Journal of Vestibular Research - Volume 6, issue 2

Article Type: Other

DOI: 10.3233/VES-1996-6210

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. I-II, 1996

Authors: Torte-Hoba, M.P. | Courjon, J.H. | Leroy, M.H. | Boyer, N. | Dominey, P. | Farhat, F. | Rebert, A.

Article Type: Research Article

Abstract: Acetylcholinesterase (AchE) activity was studied in pigmented rats 6 h to 1 y after hemilabyrinthectomy. A strong reduction of this activity was localized in the rostrocaudal extent of both he prepositus hypoglossi nucleus and the medial vestibular nucleus (that is, medial vestibular complex: VCm) ipsilateral to the lesion 6 h after the lesion. This deficit persisted within some areas dispersed throughout this complex 3 w and 1 y postoperatively. This result supports the hypothesis that the asymmetry of AchE activity in VCm could be necessary for vestibular compensation and provides an additional model for functional plasticity in the central nervous …system. Show more

Keywords: vestibular compensation, acetylcholinesterase activity, medial vestibular complex, pigmented rat, dynamic changes

DOI: 10.3233/VES-1996-6201

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 61-70, 1996

Authors: Jones, Sherri M. | Jones, Timothy A.

Article Type: Research Article

Abstract: Electrophysiological responses to pulsed linear acceleration stimuli were recorded in chicken embryos incubated for 19 or 20 days (E19/E20). Responses occurred within the first 16 ms following the stimulus onset. The evoked potentials disappeared following bilateral labyrinthectomy, but persisted following cochlear destruction alone, thus demonstrating that the responses were vestibular. Approximately 8 to 10 response peaks could be identified. The first 4 positive and corresponding negative components (early peaks with latencies < 6.0 ms) were scored and latencies and amplitudes quantified. Vestibular response latencies were significantly longer (P < 0.01) and amplitudes significantly smaller (P < 0.001) than those observed …in 2-week-old birds. Mean response threshold for anesthetized embryos was −15.9dBre 1.0 g/ms , which was significantly higher (P < 0.03) than those observed in 2-week-old birds (−23.0dBre 1.0 g/ms ). Latency/intensity functions (that is, slopes) were not significantly different between embryos and 2-week-old animals, but amplitude/intensity functions for embryos were significantly shallower than those for 2-week-old birds (P < 0.001). We presume that these differences reflect the refinement of sensory function that occurs following 19 to 20 days of incubation. The recording of vestibular evoked potentials provides an objective, direct and noninvasive measure of peripheral vestibular function in the embryo and, as such, the method shows promise as an investigative tool. The results of the present study form the definitive basis for using vestibular evoked potentials in the detailed study of avian vestibular ontogeny and factors that may influence it. Show more

Keywords: vestibular ontogeny, vestibular evoked potentials, linear acceleration, birds, linear jerk

DOI: 10.3233/VES-1996-6202

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 71-83, 1996

Authors: Nuti, O. | Passero, S. | Di Girolamo, S.

Article Type: Research Article

Abstract: Bilateral vestibular loss (BVL) is a relatively uncommon syndrome that may produce problems of balance; unsteady gait, especially in the dark; and visual disorders and/or oscillopsia associated with walking and head movements. Sometimes patients with BVL remain asymptomatic. Ototoxic drugs are the most frequently identified cause of BVL, but there are many other possible causes. The aetiology remains unknown in a large percentage of patients. In some, vascular aetiology may be suspected. Here we report 4 cases of vertebrobasilar dolichoectasia (VBD) and symptomatic BVL. In 3 subjects, hearing was preserved, but in the 4th, there was retrolabyrinthine hearing loss. In …our opinion, VBD may be the cause of BVL associated or not associated with hearing loss, the reason being that since the anterior vestibular artery is small and has no anastomoses, the horizontal semicircular canal is selectively susceptible to ischemia. Show more

Keywords: vertebrobasilar dolichoectasia, loss of vestibular function, labyrinthine artery

DOI: 10.3233/VES-1996-6203

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 85-91, 1996

Authors: Furman, Joseph M. | Mendoza, Juan Carlos

Article Type: Research Article

Abstract: The aim of this study was to further define the eye movement response to combined visual and vestibular stimulation, especially during linear acceleration. Subjects included 15 asymptomatic healthy individuals (8 females and 7 males) between the ages of 20 and 31 years. Vestibular stimulation consisted of earth-vertical axis rotation and off-vertical axis rotation (OVAR). Visual stimuli consisted of projected vertical stripes that were rotated for optokinetic trials and stationary for visual augmentation trials. A small laser target (0.5 mW, 0.50° arc) that rotated with the subject was used for fixation trials. Eye movements were measured with electro-oculography. Results showed that …visual-vestibular interaction during sinusoidal rotation was not affected by a 15° off-vertical tilt. Constant velocity OVAR induced a continuous nystagmus whose slow component velocity contained a nonzero baseline, that is, a bias, and a periodic fluctuation at the rotation frequency, that is, a modulation component. The modulation component during visual fixation was reduced as compared with that seen during rotation in the dark, but was not absent. Constant velocity OVAR in the presence of earth-fixed stripes induced a consistent sinusoidal modulation. Our results suggest that visual-vestibular interaction for otolith stimulation differs from visual-vestibular interaction for semicircular canal stimulation. The modulation component of the response to OVAR appears to be modified by visual stimulation to a lesser extent than other vestibular-induced eye movements and thus may reflect a more “direct” vestibulo-ocular response. The bias component of the response to OVAR can be substantially influenced by vision and thus may depend upon more “indirect” pathways. Show more

Keywords: vestibulo-ocular reflex, otolith, human

DOI: 10.3233/VES-1996-6204

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 93-103, 1996

Authors: Cortopassi, K.A. | Lewis, E.R.

Article Type: Research Article

Abstract: A common property of vertebrate acoustic sensors, including otoconial acoustic sensors in lower vertebrates, is steep slopes on the high- and low-frequency band edges of the amplitude tuning curves. Bullfrog otoconial acoustic fibers are responsive to sound and exquisitely responsive to substrate vibrations in the frequency range from 20 Hz to 300 Hz. The sum of the absolute values of the two band-edge slopes of the amplitude tuning curve of such a fiber typically ranges from 100 dB/decade to 160 dB/decade (sometimes as high as 220 dB/decade), implying typical dynamic order of at least five to eight. We wondered if …such steep slopes and the high dynamic order implied by them reflect special adaptations in acoustic sensors or if they are inherent in all lower-vertebrate otoconial sensors excited in this frequency range. To address this question, we examined the amplitude tuning characteristics of afferent nerve fibers from a bullfrog otoconial vestibular sensor in the same frequency range. In this paper, we report observations of tuning for bullfrog lagenar vestibular fibers in the frequency range from 10 Hz to approximately 500 Hz. To make these observations, we stimulated the frog with random dorsoventral motion that exhibited Gaussian amplitude distribution and that was flat in velocity from 10 Hz to 1.0 kHz. For each afferent fiber studied, we used discrete cross-correlation (between stimulus waveform and axon spike train) and discrete Fourier transformation to compute an amplitude tuning curve. In contrast with the amplitude tuning curves from saccular and lagenar acoustic fibers, those from the lagenar vestibular fibers typically had band-edge slopes whose absolute values summed to approximately 20 dB/decade, implying typical dynamic order of one. We conclude that steep band-edge slopes and high dynamic order are indeed special features of acoustic sensors, not shared by vestibular sensors. Show more

Keywords: vestibular amplitude tuning curves, low- and high-frequency slopes, dynamic order, frog lagena

DOI: 10.3233/VES-1996-6205

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 105-119, 1996

Authors: Suzuki, Mamoru | Kadir, Abdul | Hayashi, Naoki | Takamoto, Muneo

Article Type: Research Article

Abstract: Bull frogs posterior semicircular canals (psc) were used to simulate the condition of benign paroxysmal positional vertigo (BPPV). The psc was isolated in frog Ringer's solution, and the saccular otoconia were used as a responsible material to stimulate the cupula. When the otoconia were placed on the cupular surface to mimic the condition of cupulolithiasis, the psc ampullary nerve action potentials instantaneously changed according to the direction of the gravity produced by otoconia. When the otoconia were dropped into the canal to mimic the condition of moving otoconia in the canal, the action potentials changed together with the otoconial flow …after a latent period. Both cupulolithiasis and moving otoconia are possibly valid mechanisms of BPPV, since they effectively stimulate the cupula. However, moving otoconia with a latent period would better explain clinical features of BPPV. Show more

Keywords: mechanism, benign paroxysmal positional vertigo, otoconia

DOI: 10.3233/VES-1996-6206

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 121-125, 1996

Authors: Takeda, N. | Hashikawa, K. | Moriwaki, H. | Oku, N. | Koizuka, I. | Kitahara, T. | Taya, N. | Kubo, T. | Nishimura, T.

Article Type: Research Article

Abstract: The effects of caloric vestibular stimulation on regional cerebral blood flow (rCBF) of the parietal and temporal cortex were examined in 10 healthy volunteers. The consecutive 99m Te-hexa-methyl-propyleneamine oxime (99m Tc-HMPAO) single-photon emission computed tomography (SPECT) method with region of interest analysis was used. Changes in rCBF induced by caloric stimulation with cold air (25°C) were evaluated in comparison with those induced by control stimulation with air at body temperature (37°C). Caloric stimulation with cold air induced vertigo in 4 subjects, dizziness in 2, and no sensation of self-motion in the remaining 4 subjects, whereas, control stimulation did not induce …the sensation of self-motion in any subject. Although both parietal and temporal rCBF were slightly decreased during caloric stimulation, a correlation could be established between the magnitude of left-right differences in change of parietal rCBF and the degree of self-motion perception induced by cold-air caloric stimulation, as compared to control stimulation. Left-right differences in change of parietal rCBF in subjects with vertigo during caloric stimulation were significantly higher than those in subjects without any sensation of self-motion. In contrast, there was no correlation between the magnitude of left-right difference in change of parietal rCBF and maximum slow phase eye velocity induced by caloric stimulation. These findings suggest that the parietal lobe is involved in the perception of vertigo due to vestibular stimulation, but not in the vestibulo-ocular reflex. Show more

Keywords: vestibular cortex, vertigo, caloric stimulation, single-photon emission computed tomography

DOI: 10.3233/VES-1996-6207

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 127-134, 1996

Authors: Martin, Jacelyn | Gilchrist, Darrin P.D. | Smith, Paul F. | Darlington, Cynthia L.

Article Type: Short Communication

Abstract: Diazepam and other benzodiazepines are sometimes used to alleviate vertigo and dizziness following labyrinthine surgery in humans. While the results of some previous studies have suggested that the administration of diazepam and other CNS depressant drugs following unilateral labyrinthectomy (UL) may impair the vestibular compensation process, the available evidence is unclear. The objective of the present experiment was to examine the effects of multiple injections of a high dose of diazepam (that is, 10 mg/kg ip) 30 min before and following UL (10 h or 10 and 20 h) on the static symptom, spontaneous ocular nystagmus (SN), in guinea pigs. …Although diazepam-treated animals exhibited consistently lower average SN frequency compared to vehicle controls, neither SN frequency nor its rate of compensation were significantly different between the 2 groups. The time to complete SN compensation was also similar for the 2 groups, as estimated from the x intercepts derived from a linear regression analysis. These results suggest that even high doses of diazepam before and following UL do not result in an impairment of compensation of SN in guinea pig. Show more

Keywords: unilateral labyrinthectomy, vestibular compensation, diazepam, benzodiazepines

DOI: 10.3233/VES-1996-6208

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 135-139, 1996

Authors: Hawken, Malcolm

Article Type: Book Review

DOI: 10.3233/VES-1996-6209

Citation: Journal of Vestibular Research, vol. 6, no. 2, pp. 141-143, 1996