity in space and the possible role of pre-adaptation to cross-coupled angular accelerations on earth.
Effects of hypothermic anesthesia of the feet on vibration-induced body sway and adaptation
Authors: Stål F. , Fransson P.A. , Magnusson M. , Karlberg M.
Published: September 2021

The aim of this study was to investigate the significance of information from the plantar cutaneous mechanoreceptors in postural control and whether postural control could compensate for reduced cutaneous information by adaptation. Sixteen healthy subjects were tested with eyes open or eyes closed with hypothermic and normal feet temperature during posturography where body sway was induced by vibratory proprioceptive stimulation towards both calf muscles. The hypothermic anesthesia was obtained by cooling the subject's feet in ice water for 20 minutes. Body movements were evaluated by analyzing the anteroposterior and lateral torques induced towards the supporting surface by a force platform during the posturography tests.

The reduction of cutaneous sensor information from the mechanoreceptors of the feet significantly increased the vibration-induced torque variance mainly in the anteroposterior direction. However, the effects of disturbed mechanoreceptors information was rapidly compensated for through postural adaptation and torque variance was in level with that without anesthesia within 50 to 100 seconds of stimulation, both when standing with eyes open and eyes closed. Our findings suggest that somatosensory input from mechanoreceptors in the foot soles contribute significantly in maintaining postural control, but the sensory loss could be compensated for.
Eye-head coordination in darkness: Formulation and testing of a mathematical model
Authors: Ramat Stefano , Schmid Roberto , Zambarbieri Daniela
Published: September 2021

Passive head rotation in darkness produces vestibular nystagmus, consisting of slow and quick phases. The vestibulo-ocular reflex produces the slow phases, in the compensatory direction, while the fast phases, in the same direction as head rotation, are of saccadic origin. We have investigated how the saccadic components of the ocular motor responses evoked by active head rotation in darkness are generated, assuming the only available sensory information is that provided by the vestibular system.

We recorded the eye and head movements of nine normal subjects during active head rotation in darkness. Subjects were instructed to rotate their heads in a sinusoidal-like manner and to focus their attention on producing a smooth head rotation.

We found that the desired eye position signal provided to the saccadic mechanism by the vestibular system may be modeled as a linear combination of head velocity and head displacement information. Here we present a mathematical model for the generation of both the slow and quick phases of vestibular nystagmus based on our findings. Simulations of this model accurately fit experimental data recorded from subjects.
Eye movement responses to active, high-frequency pitch and yaw head rotations in subjects with unilateral vestibular loss or posterior semicircular canal occlusion
Authors: Gianna-Poulin Claire C. , Stallings Valerie , Black F. Owen
Published: September 2021

This study assessed the eye movement responses to active head rotation in six subjects with complete unilateral vestibular loss (UVL), five subjects with posterior canal plugging (PCP) and age- and sex-matched normal subjects. Subjects performed head rotations in the pitch and yaw planes at frequencies ranging from 2 to 6 Hz, while looking at an earth-fixed target. Vertical eye movement gains obtained in UVL, PCP and normal subjects were not significantly different. Vertical phases decreased with increasing head movement frequencies in both UVL and PCP subjects. Although this decrease produced significantly different vertical phases between UVL and normal subjects for head movements above 3.9 Hz, vertical phases in some normal subjects were similar to those obtained in UVL subjects. We conclude that active head oscillations in the pitch plane are not clinically useful for the detection of vertical canal impairment limited to one ear.

As expected, UVL subjects showed reduced horizontal gains, and eye velocity asymmetries during active head rotation in the yaw plane. Results in some PCP subjects suggested possible minor impairments of horizontal vestibulo-ocular reflexes.
Models of the mechanical sensitivity and growth of otoliths in fish
Authors: Kondrachuk Alexander V.
Published: September 2021

It has been suggested that, in the fish, the change of otolith mass during development under altered gravity conditions [1,2,3,4,5,6,24,25,36,37] and the growth of otoliths in normal conditions [22,23,26], are determined by feedback between otolith dynamics and the processes that regulate otolith growth. The hypothesis originates from an oscillator model of the otolith [30] in which otolith mass is one of the parameters. However, the validity of this hypothesis is not obvious and has not been experimentally verified. We tested this hypothesis by comparing the oscillator model with a simplified spatially distributed model of the otolith. It was shown that in the case of a spatially distributed fixation of the otolith plate (otoconial layer) to the macular surface, the mechanical sensitivity of the otolith does not depend on the total otolith mass nor on its longitudinal size. It is determined by otolith thickness, the Young's modulus and viscosity of gel layer of the growing otolith. These parameters may change in order to maintain otolith sensitivity under conditions (such as growth or altered gravity) that change the dynamics of otolith movement.
Unilateral examination of utricle and saccule function
Authors: Clarke A.H. , Schönfeld U. , Helling K.
Published: September 2021

Attention is directed towards the recently developed unilateral tests of saccular and utricular function. Together with the now widely used head-thrust test and the standard caloric test for semicircular canal function, these provide for a more comprehensive unilateral examination of labyrinth function. The efficacy of vestibular evoked myogenic potentials (VEMP) as a direct unilateral test of saccular function is currently being demonstrated in an increasing number of reports. Furthermore, the relevant neuronal pathways have been delineated in animal studies, so that all evidence points to the validity of the VEMP as a saccule-mediated response. Concerning utricular function, considerable headway has been made using the unilateral centrifugation paradigm. Testing is performed with a variable radius rotary chair with constant velocity rotation about the earth-vertical axis. Displacing the head by 3.5–4 cm from the rotation axis, the eccentrically positioned utricle is stimulated unilaterally by the resultant centrifugal force. This paradigm can be employed to elicit a utriculo-ocular response (UOR) or to permit measurement of the subjective visual vertical (SVV). More recently, it has also been demonstrated that testing during normal, on-centre yaw axis rotation is often sufficient to localise peripheral otolith dysfunction by means of SVV estimation. This test mode can be easily integrated into routine clinical testing. To illustrate the efficacy of such differential testing, the findings from two patients are presented that demonstrate for the first time an isolated unilateral utricular dysfunction.
Models for neurovestibular adaptation
Authors: Young Laurence R.
Published: September 2021

Dynamic models have played a more prominent role in the vestibular and oculomotor field than in any other branch of physiology. The ease of identification of input and output variables and the challenge of multi-loop, multi-axis adaptive control has attracted numerous modelers from engineering and shaped behavioral and neurophysiological experimental programs. In particular, the adaptive characteristics of the neurovestibular system have generated continuing speculation as to mechanisms. This treatment of adaptation and multi-sensor integration covers the development and application of such models, principally in the author's laboratory. It emphasizes the continuing relevance of both "model reference" and "error pattern recognition" notions of adaptive control.
Central distribution of vestibular afferents that innervate the anterior or lateral semicircular canal in the mongolian gerbil
Authors: Kevetter Golda Anne , Leonard Robert B. , Newlands Shawn D. , Perachio Adrian A.
Published: September 2021

The central distribution of afferents that innervate the crista ampullaris of the anterior or lateral semicircular canals was determined in gerbils following the direct injection of tracers into one sensory neuroepithelia. Labeled somata were scattered throughout the superior ganglion. The central distribution of fibers demonstrated extensive overlap. The central branch of afferents innervating either canal was located in the rostral part of the nerve. Nerve fibers divided into ascending and descending branches. Ascending branch ramifications terminated in the superior vestibular nucleus, the magnocellular and parvicellular medial vestibular nuclei, and the cerebellum. Cerebellar terminal areas include the flocculus, nodulus and uvula. Descending branch ramifications terminated in the caudal medial, parvicellular medial and descending vestibular nuclei, and the nucleus prepositus hypoglossi. Lateral canal afferents terminated sparsely in nucleus cuneatus. The anterior canal had sparse innervation in the paratrigeminal and gigantocellular reticular formation. This study has shown many similarities in the central distribution of fibers that innervate the anterior and lateral canals and a few areas of segregated input. Projections outside the vestibular nuclei are more extensive than previously determined, including afferents to prepositus hypoglossi, cochlear nuclei, and reticular formation. Projections to the flocculus appear as numerous as those to the vermis.
Chlorpheniramine for motion sickness
Authors: Buckey Jay C. , Alvarenga Donna , Cole Bernard , Rigas James R.
Published: September 2021

Background: Motion sickness remains a significant problem for travelers and for those involved in naval, aviation and space operations. Many motion sickness remedies are also sedating, making them undesirable in many settings. Methods: We studied chlorpheniramine as a potential motion sickness treatment. A placebo-controlled, double-blind, dose-ranging trial was performed to establish the most effective dose and the drug's effects on cognition. Eighteen normal, motion sickness susceptible subjects received placebo, low dose (4 mg) or high dose (12 mg) chlorpheniramine 3.5 hours before off-axis vertical rotation. Cognitive testing included a battery of objective and subjective tests performed before drug ingestion, at peak drug effect and following rotation. Results: Chlorpheniramine significantly increased the time in the chair compared to placebo at high dose (7.2 minutes to 11.7 minutes) and low dose (7.2 minutes to 10.2 minutes). Chlorpheniramine did not affect performance on objective cognitive tests. Subjects reported significantly more sleepiness and less alertness with high-dose chlorpheniramine, although they could not reliably determine when they had received active drug. Conclusion: Chlorpheniramine is effective and could be considered for use against motion sickness. Chlorpheniramine also has the potential to be administered transdermally.
Does vestibular damage cause cognitive dysfunction in humans?
Authors: Smith Paul F. , Zheng Yiwen , Horii Arata , Darlington Cynthia L.
Published: September 2021

For more than a decade, evidence from animal studies has suggested that damage to the vestibular system leads to deficits in spatial navigation which are indicative of impaired spatial learning and memory. More recently, direct evidence has emerged to demonstrate that humans with vestibular disorders exhibit a range of cognitive deficits that are not just spatial in nature, but also include non-spatial functions such as object recognition memory. Vestibular dysfunction has been shown to adversely affect attentional processes and increased attentional demands can worsen the postural sway associated with vestibular disorders. Recent MRI studies also show that humans with bilateral vestibular damage undergo atrophy of the hippocampus which correlates with their degree of impairment on spatial memory tasks. These results are consistent with those from animal studies and, together, suggest that humans with vestibular disorders are likely to experience cognitive dysfunction which is not necessarily related to any particular episode of vertigo or dizziness, and therefore may occur even in patients who are otherwise well compensated. These findings may be related to the observation that patients with vestibular deficits experience a high incidence of depression and anxiety disorders.
Synaptic ribbon plasticity, ribbon size and potential regulatory mechanisms in utricular and saccular maculae
Authors: Ross Muriel D. , Varelas Joseph
Published: September 2021

The mean number of synaptic ribbons in type II hair cells of the rat utricular macula increased significantly in weightlessness. In contrast, ribbon synapses of saccular type I hair cells displayed a significant decline early inflight and postflight, and a late numerical overshoot. Further study indicated that the saccular macula had less ultrastructural complexly than the utricular. Additionally, synaptic ribbons were statistically larger in type II hair cells of both maculae, apparently a locus-related scaling effect. A major new finding is that mitochondria in calyces and collateral terminals were linked to vesicles, tubules of smooth endoplasmic reticulum and cell membranes by filaments, forming mitochondrial complexes (MCs). MCs predominated basally in the calyx where calyceal/type I hair cell borders were bound by filaments; at calyceal invaginations of type I hair cells; in calyces and collaterals near synaptic ribbon sites; and in collaterals near reciprocal synapses. MCs may participate in feedback mechanisms at these locations to help regulate synaptic ribbon activity and plasticity in altered gravitational environments.
Effect of angular acceleration on the localization performance of a remembered target
Authors: Schmäl Frank , Glitz Barbara , Thiede Oliver , Stoll Wolfgang
Published: September 2021

Both the influence of a remembered “earth-fixed” target (RT) on the vestibulo-ocular reflex and the effect of “unilateral cold caloric vestibular stimulation” on the localization of a RT have previously been proved. As “unilateral caloric stimulation” is not a physiological stimulus, the aim of the present study was to analyze whether even physiological “bilateral vestibular stimulation” (rotation) is able to affect the RT position. The pointing error (PE) towards an RT both without and following angular acceleration was investigated in 24 healthy volunteers. Postrotatory nystagmus response was recorded by electronystagmography. Evaluation parameters were “nystagmus frequency”, “total amplitude” and “velocity of the slow phase”; the horizontal and vertical PE. The fixation of an RT led to a significant reduction of about 28% in nystagmus amplitude compared to the test condition in darkness. “After rotatory stimulation” a systematic horizontal PE in the direction of the fast phase of the postrotatory nystagmus (direction of “illusory self-rotation”) occurred and the magnitude of this PE increased significantly compared to the test situation “without vestibular stimulation”, but showed only a non-uniform negative correlation with two of the nystagmus parameters. It has to be concluded that “after rotatory stimulation”, in contrast to “unilateral cold caloric vestibular stimulation”, the subjective sense of “illusory self-motion” leads to a horizontal PE in the direction of the nystagmus fast phases.
VEMPs and dynamic posturography after intratympanic gentamycin in Menière's disease
Authors: Picciotti Pasqualina M. , Fiorita Antonella , Di Nardo Walter , Quaranta Nicola , Paludetti Gaetano , Maurizi Maurizio
Published: September 2021

In this study, we investigated whether vestibular evoked myogenic potentials (VEMPs) and dynamic posturography (DP) are useful in the evaluation of the vestibular function in patients affected by active monoaural Menière's disease (MD) treated with intratympanic gentamycin. Twelve subjects affected by monoaural MD were treated with weekly intratympanic injections of 0.5 ml of gentamycin at a concentration of 20 mg/ml. VEMPs were used to test saccular function, while postural control was analyzed by DP. The results obtained with these two techniques were compared with those obtained by using bithermal caloric test. The mean follow-up was 15.3 months (6–28 months). Therapy resulted in complete absence of the caloric response in six subjects (50) and in caloric test-induced asymmetry in the remaining individuals, ranging from 83 to 27. At follow-up, eleven patients (91.6%) were free of vertigo, while one patient had two vertigo spells 9 months after treatment. Before treatment, VEMPs were present in the affected ear of eleven patients. After treatment VEMPs were absent in all the patients. At the end of follow-up, reappearance of VEMPs was observed in two patients, with no changes in latency values and amplitude ratio. DP demonstrated a reduction of the Composite Score (CS) one week after therapy, with a prevalent reduction of the vestibular component. After 6 months, there was an improvement of the CS and, in particular, of the vestibular component. The present study demonstrates that bithermal caloric test and VEMPs allow for the functional evaluation of both the horizontal semicircular canal and the sacculus, suggesting that these techniques might be used together to monitor the efficacy of intratympanic gentamycin therapy. In addition, our data indicate that DP might provide important information on compensation phenomena and show that intratympanic gentamycin can improve postural control in MD patients.
Full-body gaze control mechanisms elicited during locomotion: Effects of VOR adaptation
Authors: Mulavara A.P. , Houser J. , Miller C. , Bloomberg J.J.
Published: September 2021

We have previously shown that multiple, interdependent, full- body sensorimotor subsystems aid gaze stabilization during locomotion. In the present study we investigated how the full-body gaze control system responds following exposure to visual-vestibular conflict known to adaptively modify vestibulo-ocular reflex (VOR) function. Subjects (n = 14) walked (6.4 km/h) on a motorized treadmill before and after they were exposed to 0.5X minifying lenses worn for 30 minutes during self-generated sinusoidal vertical head rotations performed while seated. Results indicate that, following the exposure the major changes that subjects showed were to: 1) decrease the amplitude of head pitch and vertical translation of the torso movement with respect to space; 2) increase the amount of knee and ankle flexion during the initial stance phase of the gait cycle. A correlation analysis showed that: 1) changes in the head pitch significantly co-varied with that of the vertical torso translation 2) changes in the knee flexion significantly co-varied with that of the ankle flexion during the initial stance phase of the gait cycle 3) changes in the vertical torso translation significantly co-varied with that of the ankle flexion during the initial stance phase of the gait cycle. Thus we infer that the changes in the magnitude after VOR adaptation in comparison to their pre adaptation responses serve to aid gaze stabilization during locomotion. The significant covariation of the changes between subsystems provides further evidence that the full body contributes to gaze stabilization during locomotion, and its different functional elements are subject to adaptive reorganization following exposure to visual-vestibular conflict.
Vestibular function in migraine-related dizziness: A pilot study
Authors: Furman Joseph M. , Sparto Patrick J. , Soso Michael , Marcus Dawn
Published: September 2021

Migraine-related dizziness (MRD) refers to a disorder in which vestibular symptoms are an integral part of migraine symptomatology. The purpose of this study was to better define the pathophysiology of MRD, which is incompletely understood and to generate hypotheses regarding MRD by assessing the semicircular canal-ocular reflex, the otolith-ocular reflex, visual-vestibular interaction, vestibulo-spinal function, and visually induced postural sway. Subjects included five subjects with MRD, five subjects with migraine without dizziness, and five headache-free controls. Subjects with migraine were tested interictally. Results indicated that the mean gain of the semicircular canal-ocular reflex during both sinusoidal and constant velocity rotation was reduced in subjects with MRD. No changes were noted in the dynamics of the semicircular canal-ocular reflex. The otolith-ocular reflex, assessed with constant velocity OVAR, indicated that subjects with MRD showed a larger modulation component. No group differences were found in the bias component during constant velocity OVAR, nor in semicircular canal-otolith interaction or visual-vestibular interaction. Computerized dynamic posturography indicated that subjects with MRD demonstrated a surface-dependent pattern. Postural sway during optic flow indicated that subjects with MRD swayed more than the other subjects. We hypothesize that competing processes of serotonergic excitation and inhibition alter central vestibular pathways differently for semicircular canal vs. otolithic responses and for vestibulo-ocular vs. vestibulo-spinal pathways.
Subjective visual horizontal in the upright posture and asymmetry in roll-tilt perception: Independent measures of vestibular function
Authors: Tribukait Arne
Published: September 2021

The subjective visual horizontal (SVH) was measured in the upright position and at 10, 20, and 30 degrees of head and body tilt to the right and left. Normal subjects (n=25) were tested on two separate occasions with an interval of 1–14 days. Test variables considered were the SVH in the upright position, the perception of tilt to the right and left, calculated on the basis of the SVH in the upright and tilted positions, and the asymmetry in tilt perception. There was no correlation between the perception of tilt to the right and to the left r=0.10). Neither was there any correlation between the SVH in the upright position, representing a resting asymmetry, and the asymmetry in tilt perception, i.e. the response asymmetry (r=0.17). However, for each variable, there was a high correspondence between data obtained at test and retest (r ranged from 0.68 to 0.89, p<0.001), suggesting that the independence between variables is not due to noise. Findings are discussed taking into consideration the possible roles of otoliths and semicircular canals in the formation of the SVH. In an attempt to explain the independence between the two measures of asymmetry it is hypothesized that while the otoliths must be essential for the perception of static lateral tilt, the SVH in the upright position to a considerable degree reflects semicircular canal function.
Development of a vibrotactile tasking device for use in vestibular assessment
Authors: King John E. , González Jorge E. , Fuller Michael I.
Published: September 2021

The purpose of this study was to design an automated mental alerting task that could be utilized when performing vestibular testing on a broad range of patient populations, including certain difficult-to-test populations, such as the hard-of-hearing. A device was developed that utilized vibrotactile stimuli output to two vibrators placed on the subject's left leg, and responded to activation of two momentary pushbuttons controlled by the subjects. Fourteen normal-hearing subjects without history or symptoms of vestibular involvement participated. Each participant underwent three mental-alerting conditions, defined as no task, verbal task, or vibrotactile task. Each condition involved four irrigations of the ear canals, two with warm water and two with cool water. The resultant nystagmus was recorded and analyzed using four measures to compare the effect of the mental alerting task condition. No significant difference was found between verbal and vibrotactile alerting both of which provided better responses than the no alerting task (F=8.443; df=2,13; p=0.001). Between-subjects analysis showed that the number of gaps, which are undesirable periods of absent nystagmus during test recordings, was smallest for the verbal and vibrotactile tasks, and largest for the no task condition. Overall, the results showed that the vibrotactile tasking device (VTD) is an effective alternative means of providing mental alerting during vestibular testing, specifically that of caloric examination.
Vertical skew due to changes in gravitoinertial force: A possible consequence of otolith asymmetry
Authors: Karmali Faisal , Ramat Stefano , Shelhamer Mark
Published: September 2021

During the alternating enhanced and reduced "gravity" levels of parabolic flight, subjects noted that a horizontally eccentric point target viewed binocularly in darkness seemed to split into two targets with vertical divergence. The amount of perceived divergence seemed to depend on instantaneous g level. This perceptual observation suggested a vertical misalignment of the eyes (vertical skew), dependent on the magnitude of g level sensed by the otoliths. While performing a different experiment during parabolic flight we recorded binocular eye position and analyzed these data to corroborate the behavioral observations. Records were obtained from seven trials in five subjects, containing eye alignment in both 0 g and 1.8 g. The recordings confirm the presence of vertical skew that changed with g level. "Skew-differential" was quantified for each trial as the difference in vertical skew from 0 g to 1.8 g. Mean skew-differential was 1.37°; the largest was 2.57°. Statistical significance was assessed using the student t-test and the more correct and stringent Generalized Estimating Equations (GEE). The observed skew is equivalent to a mild strabismus, which is known to result in diplopia. The underlying mechanism may be an asymmetry between the otolith organs on either side, which is centrally compensated in 1 g, but is inappropriately compensated in other gravitational fields. If equivalent amounts of vertical skew were to occur during changes in g level during dynamic phases of flight in high-performance aircraft or space shuttle reentry, the impact on visual fixation might be detrimental to piloting performance.
The effect of alcohol ingestion on ocular counterrolling
Authors: Markham Charles H. , Diamond Shirley G.
Published: September 2021

Nineteen normal subjects underwent two naso-occipital rotations to 90° right and left ear down in our standard ocular counterrolling (OCR) protocol. Both eyes were videotaped. Following two rotations, subjects drank 90~ml vodka in 180 ml orange juice; and in about 20 min, when blood alcohol levels reached 0.04–0.09%, the protocol was repeated. An SMI videooculography system provided measurements. Results showed that amplitude of OCR was significantly decreased after alcohol ingestion; smoothness was significantly increased after alcohol, similar to alcohol's effect on essential tremor. Although disconjugacy was not significantly different in the two conditions when the entire trials were examined, the latter portions of the post-alcohol trials did show significant disconjugacy, similar to earlier findings in vestibular-defective patients whose OCR deficits were apparent only in the final segments of the rotation trials. We postulate the results are due to alcohol's action on cerebellar GABAergic Purkinje cells projecting to vestibular nuclei.
Vestibulo-ocular function in anxiety disorders
Authors: Furman Joseph M. , Redfern Mark S. , Jacob Rolf G.
Published: September 2021

Previous studies of vestibulo-ocular function in patients with anxiety disorders have suggested a higher prevalence of peripheral vestibular dysfunction compared to control populations, especially in panic disorder with agoraphobia. Also, our recent companion studies have indicated abnormalities in postural control in patients with anxiety disorders who report a high degree of space and motion discomfort. The aim of the present study was to assess the VOR, including the semicircular canal-ocular reflex, the otolith-ocular reflex, and semicircular canal-otolith interaction, in a well-defined group of patients with anxiety disorders. The study included 72 patients with anxiety disorders (age 30.6 +/− 10.6 yrs; 60 (83.3% F) and 29 psychiatrically normal controls (age 35.0 +/minus; 11.6 yrs; 24 (82.8% F). 25 patients had panic disorder; 47 patients had non-panic anxiety. Patients were further categorized based on the presence (45 of 72) or absence (27 of 72) of height phobia and the presence (27 of 72) or absence (45 of 72) of excessive space and motion discomfort (SMD). Sinusoidal and constant velocity earth-vertical axis rotation (EVAR) was used to assess the semicircular canal-ocular reflex. Constant velocity off-vertical axis rotation (OVAR) was used to assess both the otolith-ocular reflex and static semicircular canal-otolith interaction. Sinusoidal OVAR was used to assess dynamic semicircular canal-otolith interaction. The eye movement response to rotation was measured using bitemporal electro-oculography. Results showed a significantly higher VOR gain and a significantly shorter VOR time constant in anxiety patients. The effect of anxiety on VOR gain was significantly greater in patients without SMD as compared to those with SMD. Anxiety patients without height phobia had a larger OVAR modulation. We postulate that in patients with anxiety, there is increased vestibular sensitivity and impaired velocity storage. Excessive SMD and height phobia seem to have a mitigating effect on abnormal vestibular sensitivity, possibly via a down-weighting of central vestibular pathways.
Modification of compensatory saccades after aVOR gain recovery
Authors: Schubert Michael C. , Migliaccio Americo A. , Santina Charles C. Della
Published: September 2021

The recruitment of extra-vestibular mechanisms to assist a deficient angular vestibulo-ocular reflex (aVOR) during ipsilesional head rotations is well established and includes saccades of reduced latency that occur in the direction of the lesioned aVOR, termed compensatory saccades (CS). Less well known is the functional relevance of these unique saccades. Here we report a 42 y.o. male diagnosed with right unilateral vestibular hypofunction due to vestibular neuronitis who underwent a vestibular rehabilitation program including gaze stabilization exercises. After three weeks, he had a significant improvement in his ability to see clearly during head rotation. Our data show a reduction in the recruitment and magnitude of CS as well as improved peripheral aVOR gain (eye velocity/head velocity) and retinal eye velocity. Our data suggest an inverse, dynamic relationship between the recruitment of CS and the gain of the aVOR.
Vestibular nuclear complex in cattle: Topography, morphology, cytoarchitecture and lumbo-sacral projections
Authors: Grandis Annamaria , Bombardi Cristiano , Travostini Beatrice , Gentile Arcangelo , Joechler Monica , Pisoni Luciano , Chiocchetti Roberto
Published: September 2021

The topography and the main characteristics of the vestibular nuclear complex (VNC) in cattle have been studied in serially transversally cut Nissl and Gles-stained sections. By using computerized image analysis software, the cell size, the maximum and minimum diameter of the neurons of each vestibular nucleus were obtained. These parameters were statistically analyzed by comparing the cell population from different nuclei and different parts of each nucleus. Furthermore, in order to investigate the lumbo-sacral projections, the fluorescent tracer Fast Blue was injected into the L6-S1 spinal cord of three calves. Among the vestibular nuclei, the superior was the least extensive rostro-caudally, the medial was the most extensive and contained the smallest cells, the lateral showed the largest neurons, and the descending nucleus contained cells of intermediate size which decreased in a rostrocaudal direction. Concerning the lumbo-sacral projections of the bovine VNC, the present study showed that only the fibers coming from the lateral vestibular nucleus reached the L6-S1 spinal cord. The labelled neurons were most heavily concentrated in the dorsal portion of this nucleus, but scattered neurons were also observed throughout the entire extension of the nucleus. The differences between the descriptions of cattle and other species were described.