Journal of Vestibular Research - Volume 16, issue 1-2

Authors: Fukushima, Junko | Akao, Teppei | Kurkin, Sergei | Kaneko, Chris R.S. | Fukushima, Kikuro

Article Type: Research Article

Abstract: In order to see clearly when a target is moving slowly, primates with high acuity foveae use smooth-pursuit and vergence eye movements. The former rotates both eyes in the same direction to track target motion in frontal planes, while the latter rotates left and right eyes in opposite directions to track target motion in depth. Together, these two systems pursue targets precisely and maintain their images on the foveae of both eyes. During head movements, both systems must interact with the vestibular system to minimize slip of the retinal images. The primate frontal cortex contains two pursuit-related areas; the caudal …part of the frontal eye fields (FEF) and supplementary eye fields (SEF). Evoked potential studies have demonstrated vestibular projections to both areas and pursuit neurons in both areas respond to vestibular stimulation. The majority of FEF pursuit neurons code parameters of pursuit such as pursuit and vergence eye velocity, gaze velocity, and retinal image motion for target velocity in frontal and depth planes. Moreover, vestibular inputs contribute to the predictive pursuit responses of FEF neurons. In contrast, the majority of SEF pursuit neurons do not code pursuit metrics and many SEF neurons are reported to be active in more complex tasks. These results suggest that FEF- and SEF-pursuit neurons are involved in different aspects of vestibular-pursuit interactions and that eye velocity coding of SEF pursuit neurons is specialized for the task condition. Show more

Keywords: Smooth pursuit, vergence, gaze velocity, vestibulo-ocular reflex, semi-circular canal, otolith, frontal eye fields, supplementary eye fields

DOI: 10.3233/VES-2006-161-201

Citation: Journal of Vestibular Research, vol. 16, no. 1-2, pp. 1-22, 2006

Authors: Wright, W. Geoffrey | DiZio, Paul | Lackner, James R.

Article Type: Research Article

Abstract: We evaluated the influence of moving visual scenes and knowledge of spatial and physical context on visually induced self-motion perception in an immersive virtual environment. A sinusoidal, vertically oscillating visual stimulus induced perceptions of self-motion that matched changes in visual acceleration. Subjects reported peaks of perceived self-motion in synchrony with peaks of visual acceleration and opposite in direction to visual scene motion. Spatial context was manipulated by testing subjects in the environment that matched the room in the visual scene or by testing them in a separate chamber. Physical context was manipulated by testing the subject while seated in a …stable, earth-fixed desk chair or in an apparatus capable of large linear motions, however, in both conditions no actual motion occurred. The compellingness of perceived self-motion was increased significantly when the spatial context matched the visual input and actual body displacement was possible, however, the latency and amplitude of perceived self-motion were unaffected by the spatial or physical context. We propose that two dissociable processes are involved in self-motion perception: one process, primarily driven by visual input, affects vection latency and path integration, the other process, receiving cognitive input, drives the compellingness of perceived self-motion. Show more

Keywords: Self-motion perception, virtual environment, sensory integration

DOI: 10.3233/VES-2006-161-202

Citation: Journal of Vestibular Research, vol. 16, no. 1-2, pp. 23-28, 2006

Authors: Gottshall, Kim R. | Hoffer, Michael E. | Cohen, Helen S. | Moore, Robert J.

Article Type: Research Article

Abstract: Study design: Four groups, between-subjects study. Objectives: To investigate the effects of exercise on adaptation of normal subjects who had been artificially spatially disoriented. Background: Many patients referred for rehabilitation experience sensory changes, due to age or disease processes, and these changes affect motor skill. The best way to train patients to adapt to these changes and to improve their sensorimotor skills is unclear. Using normal subjects, we tested the hypothesis that active, planned head movement is needed to adapt to modified visual input. Methods and measures: Eighty male and female subjects …who had normal balance on computerized dynamic posturography (CDP) and the dynamic gait index (DGI), were randomly assigned to four groups. All groups donned diagonally shift lenses and were again assessed with CDP and DGI. The four groups were then treated for 20 min. Group 1 (control group) viewed a video, Group 2 performed exercise that involved translating the entire body through space, but without separate, volitional head movement, Group 3 performed exercises which all incorporated volitional, planned head rotations, and Group 4 performed exercises that involved translating the body (as in Group 2) and incorporated volitional, planned head motion (as in Group 3). All subjects were post-tested with CDP and DGI, lenses were removed, and subjects were retested again with CDP and DGI. Results: The groups did not differ significantly on CDP scores but Groups 3 and 4 had significantly better DGI scores than Groups 1 and 2. Conclusions: Active head movement that is specifically planned as part of the exercise is more effective than passive attention or head movements that are not consciously planned, for adapting to sensorimotor change when it incorporates active use of the changed sensory modality, in this case head motion. Show more

DOI: 10.3233/VES-2006-161-203

Citation: Journal of Vestibular Research, vol. 16, no. 1-2, pp. 29-33, 2006

Authors: Tribukait, Arne

Article Type: Research Article

Abstract: The subjective visual horizontal (SVH) was measured in the upright position and at 10, 20, and 30 degrees of head and body tilt to the right and left. Normal subjects (n=25) were tested on two separate occasions with an interval of 1–14 days. Test variables considered were the SVH in the upright position, the perception of tilt to the right and left, calculated on the basis of the SVH in the upright and tilted positions, and the asymmetry in tilt perception. There was no correlation between the perception of tilt to the right and to the left r=0.10). Neither was …there any correlation between the SVH in the upright position, representing a resting asymmetry, and the asymmetry in tilt perception, i.e. the response asymmetry (r=0.17). However, for each variable, there was a high correspondence between data obtained at test and retest (r ranged from 0.68 to 0.89, p<0.001), suggesting that the independence between variables is not due to noise. Findings are discussed taking into consideration the possible roles of otoliths and semicircular canals in the formation of the SVH. In an attempt to explain the independence between the two measures of asymmetry it is hypothesized that while the otoliths must be essential for the perception of static lateral tilt, the SVH in the upright position to a considerable degree reflects semicircular canal function. Show more

Keywords: Vestibular, labyrinth, otolith, utricle, semicircular canal

DOI: 10.3233/VES-2006-161-204

Citation: Journal of Vestibular Research, vol. 16, no. 1-2, pp. 35-43, 2006

Authors: Peterka, Robert J. | Wall III, Conrad | Kentala, Erna

Article Type: Research Article

Abstract: We present a quantitative method for characterizing the effectiveness of a balance prosthesis based on tactile vibrators. The balance prosthesis used an array of 12 tactile vibrators (tactors) placed on the anterior and posterior surfaces of the torso to provide body orientation feedback related to the angular position and velocity of anterior-posterior body sway. Body sway was evoked in subjects with normal sensory function and in vestibular loss subjects by rotating the support surface upon which a test subject stood with eyes closed. Tests were performed both with (tactor trials) and without (control trials) the prosthesis activated. Several amplitudes of …support surface stimulation were presented with each stimulus following a pseudorandom motion profile. For each stimulus amplitude, a transfer function analysis characterized the amplitude (gain) and timing (phase) of body sway evoked by the support surface stimulus over a frequency range of 0.017 to 2.2 Hz. A comparison of transfer function results from the control trials of normal subjects with results from tactor trials of vestibular loss subjects provided a quantitative measure of the effectiveness of the balance prosthesis in substituting for missing vestibular information. Although this method was illustrated using a specific balance prosthesis, the method is general and could be applied to balance prostheses that utilize other technology. Show more

Keywords: Vestibular, balance prosthesis, posture, orientation, vibrotactile, human

DOI: 10.3233/VES-2006-161-205

Citation: Journal of Vestibular Research, vol. 16, no. 1-2, pp. 45-56, 2006

Authors: King, John E. | González, Jorge E. | Fuller, Michael I.

Article Type: Research Article

Abstract: The purpose of this study was to design an automated mental alerting task that could be utilized when performing vestibular testing on a broad range of patient populations, including certain difficult-to-test populations, such as the hard-of-hearing. A device was developed that utilized vibrotactile stimuli output to two vibrators placed on the subject's left leg, and responded to activation of two momentary pushbuttons controlled by the subjects. Fourteen normal-hearing subjects without history or symptoms of vestibular involvement participated. Each participant underwent three mental-alerting conditions, defined as no task, verbal task, or vibrotactile task. Each condition involved four irrigations of …the ear canals, two with warm water and two with cool water. The resultant nystagmus was recorded and analyzed using four measures to compare the effect of the mental alerting task condition. No significant difference was found between verbal and vibrotactile alerting both of which provided better responses than the no alerting task (F=8.443; df=2,13; p=0.001). Between-subjects analysis showed that the number of gaps, which are undesirable periods of absent nystagmus during test recordings, was smallest for the verbal and vibrotactile tasks, and largest for the no task condition. Overall, the results showed that the vibrotactile tasking device (VTD) is an effective alternative means of providing mental alerting during vestibular testing, specifically that of caloric examination. Show more

Keywords: Vestibular testing, mental alerting, nystagmus, suppression

DOI: 10.3233/VES-2006-161-206

Citation: Journal of Vestibular Research, vol. 16, no. 1-2, pp. 57-67, 2006

Authors: Takai, Yoshinari | Murofushi, Toshihisa | Ushio, Munetaka | Iwasaki, Shinichi

Article Type: Research Article

Abstract: The time course of the recovery of subjective visual horizontal (SVH) after unilateral vestibular deafferentation by intratympanic instillation of gentamicin was studied. Six patients who underwent intratympanic gentamicin instillation therapy for Meniere's disease (1 man and 5 women, 32 to 69 years of age) were enrolled in this study. For comparison, SVH in 23 healthy subjects (12 men and 11 woman, 23 to 48 years of age) was also measured. The mean ± SD of SVH in healthy subjects was 0.0 ± 1.1 deg. All of the 6 patients showed significantly deviated SVH toward the injected side-down at the early …stage after the therapy. Although one patient showed recovery of SVH to the normal range 25 days after the injection, the other patients required more time for recovery. Three patients did not show recovery to the normal range after 1 year. On the other hand, spontaneous nystagmus observed using an infrared CCD camera in total dark disappeared after 35 days (median). Patients who had normal vestibular evoked myogenic potentials before the therapy showed a tendency of delay of recovery of SVH. The reasons why the recovery of SVH took longer than the disappearance of spontaneous nystagmus are discussed in this report. Show more

Keywords: Subjective visual vertical, utricle, otolith organ, vestibular compensation, Meniere's disease

DOI: 10.3233/VES-2006-161-207

Citation: Journal of Vestibular Research, vol. 16, no. 1-2, pp. 69-73, 2006