Journal of Vestibular Research - Volume 4, issue 6

Article Type: Other

DOI: 10.3233/VES-1994-4608

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. I-III, 1994

Article Type: Other

DOI: 10.3233/VES-1994-4609

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. VII-XII, 1994

Article Type: Other

DOI: 10.3233/VES-1994-4610

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. XIII-XIII, 1994

Article Type: Other

DOI: 10.3233/VES-1994-4611

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. XIV-XV, 1994

Authors: Morrison, Gavin | Hawken, Malcolm | Kennard, Christopher | Kenyon, Guy

Article Type: Research Article

Abstract: Fourteen patients in the latent phase of Menière's disease and 14 control subjects were tested on a moving platform apparatus as part of a protocol of investigations for Menière's disease. Subjects were tested under 3 different visual conditions (eyes open, eyes closed, sway feedback) and 2 proprioceptive conditions (fixed platform and ankle stabilization). There was a significant interaction between subject group and visual condition, Menière's patients bad a larger RMS sway amplitude than controls with their eyes open and closed, but this difference was abolished by sway feedback. Loss of either visual or proprioceptive sensory information increased sway amplitude, indicating …that both cues influence postural control, and in different ways, but patients were able to use these cues to maintain upright posture almost as effectively as controls. More patients than controls lost balance with ankles stabilized and eyes closed, but the difference was not statistically significant (P=0.0516). There was no detectable relationship between clinical ratings of disease severity and sway scores. The dynamic platform tests described in this report are more suitable for tests involving comparisons between groups of subjects rather than for diagnostic testing of individuals. Show more

Keywords: Menières disease, vision, proprioception, dynamic platform posturography

DOI: 10.3233/VES-1994-4601

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. 409-419, 1994

Authors: Furman, Joseph M. | Koizuka, Izumi

Article Type: Research Article

Abstract: Recent studies indicate that the direction of postrotatory nystagmus and optokinetic afternystagmus reorients toward earth-horizontal in tilted subjects. To further examine this phenomenon in humans, we studied 8 adults (4M, 4F) with no history of neurologic or otologic disease. Vestibular stimulation consisted of yaw off-vertical axis rotation (OVAR) trapezoids with eyes open in the dark at 60°/s constant velocity with a tilt angle of 30° and a deceleration at 100°/s2 to a stop in either the right-ear-down or the left-ear-down position. The optokinetic stimulus consisted of 5° wide black and white stripes projected against a cylindrical visual surround 1 …m in diameter rotated at a constant velocity of 30°/s. The projector, visual surround, and subject were all tilted by 30°; subjects were placed either in the right-ear-down or left-ear-down position. Eye position was measured using the magnetic scleral search coil technique. Each trial was scrutinized for the presence of reorientation of nystagmus in the subject's roll plane by looking for vertical nystagmus in the appropriate direction. Results indicated that reorientation of postrotatory nystagmus following OVAR was variable but often present. Reorientation of optokinetic afternystagmus was neither as consistent nor as robust as that seen following OVAR. These findings confirm that humans exhibit a predilection for eye rotations in the earth-horizontal plane. The presence of reorientation of postrotatory nystagmus (and to a lesser extent of optokinetic afternystagmus) suggests that static otolith inputs, which are known to alter velocity storage dynamics, also appear to alter the relative influence of velocity storage in different directions in humans. Show more

Keywords: vestibulo-ocular reflex, optokinetic nystagmus, velocity storage, cross-coupling

DOI: 10.3233/VES-1994-4602

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. 421-428, 1994

Authors: Kevetter, G.A. | Correia, M.J. | Martinez, P.R.

Article Type: Research Article

Abstract: The existence of separate subtypes of type I vestibular hair cells according to morphological criteria in situ was investigated. Gerbils were anesthetized and perfused with mixed aldehydes. The crista ampullaris of the posterior canal was dissected, fixed in osmium, dehydrated, and embedded in epon. Five-micron sections were cut orthogonal to the long axis of each crista. Measurements were made on camera lucida drawings of individual cells located in the apical, middle, and basal 1/3 of the crista. Measurements for each hair cell included the circumference, greatest width of the body, length, width of the apical surface (cuticular plate region, P), …width at narrowest portion of the neck (NW), neck width to plate ratio (NPR), length at a point 2 times NW from the apical surface (L2N). Type I hair cells were subgrouped into three classes (long -l, intermediate -i, and short -s) based on a subjective determination of neck length. Statistical comparisons were made between type I (n=612) and type II (n=74) hair cells and the type I subtypes (l, i, s). Statistically significant differences were found between type I and II hair cells for NPR, width, and length, but not perimeter. Thus, as in pigeons, NPR distinguishes type I and type II hair cells in the gerbil crista. While type I hair cells are wider and longer than type IIs, the circumference is the same, due to the restricted neck in type I hair cells. The L2N statistic separates three subtypes of type I hair cells. Finally, for type I hair cells, a statistically significant difference existed between the L2N statistic and each subregion of the crista. Show more

Keywords: vestibular, hair cells, labyrinth, semicircular canal

DOI: 10.3233/VES-1994-4603

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. 429-436, 1994

Authors: Li, Hongyan | Godfrey, Donald A. | Rubin, Allan M.

Article Type: Research Article

Abstract: The normal concentrations of 12 amino acids in the vestibular nuclei of rats were quantitatively measured using microdissection of freeze-dried brain sections combined with high performance liquid chromatography (HPLC) analysis. Doth excitatory amino acids, aspartate and glutamate, showed only small variation across the vestibular nuclei. The distribution of glutamine tended to parallel that of glutamate. The inhibitory amino acids, gamma-aminobutyrate (GABA) and glycine, were much more concentrated in some regions than in others. GABA tended to be more concentrated than glycine in dorsal and rostral nuclei, while glycine tended to be more concentrated than GABA in ventral and caudal nuclei. …The distribution of taurine was comparable to that of GABA, suggesting a close relationship with GABA function. Asparagine, serine, threonine, arginine, alanine and tyrosine had relatively low concentrations without significant differences among vestibular nuclei. Our results suggest that (1) different parts of the vestibular nuclear complex may receive similar amounts of excitatory amino acid afferents, (2) there is predominance of GABA or glycine as an inhibitory transmitter in different parts of the vestibular nuclear complex, and (3) there may be a close functional relationship between taurine and GABA within the vestibular nuclear complex. These results provide data basic to further research on the details of amino acid functions in the normal and abnormal vestibular system, as well as studies of plasticity in this system. Show more

Keywords: glutamate, GABA, taurine, glycine

DOI: 10.3233/VES-1994-4604

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. 437-452, 1994

Authors: Peng, G.C.Y. | Baker, J.F. | Peterson, B.W.

Article Type: Research Article

Abstract: Directional plasticity of the human vestibulo-ocular reflex (VOR) was studied in 10 subjects. The adaptation paradigm coupled 0.25 Hz, 19°/s vertical pitch vestibular rotations with 28°/s horizontal optokinetic oscillations. Electro-oculographic recordings in the dark were taken at 0.05, 0.1, 0.25, 0.5, and 1 Hz pitch rotations before and after training and at 15-minute intervals during 0.25 Hz adaptation. Peak head velocity was kept at 19°/sec for frequencies above 0.1 Hz, while constant amplitude was maintained at ±24° for 0.05 and 0.1 Hz. In all subjects, directional training produced slow phase horizontal VOR eye movements that were not present during vertical …rotations before adaptation. During the 2-hour training period, the cross-axis VOR gain at 0.25 Hz increased up to 0.16. Adaptive VOR gain was highest at the lowest frequency and reached a tuned peak at the 0.25 Hz training frequency. Cross-axis VOR phase remained around 0° at higher frequencies and lagged at lower frequencies. In all subjects, the cross-axis VOR gain was diminished when subjects were exposed to 0.25 Hz pitch rotations paired with a stationary visual field. The dynamics of the vertical VOR remained constant throughout the experiment. These results are further evidence that the frequency response characteristics of adaptive cross-axis VOR gain are similar in humans and cats, while phase behavior is less complex in humans. The high adaptive gain at low frequencies implicates otolith contributions during cross-axis adaptation. Show more

Keywords: vestibulo-ocular reflex, adaptation, vestibulo-ocular reflex plasticity, eye movements

DOI: 10.3233/VES-1994-4605

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. 453-460, 1994

Authors: Szturm, T. | Ireland, D.J. | Lessing-Turner, M.

Article Type: Research Article

Abstract: The purpose of this study was to evaluate the effects of two exercise programs on balance performance in patients with chronic peripheral vestibular dysfunction and to assess whether these exercise programs induce adaptive modifications of the vestibulo-ocular reflex (VOR). Patients were randomly assigned to one of two groups. (1) Those in the Rehab (Reh) group (n=11) received a comprehensive exercise program that consisted of balance retraining and goal-directed eye-head exercises under combinations of varied visual and somatosensory sensory conditions. Patients received 45-minute training sessions, three times per week for 12 weeks, and were instructed on a custom home exercise program. …(2) Those in the Home group (n=12) were instructed to perform the Cooksey-Cawthorne eye-head exercises at home, on a daily basis, for 12 weeks. In addition, after completion of the exercise program and a follow-up period, 7 of the participants in the Home group (here defined as the A group) chose to enter the Reh program (here defined as the B group). Balance performance was assessed by measuring the peak-to-peak magnitude and total amount of anterior-posterior body sway, and of horizontal (shear) ground reaction force during six test conditions, in which visual and somatosensory orientation cues were reduced or altered by rotation of the visual surround or support surface in proportion to the subject's sway, and in which vision was eliminated (eyes closed). The VOR response to step chair rotations of 60°/s and 120°/s, and the optokinetic reflex (OKN) response to 600/s constant velocity optokinetic stimuli were recorded. Left-right difference in VOR gain, VOR time constant, and OKN gain were determined. These tests were performed 1 day prior to start of treatment (TD 1), 6 weeks after start of treatment (TD 2), at the end of the 12-week treatment period (TD 3), and 5 months after end of treatment (TD 4). The findings revealed a significant improvement in standing balance performance under dynamic conditions for patients in the Reh program (Reh and B groups) but not for patients performing the eye-head exercise (Home or A groups). Thus, even inpatients with chronic vestibular dysfunction, compensation for the loss or disruption of peripheral vestibular inputs can be effectively induced by exercises that provide sensory feedback appropriate for behavioral changes involving sensory substitution or sensory-motor reorganization. In addition, a significant reduction in left-right differences in VOR gain was observed for the Reh group and B group (patients who performed exercises that involved eye and head movements where fixation on stationary and moving visual targets was a requirement), as compared to no change in the Home or A group (patients who performed eye and head oscillations where fixation was not a requirement). However, there was no significant change in left-right differences of the VOR time constant over the four test periods in any group. These results support the view that activities that produce error signals (ie, retinal image slip) that can be used to indicate the performance of the oculomotor system during head movements are required to facilitate recalibration of left-right differences in VOR gain. Show more

Keywords: vestibular disorders, rehabilitation, postural equilibrium, VOR, humans

DOI: 10.3233/VES-1994-4606

Citation: Journal of Vestibular Research, vol. 4, no. 6, pp. 461-479, 1994