Journal of Vestibular Research - Volume 15, issue 4

Authors: Zupan, Lionel H. | Merfeld, Daniel M.

Article Type: Research Article

Abstract: 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. Show more

Keywords: Human, graviceptors, ocular torsion, tilt perception, spatial orientation

DOI: 10.3233/VES-2005-15401

Citation: Journal of Vestibular Research, vol. 15, no. 4, pp. 173-183, 2005

Authors: Wright, W.G. | DiZio, P. | Lackner, J.R.

Article Type: Research Article

Abstract: We evaluated visual and vestibular contributions to vertical self motion perception by exposing subjects to various combinations of 0.2 Hz vertical linear oscillation and visual scene motion. The visual stimuli presented via a head-mounted display consisted of video recordings of the test chamber from the perspective of the subject seated in the oscillator. In the dark, subjects accurately reported the amplitude of vertical linear oscillation with only a slight tendency to underestimate it. In the absence of inertial motion, even low amplitude oscillatory visual motion induced the perception of vertical self-oscillation. When visual and vestibular stimulation were combined, self-motion perception …persisted in the presence of large visual-vestibular discordances. A dynamic visual input with magnitude discrepancies tended to dominate the resulting apparent self-motion, but vestibular effects were also evident. With visual and vestibular stimulation either spatially or temporally out-of-phase with one another, the input that dominated depended on their amplitudes. High amplitude visual scene motion was almost completely dominant for the levels tested. These findings are inconsistent with self-motion perception being determined by simple weighted summation of visual and vestibular inputs and constitute evidence against sensory conflict models. They indicate that when the presented visual scene is an accurate representation of the physical test environment, it dominates over vestibular inputs in determining apparent spatial position relative to external space. Show more

Keywords: Otoliths, self-motion perception, sensory integration, vertical linear oscillation, virtual environment

DOI: 10.3233/VES-2005-15402

Citation: Journal of Vestibular Research, vol. 15, no. 4, pp. 185-195, 2005

Authors: Ishiyama, Gail | Finn, Michael | Lopez, Ivan | Tang, Yong | Baloh, Robert W. | Ishiyama, Akira

Article Type: Research Article

Abstract: While most studies have demonstrated damage to the cochlear and vestibular endorgan as the primary site of aminoglycoside toxicity, the effect on the primary afferent neurons of the vestibular ganglion remains to be determined. This study used the unbiased stereology-optical fractionator method to obtain estimates of the vestibular ganglion neuronal number. Archival temporal bone specimens from seven subjects with a history of gentamicin (n = 3) and streptomycin (n = 4) aminoglycoside ototoxicity were used. The post-ototoxicity survival time ranged from two months to 8 years, with an average of 2.2 years. Seven archival human temporal bone specimens …from age-matched subjects with no history of audiovestibular symptoms or ototoxicity served as controls. Group means were compared using unpaired, two-tailed student's t test. The average vestibular ganglion neuronal number in the aminoglycoside ototoxicity group was 20, 733 neurons (CV = 0.073), which was significantly lower (p < 0.005) than the average number in the age-matched control group of 24, 902 neurons (CV = 0.109). These findings may be consistent with either retrograde degeneration or a direct neurotoxic effect of the aminoglycosides on the vestibular ganglion neuron. Show more

Keywords: Human temporal bone, archival human temporal bone, neuron number, unbiased stereology, vestibular ganglion, gentamicin, streptomyin, inner ear

DOI: 10.3233/VES-2005-15403

Citation: Journal of Vestibular Research, vol. 15, no. 4, pp. 197-202, 2005

Authors: Rajguru, Suhrud M. | Ifediba, Marytheresa A. | Rabbitt, Richard D.

Article Type: Research Article

Abstract: Horizontal canal (HC) benign paroxysmal positional vertigo (HC-BPPV) is a vestibular disorder characterized by bouts of horizontal ocular nystagmus induced during reorientation of the head relative to gravity. The present report addresses the application of a morphologically descriptive 3-canal biomechanical model of the human membranous labyrinth to study gravity-dependent semicircular canal responses during this condition. The model estimates dynamic cupular and endolymph displacements elicited during HC-BPPV provocative diagnostic maneuvers and canalith repositioning procedures (CRPs). The activation latencies in response to an HC-BPPV provocative diagnostic test were predicted to vary depending upon the initial location of the canalith debris (e.g. …within the HC lumen vs. in the ampulla). Results may explain why the onset latency of ocular nystagmus evoked by the Dix-Hallpike provocative maneuver for posterior canal BPPV are typically longer than the latencies evoked by analogous tests for HC-BPPV. The model was further applied to assess the efficacy of a 360°-rotation CRP for the treatment of canalithiasis HC-BPPV. Show more

Keywords: HC-BPPV, BPPV, BPV, Semicircular canal, vestibular disorder, vestibular mechanics, otoconia, vertigo, dizziness

DOI: 10.3233/VES-2005-15404

Citation: Journal of Vestibular Research, vol. 15, no. 4, pp. 203-214, 2005

Authors: Schmäl, Frank | Lübben, Björn | Weiberg, Kerstin | Stoll, Wolfgang

Article Type: Research Article

Abstract: Caloric testing of the vestibular labyrinth is usually performed by classical caloric test procedures (CCTP) using water warmed to 30°C and 44°C. Ice water irrigation (4°C) is usually not performed, although it might be useful as a bedside test. To verify the validity of the Minimal Ice Water Caloric Test (MIWCT), comparative video-oculographic investigations were performed in 22 healthy subjects using ice water (0.5 ml, 1.0 ml, 2 ml), CCTP, and cold air (27°C). Frequency, amplitude, slow phase velocity (SPV), the onset, and the duration of nystagmus were documented. After addition of three ice cubes, the temperature of conventional tap …water (16°C) fell within 13 min to 4°C. In pessimum position the subjects demonstrated no nystagmus response. Compared to CCTP, MIWCT was associated with a significantly later onset of nystagmus and a significant prolongation of the nystagmus reaction. In contrast to air stimulation (27°C), a significant Spearman's correlation was noted between MIWCT (1 and 2 ml) and established CCTP in respect of essential nystagmus parameters (frequency, amplitude and SPV). Furthermore, MIWCT (0.5 and 1 ml) showed a higher sensitivity and specificity with regard to the detection of canal paresis based on Jongkees' formula compared to stimulation with air 27°C. Thus, MIWCT appears to be a suitable procedure for bedside investigation of vestibular function outside the vestibular laboratory, e.g. in a hospital ward, where bedridden patients with vertigo occasionally require vestibular testing. Show more

Keywords: Vestibular examination, bedside test, lateral semicircular canal stimulation

DOI: 10.3233/VES-2005-15405

Citation: Journal of Vestibular Research, vol. 15, no. 4, pp. 215-224, 2005