The delay of the oculogravic illusion

Previous measures of roll-tilt sensation during combined angular and linear acceleration during off-center rotation have found a heading-dependent delay in reaching a stable sensory value. This delay has been attributed to sensory conflict between the canal and otolith signals. Another possibility is that the visual indicator used to measure this sensation may have been responsible for the heading-dependent difference. This study used a somatosensory task, which is free from such artifacts and still showed a significant heading-dependent delay. We conclude that in analyzing canal-otolith interaction it is necessary to take into account the direction of the linear acceleration with respect to the activated canal.     

The subjective horizontal at different angles of roll-tilt in patients with unilateral vestibular impairment

The subjective visual horizontal is mainly dependent on the otolithic system. A group of 11 patients with sudden unilateral vestibular impairment were asked to set a dimly illuminated bar according to their subjective horizontal when they were seated upright and tilted 10, 20, and 30 degrees to the right and left in a completely darkened room (Bias test). The patients were examined within 1 week, after 3 and 6 weeks, and 9 patients consented to the 11-week follow-up. The results were compared with ENG examinations. In the acute stage of the disease all patients, when they were in upright position, set the light bar tilted towards the affected side. At roll tilt to the affected side, 9 of the 11 patients set the light bar in the same direction as their body tilt (undercorrection). At a tilt to the unaffected side 6 of the 11 patients made an undercorrection. For the group of patients the magnitude of undercorrection was larger at tilt to the affected side than to the unaffected side. The patients' ability to correctly align the light bar with the true horizontal gradually improved but was found normal in both upright and tilted positions in only three of the nine patients at the last follow-up. In four of the six patients who still demonstrated pathologic results, these were met only in tilted positions. No significant correlation was found between the intensity of spontaneous nystagmus or the degree of caloric side difference and the deviation in setting of the light bar in upright or tilted positions. The large asymmetric perceptual responses at tilt found at onset might be explained by the two-directional organisation of the utricle.     

Dynamic characteristics of vestibular-driven compensatory fin movements of the dogfish

Compensatory pectoral fin reflexes were studied in decerebrate dogfish subjected to sinusoidal oscillation (0.01-1.0 Hz). At 0.01 Hz the peak response of the depressor muscle was in phase with head position. At higher frequencies the phase advanced and at 1 Hz approached that of maximum angular velocity. Peak response amplitude was steady from 0.01 to 0.07 Hz but thereafter increased markedly. We suggest that the high frequency response depends upon vertical semicircular canal input.     

Saccule contribution to immediate early gene induction in the gerbil brainstem with posterior canal galvanic or hypergravity stimulation

Immunolabeling patterns of the immediate early gene-related protein Fos in the gerbil brainstem were studied following stimulation of the sacculus by both hypergravity and galvanic stimulation. Head-restrained, alert animals were exposed to a prolonged (1 h) inertial vector of 2 G (19.6 m/s²) head acceleration directed in a dorso-ventral head axis to maximally stimulate the sacculus. Fos-defined immunoreactivity was quantified, and the results compared to a control group. The hypergravity stimulus produced Fos immunolabeling in the dorsomedial cell column (dmcc) of the inferior olive independently of other subnuclei. Similar dmcc labeling was induced by a 30 min galvanic stimulus of up to −100 μA applied through a stimulating electrode placed unilaterally on the bony labyrinth overlying the posterior canal (PC). The pattern of vestibular afferent firing activity induced by this galvanic stimulus was quantified in anesthetized gerbils by simultaneously recording from Scarpa's ganglion. Only saccular and PC afferent neurons exhibited increases in average firing rates of 200–300%, suggesting a pattern of current spread involving only PC and saccular afferent neurons at this level of stimulation. These results suggest that alteration in saccular afferent firing rates are sufficient to induce Fos-defined genomic activation of the dmcc, and lend further evidence to the existence of a functional vestibulo-olivary-cerebellar pathway of adaptation to novel gravito-inertial environments.     

Central projections of the vestibular nerve: a review and single fiber study in the Mongolian gerbil

The primary purpose of this article is to review the anatomy of central projections of the vestibular nerve in amniotes. We also report primary data regarding the central projections of individual horseradish peroxidase (HRP)-filled afferents innervating the saccular macula, horizontal semicircular canal ampulla, and anterior semicircular canal ampulla of the gerbil.

In total, 52 characterized primary vestibular afferent axons were intraaxonally injected with HRP and traced centrally to terminations. Lateral and anterior canal afferents projected most heavily to the medial and superior vestibular nuclei. Saccular afferents projected strongly to the spinal vestibular nucleus, weakly to other vestibular nuclei, to the interstitial nucleus of the eighth nerve, the cochlear nuclei, the external cuneate nucleus, and nucleus y.

The current findings reinforce the preponderance of literature. The central distribution of vestibular afferents is not homogeneous. We review the distribution of primary afferent terminations described for a variety of mammalian and avian species. The tremendous overlap of the distributions of terminals from the specific vestibular nerve branches with one another and with other sensory inputs provides a rich environment for sensory integration.     

Vestibulo-ocular reflex of the squirrel monkey during eccentric rotation with centripetal acceleration along the naso-occipital axis

The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in four male squirrel monkeys. Monkeys were rotated in the dark at 200°/s, centrally or 79 cm off-axis, with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's position relative to the centripetal acceleration (facing center or back to center) had a dramatic influence on the VOR. These studies show that a torsional response was always elicited that acted to shift the axis of eye rotation toward alignment with gravito-inertial force. On the other hand, a slow phase downward vertical response usually existed, which shifted the axis of eye rotation away from the gravito-inertial force. These findings were consistent across all monkeys. In another set of tests, the same monkeys were rapidly tilted about their interaural (pitch) axis. Tilt orientations of 45° and 90° were maintained for 1 min. Other than a compensatory angular VOR during the rotation, no consistent eye velocity response was ever observed during or following the tilt. The absence of any response following tilt proves that the observed torsional and vertical responses were not a positional nystagmus. Model simulations qualitatively predict all components of these eccentric rotation and tilt responses. These simulations support the conclusion that the VOR during eccentric rotation may consist of two components: a linear VOR and a rotational VOR. The model predicts a slow phase downward, vertical, linear VOR during eccentric rotation even though there was never a change in the force aligned with monkey's spinal (Z) axis. The model also predicts the torsional components of the response that shift the rotation axis of the angular VOR toward alignment with gravito-inertial force.     

Differing response properties of cervical and ocular vestibular evoked myogenic potentials evoked by air-conducted stimulation

ObjectiveTo determine the amplitude changes of vestibular evoked myogenic potentials (VEMPs) recorded simultaneously from the neck (cVEMPs) and eyes (oVEMPs) in response to 500 Hz, 2 ms air-conducted sound pips over a 30 dB range.MethodsFifteen healthy volunteers (mean age 29, range 18–57 years old) and one patient with unilateral superior canal dehiscence (SCD) were studied. The stimulus was reduced in increments to 105 dB pSPL for the normals (81 dB pSPL for the SCD patient). A statistical criterion was used to detect responses.ResultsIpsilateral (i-p13/n23) and contralateral (c-n12/p24/n30) peaks for the cVEMP montage and contralateral (c-n10/p16/n21) and ipsilateral (i-n13) peaks for the oVEMP montage were present for the baseline intensity. For the lowest intensity, 6/15 subjects had responses for the i-p13 cVEMP potential and 4/15 had c-n10 oVEMP responses. The SCD patient showed larger responses for nearly all intensities. The cVEMP potentials were generally well fitted by a power law relationship, but the oVEMP c-n10, p16 and n21 potentials showed a significant increase in gradient for the higher intensities.ConclusionMost oVEMP and cVEMP responses follow a power law relationship but crossed oVEMP responses showed a change in gradient above a threshold.SignificanceThe pattern of response to AC stimulation may be a property of the pathways underlying the potentials.     

A comparison of vestibular and auditory phenotypes in inbred mouse strains

The purposes of this research were to quantify gravity receptor function in inbred mouse strains and compare vestibular and auditory function for strain- and age-matched animals. Vestibular evoked potentials (VsEPs) were collected for 19 inbred strains at ages from 35 to 389 days old. On average, C57BL/6J (35 to 190 days), BALB/cByJ, C3H/HeSnJ, CBA/J, and young LP/J mice had VsEP thresholds comparable to normal. Elevated VsEP thresholds were found for elderly C57BL/6J, NOD.NONH2(kb), BUB/BnJ, A/J, DBA/2J, NOD/LtJ, A/WySnJ, MRL/MpJ, A/HeJ, CAST/Ei, SJL/J, elderly LP/J, and CE/J. These results suggest that otolithic function varies among inbred strains and several strains displayed gravity receptor deficits by 90 days old. Auditory brainstem response (ABR) thresholds were compared to VsEP thresholds for 14 age-matched strains. C57BL/6J mice (up to 190 days) showed normal VsEPs with normal to mildly elevated ABR thresholds. Four strains (BUB/BnJ, NOD/LtJ, A/J, elderly LP/J) had significant hearing loss and elevated VsEP thresholds. Four strains (DBA/2J, A/WySnJ, NOD.NONH2(kb), A/HeJ) had elevated VsEP thresholds (including absent VsEPs) with mild to moderate elevations in ABR thresholds. Three strains (MRL/MpJ, Ce/J, SJL/J) had significant vestibular loss with no concomitant hearing loss. These results suggest that functional change in one sensory system does not obligate change in the other. We hypothesize that genes responsible for early onset hearing loss may affect otolithic function, yet the time course of functional change may vary. In addition, some genetic mutations may produce primarily gravity receptor deficits. Potential genes responsible for selective gravity receptor impairment demonstrated herein remain to be identified.     

The role of Smad4 in vestibular development in mice

The regulation of the bone morphogenetic protein (BMP) signal transduction pathway is important in the development of the inner ear and vestibular system. We reported previously that small mothers against decapentaplegic homolog-4 (Smad4) is required for inner ear cochlear development and normal auditory function in mammals; however, the distribution and functional mechanisms of Smad4 at various stages of vestibular development remained unclear. To investigate the relationship between the Smad4 gene and vestibular organ development, we measured changes in the expression of BMP4 and Smad4 during vestibular development in C57BL/6 mice. In addition, vestibular structures, pathologic changes, and the vestibular function of chondrocyte-specific Smad4 knockout mice were compared to those of the control group. We found that the expression of Smad4 in the inner ear was delayed compared with that of BMP4. Moreover, chondrocyte-specific Smad4 knockout homozygous mice showed stunted growth and partial vestibular deformities, but it showed less histologic changes in the vestibular end-organs and saccule dysfunction. These results suggest that Smad4 participates in late-stage shaping of the configuration of the vestibule and development of vestibular functional, but a Smad4-independent pathway for the inner ear vestibular BMP4 signal transduction could not be rule out.     

The effect of alcohol on cervical and ocular vestibular evoked myogenic potentials in healthy volunteers

ObjectiveWe investigated the effect of alcohol on the cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs). As alcohol produces gaze-evoked nystagmus (GEN), we also tested the effect of nystagmus independent of alcohol by recording oVEMPs during optokinetic stimulation (OKS).MethodsThe effect of alcohol was tested in 14 subjects over multiple rounds of alcohol consumption up to a maximum breath alcohol concentration (BrAC) of 1.5‰ (mean 0.97‰). The effect of OKS was tested in 11 subjects at 5, 10 and 15 deg/sec.ResultsoVEMP amplitude decreased from baseline to the highest BrAC level by 27% (range 5–50%, P < 0.001), but there was no significant effect on oVEMP latency or cVEMP amplitude or latency. There was a significant negative effect of OKS on oVEMP amplitude (16%, P = 0.006).ConclusionsWe found a selective effect of alcohol on oVEMP amplitude, but no effect on the cVEMP. Vertical nystagmus elicited by OKS reduced oVEMP amplitude.SignificanceAlcohol selectively affects oVEMP amplitude. Despite the effects of alcohol and nystagmus, both reflexes were reliably recorded in all subjects and conditions. An absent response in a patient affected by alcohol or nystagmus indicates a vestibular deficit.     

The primal role of the vestibular system in determining musical rhythm

Previous studies have indicated that physical movement on either every second or on every third beat of an unaccented auditory rhythm pattern can disambiguate whether it is perceived in duple time as a march or in triple time as a waltz. Here we demonstrate that this disambiguation can also be accomplished by direct galvanic stimulation of the vestibular system. The galvanically induced sensation, without any actual movement, that the head moved from side to side on either every second or on every third beat of the ambiguous auditory rhythm pattern strongly biased whether adults perceived it as being in duple or in triple time. These results imply that the vestibular system plays a primal role in the perception of musical rhythm.     

Thresholds for detection of motion direction during passive lateral whole-body acceleration in normal subjects and patients with bilateral loss of labyrinthine function

To investigate the effect of velocity, acceleration, and gradient of acceleration on self-motion perception, thresholds for detection of direction of whole-body interaural acceleration were determined for various stimulus profiles. For acceleration steps, acceleration thresholds at 67% correct detection of motion direction were similar for eight normals (mean 4.84 cm/s² (range 2.9–6.3), peak GRADIENT = 22 cm/s²) and five labyrinthine-defective subjects (mean 5.65 cm/s² (4.85–6.6), peak GRADIENT = 25 cm/s²). Velocity thresholds were 7.93 cm/s for a proportion of correct responses of 73% for normals and 9.67 cm/s for 69% of correct detection for avestibular subjects. For linear and parabolic accelerations, high intersubject variability was observed both among nine normals and three labyrinthine-defective subjects. Mean normal and avestibular subjects' acceleration thresholds for 74% of correct responses were respectively 12.1 cm/s² (7.3–20.4) and 16.4 cm/s² (13.2–20) for a ramp with gradient of ACCELERATION = 2.8 cm/s³, 19.2 cm/s² (10.4–35.3) and 28.2 cm/s² (21.4–32.8) for a ramp with GRADIENT = 7.9 cm/s³ and 16.7 cm/s² (10.5–25) and 20.6 cm/s² (18.4–24.2) for a parabola with second DERIVATIVE = 1.52 cm/s⁴. The corresponding velocity thresholds for normals were 21.2 cm/s (5.2–50.3), 22.0 cm/s (7–56.6), and 22.2 cm/s (9.5–43.7). The lowest thresholds were obtained for acceleration steps indicating that a high acceleration gradient facilitates motion perception. For linear and parabolic accelerations, motion perception seemed to follow an integration of acceleration, but a high intersubject variability was observed. For all stimuli, the range of thresholds for normals and avestibular subjects overlapped showing that detection of motion was not a sole prerogative of the otoliths but could also be performed using somatosensory cues.     

Orientation of the semicircular canals in rat

The orientation of the rat semicircular canals was determined using one of two techniques. Null point analysis was used to define physiologically the planar equations of the anterior (n = 15) and posterior canals (n = 15); equations for the horizontal canal (n = 19) were determined using an anatomical dissection technique. Canal orientation was defined with respect to stereotaxic coordinate system and, for comparison, relative to head position during freeze (startle) behavior. Results show that ipsilateral canal planes are orthogonal within 4-8 degrees, and pairs of right-left synergistic pairs are essentially co-planar. The horizontal canals are inclined upwards 35 degrees with respect to the horizontal plane, but a head position of 43 degrees nose-down was determined to produce near optimal horizontal canal and minimal vertical canal activation with horizontal rotation. Finally, a loud or unexpected auditory stimulus initiates a freeze (startle) response in rat characterized by an transient followed by a sustained head position lasting several seconds. Transients are complete within 300-400 ms. Thereafter, the head becomes momentarily stabilized in the startle position which averaged 14 +/- 8 degrees (nose-down with respect to horizontal stereotaxic zero) across the population (n = 14). The response habituated only slightly, but the final position was sufficiently variable so as to limit the usefulness of the freeze (startle) position as a reference of semicircular canal position in the rat.     

The influence of gravity on horizontal and vertical vestibulo-ocular and optokinetic reflexes in the rabbit

The influence of the linear acceleration of gravity on the vertical and horizontal vestibulo-ocular reflexes (VVOR, HVOR) as well as the vertical and horizontal optokinetic reflexes (VOKR, HOKR) has been examined in rabbits. Rabbits were mounted in a biaxial rate table in front of a rear projection tangent screen. Eye movements were measured with a light projection technique. The HVOR, VVOR, HOKR and VOKR were measured in rabbits which were maintained both prone and supine. The gain of the HVOR for the supine orientation was reduced at all frequencies tested (0.01-0.80 Hz). Similarly there was a reduction in the gain of the HOKR. By contrast, the gain of the VVOR in the supine orientation was enhanced over a lower range of frequencies (0.02-0.04 Hz) and reduced at higher frequencies (0.10-0.80 Hz). The gain of the VOKR was not reduced in the supine orientation. The range of eye positions over which compensatory eye movements occurred was restricted in the supine orientation. The altered orientation of the medio-laterally polarized hair cells of the utricular maculae with respect to gravity in the supine orientation may cause postural instability and facilitate 'righting reflexes'. A reduction in the gains of the HVOR, VVOR and HOKR caused by linear accelerations in the sagittal plane during locomotion may decrease automatic postural responses during certain movements in which these automatic postural adjustments would not necessarily be adaptive.     

前庭性偏头痛的眼震视图表现及诊断价值

目的比较前庭性偏头痛(VM)和健康受试者的眼震视图(VNG)表现,明确VNG检查在VM中的诊断价值.方法前瞻性连续纳入2018年8月至2019年8月在新乡医学院附属人民医院神经内科就诊的VM患者55例和体检中心健康受试者45例,所有患者及健康受试者在条件允许下行VNG检查,包括视动性试验(扫视试验、平稳跟踪试验、视动性试验)、前庭功能试验(温度试验、摇头眼震)、自发性眼震、诱发性眼震检查(静态位置性试验).采用χ^2检验比较两组之间VNG结果的差异.结果VM组与健康受试者组之间人口统计学差异无统计学意义(均P>0.05).扫视试验:VM组有17例(30.9%)异常,健康受试者组异常例数3例(6.7%;χ^2=9.091,P<0.05);平稳跟踪实验:VM组异常20例(36.4%),健康受试者组异常5例(11.1%;χ^2=8.418,P<0.05);视动性眼震检查:VM组异常例数24例(43.6%),健康受试者组异常例数6例(13.3%;χ^2=10.823,P<0.05);温度试验:VM组有13例(23.6%)异常,健康受试者组中异常2例(3.6%;χ^2=7.150,P<0.05);摇头眼震:VM组有11例(20.0%)异常,健康受试者组异常2例(3.6%;χ^2=5.295,P<0.05);自发性眼震检查:VM组中异常10例(18.2%),健康受试者组异常4例(8.9%;χ^2=1.775,P>0.05);静态位置性眼震检查:VM组共有22例(40.0%)异常,健康受试者组中共有7例异常(16.5%;χ^2=7.183,P<0.05).结论VM组的总VNG检查异常率高于健康受试者组,说明VNG检查有助于VM的诊断,且其表现提示VM患者中枢及外周均有损害的迹象.     

Effects of hypergravity on the morphological properties of the vestibular sensory epithelium. II. Life-long exposure of rats including embryogenesis

Rats were exposed to a hypergravity (HG) level of 2.5 x g from conception until the age of 14 weeks. The vestibular epithelia of four of these animals and four control animals were immunohistochemically labeled for actin and tubulin. The apical cross-sectional area of epithelial cells of HG exposed rats appeared to be larger in all end organs. Area increase was 7.0% in the utricle (p<0.005) and 8.2% in the crista (p<0.001). Hair cells and supporting cells appeared to be intact. The cellular arrangement and the proportion of different cell types within the epithelia was normal.     

卡马西平治疗前庭阵发症的疗效观察

目的 观察及评价卡马西平在前庭阵发症治疗中的临床疗效.方法 对2009年9月-2010年3月经眩晕门诊诊断的前庭阵发症患者20例,予以卡马西平进行干预后每月随访1次并进行疗效评价,共随访及评价3个月.结果 经随访观察,予以卡马西平干预后患者头晕的发作频率,发作程度较治疗前显著改善,且不良反应较轻,耐受性良好.结论 卡马西平治疗前庭阵发症有效且安全,值得临床推荐.     

Effects of the stimulus phase on the air-conducted ocular vestibular evoked myogenic potential in healthy subjects

Objective

The study aimed to examine the effect of the stimulus phase of air-conducted sound on ocular vestibular evoked myogenic potentials (oVEMPs).

Evidence against a hypothesis of vestibular efferent function

Efferent stimulation and nicotinic agonists can either decrease or increase the frequency of occurence of EPSPs recorded from VIIIth nerve afferents in the frog. It has been hypothesized that the distribution of hair cell resting membrane potentials overlaps the equilibrium potential dictated by the nicotinic-gated channels on the hair cells. Nicotinic mediated increases in EPSP frequency would then be due to depolarization of hair cells that were more hyperpolarized at rest, while decreases in EPSP frequency would be due to hyperpolarization of hair cells more depolarized ar rest. In order to test this hypothesis, while recording from afferents which showed an increase in EPSP frequency due to bath application of the nicotinic agonist DMPP (1,1-dimethyl-4-phenylpiperizinium iodide), hair cells were depolarized with 10 mM K⁺ in the bath, and then the effects of DMPP on EPSP frequency were assessed. In this situation, DMPP still increased EPSP frequency, suggesting that the equilibrium potential for the nicotinic-gated channel was much more positive than the resting potentials of the hair cells. An alternative hypothesis then seems likely, that the nicotinic receptors on hair cells are able to activate different iontophores that result in either hair cell depolarization or hyperpolarization, dependent upon which iontophore predominates in the hair cells innervating a particular afferent.