Journal of Vestibular Research - Volume 12, issue 1

Authors: Sun, Yizhe | Godfrey, Donald A. | Rubin, Allan M.

Article Type: Research Article

Abstract: Extracellular single unit recordings were made from regularly discharging medial vestibular nucleus neurons in brain slices from control rats and from rats surviving 7 days after bilateral transection of the inferior cerebellar peduncle. Decreases in firing rate during perfusion with the Îş-aminobutyric acid (GABA) agonists, muscimol (GABA A ) and baclofen (GABA B ), were greater in lesioned rats than in control rats. For the grouped data, the half-maximally-effective concentrations of muscimol and baclofen were 3.2 µM, as compared with 19.6 µM for control, and 0.8 µM, as compared with 2.7 µM …for control, respectively. The antagonists bicuculline (GABA A ) and 2-OH-saclofen (GABA B ) only minimally affected the spontaneous firing rates of neurons in lesioned rats, significantly less than in control rats. The data suggest that the decreases of endogenous GABA levels in the medial vestibular nucleus after inferior cerebellar peduncle transection are accompanied by up-regulation of GABA A and, to a lesser extent, GABA B receptors. Show more

Keywords: GABAA receptor, GABAB receptor, Muscimol, Baclofen, Bicuculline, 2-OH-saclofen

DOI: 10.3233/VES-2002-12101

Citation: Journal of Vestibular Research, vol. 12, no. 1, pp. 1-14, 2002

Authors: Yasuda, Keiko | Fushiki, Hiroaki | Wada, Rinnosuke | Watanabe, Yukio

Article Type: Research Article

Abstract: While the stimulation of otolith inputs reduces the duration of postrotatory nystagmus (PRN), there is still room for dialogue about the effect of static tilt on the orientation of PRN. We studied one possible influence of static roll tilt on the spatial orientation of PRN in cats. The animal was rotated about an earth-vertical axis (EVA) at a constant velocity of 100 deg/s with an acceleration and deceleration of 120 deg / s 2 . Within two seconds after stopping EVA rotation, the animal was passively tilted at 45 deg/s about its longitudinal axis by …as much as ± 90 deg in steps of 15 deg. Eye movements were measured with magnetic search coils. The angle of the PRN plane and its slow phase eye velocity were measured. The time constant of PRN decreased with an increase in roll tilt. The PRN plane remained earth horizontal within a range of ± 30  deg roll tilt. Beyond this range, the velocity of PRN decreased too rapidly to measure any change in orientation. Our results indicate a spatially limited and temporally short interaction of the semicircular canal and otolith signals in the velocity storage mechanism of cat PRN. Our data, along with previous studies, suggest that different species show different solutions to the problem of the imbalance and spatial disorientation during contradictory stimuli. Show more

Keywords: VOR, vestibular dumping, semicircular canal-otolith interaction, velocity storage mechanism

DOI: 10.3233/VES-2002-12102

Citation: Journal of Vestibular Research, vol. 12, no. 1, pp. 15-23, 2002

Authors: Chen, K.J. | Keshner, E.A. | Peterson, B.W. | Hain, T.C.

Article Type: Research Article

Abstract: Control of the head involves somatosensory, vestibular, and visual feedback. The dynamics of these three feedback systems must be identified in order to gain a greater understanding of the head control system. We have completed one step in the development of a head control model by identifying the dynamics of the visual feedback system. A mathematical model of human head tracking of visual targets in the horizontal plane was fit to experimental data from seven subjects performing a visual head tracking task. The model incorporates components based on the underlying physiology of the head control system. Using optimization methods, we …were able to identify neural processing delay, visual control gain, and neck viscosity parameters in each experimental subject. Show more

Keywords: mathematical model, head control, vision, gaze

DOI: 10.3233/VES-2002-12103

Citation: Journal of Vestibular Research, vol. 12, no. 1, pp. 25-33, 2002

Authors: Brantberg, Krister | Tribukait, Arne

Article Type: Research Article

Abstract: 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. Show more

Keywords: VEMP, skull taps, sacculus, utriculus, vestibulocollic

DOI: 10.3233/VES-2002-12104

Citation: Journal of Vestibular Research, vol. 12, no. 1, pp. 35-45, 2002

Authors: Cohen, Helen S. | Kimball, Kay T.

Article Type: Research Article

Abstract: Fifty-three subjects with peripheral, chronic vestibulopathies, who were referred for vestibular rehabilitation, were tested on a path integration task before and after doing four weeks of five times daily habituation exercises for vertigo reduction. The task involved walking over a 7.62 m path with eyes closed. Dependent measures were velocity and angle of veering from the straight ahead. At the post-test and at succeeding follow-up tests for up to six months, subjects had significant increases in velocity and significant declines in angle of veering. Length of time subjects had vertigo prior to starting rehabilitation, and speed of head movement exercises …were not associated with improvements. These data support the previous finding that patients with vestibular impairments have decreased performance on this task. The data also suggest that vestibular rehabilitation, given as a simple home program, is associated with improvements in this skill. Show more

DOI: 10.3233/VES-2002-12105

Citation: Journal of Vestibular Research, vol. 12, no. 1, pp. 47-51, 2002

Authors: Ahmad, Saad | Rohrbaugh, John W. | Anokhin, Andrey P. | Sirevaag, Erik J. | Goebel, Joel A.

Article Type: Research Article

Abstract: The relationship between lifetime alcohol consumption and postural control was investigated in 35 subjects with no clinically-detectable neurologic abnormalities, using computerized dynamic posturography (CDP) procedures. The estimated total number of lifetime alcoholic drinks was positively correlated with anteroposterior sway spectral power within the 2–4 Hz and 4–6 Hz frequency bands, in three Sensory Organization Test (SOT) conditions: eyes closed with stable support surface (SOT 2), eyes open with sway-referenced support (SOT 4), and eyes closed with sway-referenced support (SOT 5). All correlations remained significant after controlling for subject age, and were increased after excluding nine drug-abusing subjects. In contrast to …the strong findings for frequency-based measures, no correlation was observed using conventional amplitude-based sway measures. These results suggest that 1) alcohol consumption compromises postural control in an exposure-dependent manner, and 2) sway frequency analysis reveals pathological processes not manifested in conventional CDP measures of sway amplitude. Show more

DOI: 10.3233/VES-2002-12106

Citation: Journal of Vestibular Research, vol. 12, no. 1, pp. 53-64, 2002