Journal of Vestibular Research - Volume 1, issue 2

Authors: Kimura, Robert S.

Article Type: Editorial

Abstract: Editor’s Note – At the 1990 Midwinter Meeting of the Association for Research in Otolaryngology, the Award of Merit of the Association was presented to Dr. Robert S. Kimura in recognition of his contributions to the field. During the introduction to his more formal comments, Dr. Kimura stressed the importance of team research, particularly the collaboration of clinicians and basic scientists. Dr. Kimura’s association with Dr. Schuknecht over the past two decades at Harvard Medical School serves as an exemplary model for such collaboration. Dr. Kimura’s comments come out of a mind which developed the best animal model in …existence for endolymphatic hydrops (in guinea pigs). Thus, one must carefully consider his words. Young investigators would do well to read carefully everything Dr. Kimura has written, and to spend as much time as possible with him. Dr. Kimura’s address to the Association follows. Show more

DOI: 10.3233/VES-1991-1201

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 107-108, 1991

Authors: Demer, Joseph L. | Goldberg, Jefim | Porter, Franklin I.

Article Type: Research Article

Abstract: Telescopic spectacles, highly magnifying visual aids mounted in spectacle frames, markedly alter the visual consequences of head movements. To evaluate the effect of this altered visual feedback on head stability, angular head velocity of normally sighted and low vision subjects was measured in the roll, pitch, and yaw axes. Measurements were made under two postural conditions: (1) quiet standing; and (2) walking in place, as well as three visual conditions: (1) eyes closed; (2) unmagnified vision; and (3) vision with 4× binocular telescopic spectacles. For normal subjects during quiet standing, both unmagnified vision and vision with telescopic spectacles tended …to reduce spontaneous head velocity in all axes as compared to the eyes-closed condition. However, in low vision subjects neither unmagnified vision nor vision with telescopic spectacles produced significant changes in values of head velocity relative to those measured with eyes closed. Spontaneous head velocities for standing low vision subjects tended to be higher than in normal subjects, although not all differences were statistically significant. During walking in place, Fourier analysis demonstrated prominent frequency components related to harmonics of the walking frequency under all viewing conditions. In normal subjects, vision with telescopic spectacles, to a greater degree than unmagnified vision, reduced head velocity during walking in the roll and yaw, but not the pitch, axes. For low vision subjects, significant reductions in head velocity during walking were observed only during vision with telescopic spectacles. These findings indicate that vision reduces angular instability of the head during standing and walking. Magnification produced by telescopic spectacles further improves head stability under some conditions, although the effect of vision is least evident in the pitch axis. The stabilizing effect of vision is reduced in low vision subjects. Show more

Keywords: head stability, low vision, telescopic spectacles, vision

DOI: 10.3233/VES-1991-1202

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 109-122, 1991

Authors: Ledin, T. | Ödkvist, L.M. | Vrethem, M. | Möller, C

Article Type: Research Article

Abstract: Twenty-eight patients with polyneuropathy aged 49–82 years (mean 67 years) were assessed by dynamic posturography. The patient group was compared to a control group comprising 29 healthy controls aged 70 through 75 years (mean 73 years). The dynamic posturography method comprises a sensory organization part in which the platform and visual surround are either stable or referenced to the patient’s sway; furthermore, the eyes are open or closed. In a movement coordination part the platform makes active movements. In the sensory organization part of the dynamic posturography the patient group showed significantly lower equilibrium performance compared to the control group …in the test conditions with absent vision, sway-referenced surrounding, and, finally, sway referenced platform and surrounding. In these conditions the influx of somatosensory information is of paramount importance for stable posture. In the movement coordination test, the patient group showed prolonged muscular response latencies in both forward and backward platform perturbations compared to the control group. It is concluded that dynamic posturography is a valuable diagnostic tool in assessment of the dynamic equilibrium performance in patients with polyneuropathy. Show more

Keywords: dynamic posturography, polyneuropathy, equilibrium

DOI: 10.3233/VES-1991-1203

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 123-128, 1991

Authors: Ledin, T. | Kronhed, A.C. | Mölier, C. | Mölier, M. | Ödkvist, L.M. | Olsson, B.

Article Type: Research Article

Abstract: All persons aged 70 through 75 years (N = 457) in a Swedish community were invited to participate in a 9 week balance training study. Out of 55 interested subjects, 15 were chosen at random for a study group; 15 matched controls were also selected. Before and after the investigation period the balance function was assessed by clinical balance tests and dynamic posturography. In the clinical balance tests, the training group significantly improved their balance standing on one leg with eyes closed as well as standing on one leg while shaking the head; they also walked 15 m back and …forth faster. In the dynamic posturography the training group significantly improved their equilibrium scores in the 3 most difficult test conditions. The results of the control group were unchanged except for one test condition in the dynamic posturography. The differences in one-leg standing with head shaking, walking 2 × 15 m, and the equilibrium score using sway-referenced platform in dynamic posturography were proved to be attributable to the training. The first investigation in all 29 subjects formed normative dynamic posturography data for the age group 70 through 75 years. The normative posturographic data of this age group differed from previously obtained data in the age groups 20 through 59 and 60 through 69 years. It is concluded that elderly may improve their balance by regular balance training exercises for as short a period as 9 weeks. This might prove to be of great value in improving balance and thereby preventing accidental falls and subsequent fractures in elderly. Show more

Keywords: dynamic posturography, training effects, aging, equilibrium

DOI: 10.3233/VES-1991-1204

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 129-138, 1991

Authors: Grant, J.W. | Cotton, J.R.

Article Type: Research Article

Abstract: The otolith organs were modeled mathematically as a 3-element system consisting of a viscous endolymph fluid in contact with a rigid otoconial layer that is attached to the skull by a gel layer. The gel layer was considered to be a viscoelastic solid, and was modeled as a simple Kelvin material. The governing differential equations of motion were derived and nondimensionalized, yielding 3 nondimensional parameters: nondimensional density, nondimensional viscosity, and nondimensional elasticity. The equations were solved using finite difference techniques on a digital computer. By comparing the model’s response with previous experimental research, values for the nondimensional parameters were found. …The results indicate that the inclusion of viscous and elastic effects in the gel layer are necessary for the model to produce otoconial layer deflections that are consistent with physiologic displacements. Future experimental data analysis and mathematical modeling effects should include viscoelastic gel layer effects, as this is a major contributor to system damping and response. Show more

Keywords: otolith, viscoelastic, gel layer, distributed parameter model, dynamic response

DOI: 10.3233/VES-1991-1205

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 139-151, 1991

Authors: Fox, Charles R. | Paige, Gary D.

Article Type: Research Article

Abstract: Effective interpretation of vestibular inputs to postural control requires that orientation of head on body is known. Postural stability might deteriorate when vestibular information and neck information are not properly coupled, as might occur with vestibular pathology. Postural sway was assessed in unilateral vestibulopathic patients before and acutely, 1,4, and 18+ months after unilateral vestibular ablation (UVA) as well as in normal subjects. Postural equilibrium with eyes closed was quantified as scaled pk-pk sway during 20 s trials in which the support surface was modulated proportionally with sway. Subjects were tested with the head upright and facing forward, turned 45∘ …right, and 45∘ left. Equilibrium was uninfluenced by head orientation in normal subjects. In contrast, patients after UV A showed both a general reduction in stability and a right/left head orientation-dependent asymmetry. These abnormalities adaptively recovered with time. It is concluded that vestibular inputs to postural control are interpreted within a sensory-motor context of head-on-body orientation. Show more

Keywords: posture, equilibrium, vestibular compensation

DOI: 10.3233/VES-1991-1206

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 153-160, 1991

Authors: Vercher, Jean-Louis | Gauthier, Gabriel M.

Article Type: Research Article

Abstract: To maintain clear vision, the images on the retina must remain reasonably stable. Head movements are generally dealt with successfully by counter-rotation of the eyes induced by the combined actions of the vestibulo-ocular reflex (VOR) and the optokinetic reflex. A problem of importance relates to the value of the so-called intrinsic gain of the VOR (VORG) in man, and how this gain is modulated to provide appropriate eye movements. We have studied these problems in two situations: 1. fixation of a stationary object of the visual space while the head moves; 2. fixation of an object moving with the head. …These two situations were compared to a basic condition in which no visual target was allowed in order to induce “pure” VOR. Eye movements were recorded in seated subjects during stationary sinusoidal and transient rotations around the vertical axis. Subjects were in total darkness (DARK condition) and involved in mental arithmetic. Alternatively, they were provided with a small foveal target, either fixed with respect to earth (earth-fixed target: EFT condition), or moving with them (chair-fixed-target: CFT condition). The stationary rotation experiment was used as baseline for the ensuing experiment and yielded control data in agreement with the literature. In all 3 visual conditions, typical responses to transient rotations were rigorously identical during the first 200 ms. They showed, sequentially, a 16-ms delay of the eye behind the head and a rapid increase in eye velocity during 75 to 80 ms, after which the average VORG was 0.9 ± 0.15. During the following 50 to 100 ms, the gain remained around 0.9 in all three conditions. Beyond 200 ms, the VORG remained around 0.9 in DARK and increased slowly towards 1 or decreased towards zero in the EFT and CFT conditions, respectively. The time-course of the later events suggests that visual tracking mechanisms came into play to reduce retinal slip through smooth pursuit, and position error through saccades. Our data also show that in total darkness VORG is set to 0.9 in man. Lower values reported in the literature essentially reflect predictive properties of the vestibulo-ocular mechanism, particularly evident when the input signal is a sinewave. Show more

Keywords: visuovestibular interaction, vestibulocular reflex, VOR suppression, smooth pursuit, human subjects

DOI: 10.3233/VES-1991-1207

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 161-170, 1991

Authors: Fukushima, Junko | Fukushima, Kikuro | Morita, Nobuyuki | Yamashita, Itaru

Article Type: Research Article

Abstract: Some schizophrenic patients have been known to have frontal cortical dysfunction. In view of the evidence that voluntary purposive eye movements and rapid head movements involve areas of the frontal cortex, investigations of saccade performance have been carried out on schizophrenics in various laboratories. We have compared performance of schizophrenic patients in tasks involving inhibition of reflexive saccades (no-saccade) and initiation of saccades without target (memory-saccade) with performance in. the antisaccade task. These measures were also compared with results of eye-head coordination tasks. Schizophrenics showed more errors and significantly longer latencies, with lower peak velocities at large amplitudes, in both …the anti saccade task and the memory-saccade task. Performance with coordinated eye-head movement was basically similar, except for significantly longer latencies of head movement. These results suggest that schizophrenics may have a disturbance in initiating and executing purposive saccades without targets, and that dysfunction of the frontal cortex may contribute to this disturbance. Show more

Keywords: saccade, antisaccade task, memory saccade task, schizophrenics, latency, error, peak velocity, eye-head coordination, CT scan, frontal cortical atrophy

DOI: 10.3233/VES-1991-1208

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 171-180, 1991

Authors: Hansen, H.C. | Gibson, J.M. | Zangemeister, W.H. | Kennardt, C.

Article Type: Research Article

Abstract: Eye-head movements to target steps of amplitude 3.75∘ to 30∘ were analyzed in 9 untreated patients with idiopathic Parkinson’s disease. Testing was performed before and after the introduction of a dopamimetic drug (L-dopa or bromocriptine) and compared with 9 normal controls. The patients showed a significantly greater scatter of mean head latencies prior to treatment, although their mean latencies were not significantly prolonged. When compared to controls, the patients’ head movements were of reduced peak velocity and gain. Treatment resulted in an improvement of gain but not velocity. Analysis of the frequency of gaze types showed no significant …effect of treatment. Show more

Keywords: eye/head coordination, L-dopa, saccades, basal ganglia, Parkinson’s disease

DOI: 10.3233/VES-1991-1209

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 181-186, 1991

Authors: Halmagyi, G.M. | Curthoys, I.S. | Cremer, P.D. | Henderson, C.J. | Staples, M.

Article Type: Research Article

Abstract: To determine the relative contributions of ampullofugal (AF) and ampullopetal (AP) stimulation of the horizontal semicircular canal (HSCC) to the horizontal vestibulo-ocular reflex (HVOR), 12 patients were studied 1 year after total unilateral vestibular deafferentation (UVD). Compensatory eye movement responses to impulses of horizontal head rotation were studied using magnetic search coils. The head impulses were rapid (up to 3000 deg/sec/sec) passive, unpredictable, step displacements of horizontal angular head position with respect to the trunk. Tbe results from these 12 patients were compared with results from 30 normal subjects. An HVOR deficit was found to each side. The HVOR in …response to head impulses toward the deafferented side, a response generated exclusively by ampullofugal stimulation of the single functioning HSCC, was severely deficient with an average gain of 0.25; the HVOR in response to head impulses toward the intact side, a response generated exclusively by ampullopetal stimulation of the single functioning HSCC, was mildly but significantly deficient compared with normal subjects. These results show that rapid, unpredictable head movements, unlike slow, predictable head movements, do demonstrate the AP-AF HVOR asymmetry, which could be expected from consideration of the behavior of single vestibular afferent neurons, an asymmetry that is expressed by Ewald’s 2nd Law. Show more

Keywords: vestibular, semicircular canal, oculomotor, labyrinth, vestibular compensation, VOR, vestibulo-ocular reflex, vestibular neurectomy

DOI: 10.3233/VES-1991-1210

Citation: Journal of Vestibular Research, vol. 1, no. 2, pp. 187-197, 1991