Journal of Vestibular Research - Volume 9, issue 2

Authors: Ris, Laurence | Saussez, Sven | Gerrits, Nicolaas | Godaux, Emile | Pochet, Roland

Article Type: Research Article

Abstract: A detailed map of the vestibular nuclear complex of the guinea pig has been established by Gstoettner and Burian (1987), using cytoarchitectonic (cresyl violet staining) and fiberarchitectonic criteria. However, the exact borders between the different subdivisions are not always evident in Nissl stained sections. In the present study, serial sections of the vestibular nuclei of the guinea pig were stained to visualize acetylcholinesterase (AChE) activity, and compared with corresponding sections stained with cresyl violet. All of the subdivisions of the vestibular nuclear complex previously described are more readily distinguished in AChE than in Nissl preparations. The AChE reactivity also shows …that the medial vestibular nucleus extends more rostrally than previously described. Furthermore, it questions whether the area classically referred to as the rostral pole of the descending vestibular nucleus belongs to the descending vestibular nucleus or to the lateral vestibular nucleus (LV). Finally, a morphometric analysis performed on cresyl violet stained sections shows that (1) in the caudal LV, the neurons of the ventromedial extension are smaller than those of the dorsolateral extension and that (2) in the rostral LV, the ventromedial division contains a larger ratio of smaller neurons than the dorsolateral one. Show more

Keywords: vestibular nuclei, acetylcholinesterase, histochemistry, guinea pig

DOI: 10.3233/VES-1999-9201

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 73-81, 1999

Authors: Johnson, Walter H. | Sunahara, Fred A. | Landolt, Jack P.

Article Type: Research Article

Abstract: The objective of this study was to determine the importance, if any, of the non-auditory labyrinth of the inner ear in visually induced nausea and self-vection in subjects exposed to a moving visual field with and without concomitant pitching head movements. Subjects teated were 15 normals, 18 unilateral labyrinthectomies and 6 bilateral labyrinthectomies. The findings show a higher incidence of pseudo-Coriolis induced nausea in normal subjects compared to unilateral and bilateral labyrinthectomized subjects. When the subjects were exposed to the moving visual field only (no head movement), pronounced self-vection occurred in all subjects, but with earlier onset in the bilateral …labyrinthine defective subjects as compared to normal and unilateral defective subjects. The subjective intensities of self-vections reported by labyrinth-defectives were much more pronounced as compared to normal subjects, and it is apparent that visual input in these subjects achieves much more importance in maintaining compensatory eye movements, and the gain of neck reflexes is enhanced. The findings that visual stimulation is more effective in producing the disabling effects after labyrinthine destruction could possibly be explained by enhancement of vision after loss of labyrinthine sensory input, and the gain in neck reflexes is also enhanced after labyrinthectomy. Show more

DOI: 10.3233/VES-1999-9202

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 83-87, 1999

Authors: Bouyer, L.J.G. | Watt, D.G.D.

Article Type: Research Article

Abstract: Acute, reversible changes in human vestibular function can be produced by exposure to “Torso Rotation” (TR), a method involving the overuse of certain types of simple, self-generated movements. A single session results in multiple, short-lasting aftereffects, including perceptual illusions, VOR gain reduction,gaze and postural instability, and motion sickness. With repeated exposure, motion sickness susceptibility disappears and gaze stability improves. VOR gain continues to be reduced, however. Therefore, another gaze stabilizing system must come into play. Are visual and/or neck inputs involved in this functional compensation? Six subjects participated in this 7-day experiment. Eye and head movements were measured during 2 …tests: 1) voluntary “head only” shaking between 0.3 and 3.0 Hz (lights off) and 2) voluntary “head and torso” shaking, moving the upper body en bloc (neck immobilized). Measurements were obtained before and repeatedly after TR. Velocity gain (eye velocity/head velocity) was determined for each of these tests. Each day, mean velocity gain during “head only” shaking in the dark (averaged over 1.0 to 2.0 Hz) dropped significantly after TR (P < 0.01 ), with no long-term improvement (P > 0.9 ). Similar results, although more noisy, were obtained for “head and torso” shaking. As a control, EOG calibration data confirmed that gaze stability in the light did improve over the 7 days of testing. This experiment demonstrates that the reduction in gaze instability following repeated exposure to TR results from an increased use of vision. It excludes the VOR, the COR, and predictive mechanisms (including efference copy) as contributors. In addition, in the 20 minutes following TR completion, gaze stability recovered less than during previous VOR testing in the dark. These results are compatible with the motion that exposure to TR leads to a change in sensorimotor strategy involving a de-emphasis of vestibular inputs. Show more

Keywords: vestibulo-ocular, cervico-ocular, vision, functional compensation

DOI: 10.3233/VES-1999-9203

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 89-101, 1999

Authors: Reginella, Reginald L. | Redfern, Mark S. | Furman, Joseph M.

Article Type: Research Article

Abstract: Sensory information from lightly touching a reference with the hand is known to influence postural sway in young adults. The primary aim of this study was to compare the influence of finger contact (FC) with an earth-fixed reference to the influence of FC with a body-fixed reference. A second goal of this study was to determine if FC is used differently by older adults compared to younger adults. Using a force plate, center of pressure at the feet was recorded from blindfolded young and older subjects during several conditions. Subjects either did or did not lightly touch a force-sensitive plate …that was either earth-fixed or moved forward and backward in synchrony with body sway (that is, sway-referenced). In addition, support surface conditions were also varied, including a fixed floor and a sway-referenced floor using an EquitestTM . Results showed that the type of FC, floor condition, and age each had an effect on postural sway. Touching an earth-fixed plate decreased postural sway as compared to no touching, while touching a sway-referenced plate incresased sway. This influence of FC was enhanced when the floor was sway-referenced. Although older subjects swayed more than young subjects overall, no age-FC interactions occurred, indicating that FC was not utilized differently between the age groups. This study suggests that FC cannot be disregarded as erroneous, especially when proprioceptive information from the legs is distorted. Further, FC is integrated with other sensory information by the postural control system similarly in young and older persons. Show more

Keywords: posture, contact, sway, Equitest, proprioception

DOI: 10.3233/VES-1999-9204

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 103-109, 1999

Authors: Schlatter, Melanie | Kerr, DeWana R. | Smith, Paul F. | Darlington, Cynthia L.

Article Type: Research Article

Abstract: The concentrated Ginkgo biloba extract, EGb 761, has previously been reported to enhance and accelerate vestibular compensation following unilateral vestibular deafferentation (UVD), in particular, compensation of the dynamic postural symptoms such as locomotor dysequilibrium. However, many of these studies have not included a complete analysis of the static symptoms of UVD, such as spontaneous nystagmus (SN), yaw head tilt (YHT), and roll head tilt (RHT), nor have they included a dose-response analysis or vehicle controls for EGb 761. The aim of the present study was to examine the effects of the EGb 761 extract on static vestibular compensation in guinea …pig, using a dose-response analysis and both vehicle and saline controls. Analysis of variance showed that there was a significant decrease in SN frequency (P < 0.05 ) and a significant change in the rate of SN compensation (P < 0.05 ), using 3 i.p. injections of EGb 761 (25, 50, or 100 mg/kg), or vehicle, or saline, at 0, 25, and 40 h post-UVD. However, post-hoc testing revealed that this was due entirely to significant differences between the saline and vehicle groups at 35, 40, and 50 h post-UVD (P < 0.05 in all cases) and between the saline and the 100 mg/kg and 25 mg/kg EGb 761 groups at 35 and 50 h post-UVD, respectively (P < 0.05 for both comparisons); there were no significant differences between the vehicle and drug groups at any time. YHT and RHT were not significantly different between the drug, saline, and vehicle groups. In a second set of experiments, the 50 and 100 mg/kg EGb 761 i.p. injection frequencies were doubled. However, once again, neither SN nor YHT were significantly different between the EGb 761 groups and the vehicle controls. These results suggest that 1) EGb 761 does not significantly enhance or accelerate compensation of the static symptoms of UVD in guinea pig and 2) the EGb 761 vehicle may exert some effects on its own. Therefore, EGb 761 may be of limited use in the treatment of acute vestibular dysfunction in humans. Show more

Keywords: vestibular compensation, EGb 761, Ginkgo biloba

DOI: 10.3233/VES-1999-9205

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 111-118, 1999

Authors: Hirvonen, Timo P | Aalto, Heikki | Pyykkö, Ilmari | Juhola, Martti

Article Type: Research Article

Abstract: The head autorotation test is a novel method for studying the high-frequency vestibuloocular reflex without heavy machinery to generate whole-body rotation. Despite many studies with the test, the method is far from standardized, and no comparison has been made of different versions of the test. The objective of this study was to compare the vestibuloocular reflex of 100 healthy subjects measured simultaneously with two versions of the head autorotation test. Gain, phase, asymmetry, and the frequency bands reached were determined in the frequency bands of 1, 2, 3, 4, and 5 Hz. The gain measured with both tests was close …to unity (range 0.95–1.04) from 1 to 4 Hz and about 0.9 at 5 Hz. In the test developed by Vorteq the phase lagged (− 7 to − 21 ∘ ) in all the frequency bands, and it differed significantly from the phase lead of 2 to 5 ∘ that was measured by the other test. The asymmetry measured with the Vorteq test increased continuously from 1.5% variation, which was larger in the higher frequency bands. In conclusion, the high-frequency vestibuloocular reflex of healthy subjects can be quantified with active head oscillation. Both tests produced similar gain results, but the phase results differed systematically. Thus, the results of different head autorotation tests may not be directly comparable. Show more

DOI: 10.3233/VES-1999-9206

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 119-125, 1999

Authors: Marlinsky, V.V. | Reber, M. | Kröller, J.

Article Type: Research Article

Abstract: The effect of d-amphetamine oral administration in doses of 1–2.5 mg/kg on horizontal optokinetic nystagmus (OKN) and afternystagmus (OKAN) was investigated in the guinea pig. Eye movements were recorded by means of the electromagnetic search-coil technique. After amphetamine administration the range of stimulus velocities effective for eliciting OKN was 10–20 deg/s higher than before treatment. The mean values and the fluctuations of the eye velocity during slow nystagmus phases before and after treatment did not differ. Aministration of amphetamine led to 2–8 s increase in OKAN duration. The OKAN prolongation did not depend on stimulation velocity. The dependency of OKAN …duration on stimulation velocity was well approximated by a linear regression. The slope of the regression line was 0.160 ± 0.022 before and 0.177 ± 0.028 after treatment. Similarity in the coefficients indicates that amphetamine did not alter the relationship between the velocity of optokinetic stimulus and the duration of afternystagmus. Constant prolongation of OKAN over the whole range of stimulation velocities could reflect a constant shift in activity of neurons representing the velocity storage. The effects observed on OKN gain curves and the increase in OKAN duration did not display a clear dependency on the dosages of d-amphetamine used in the experiments. We assume that the effects of treatment reflected a general increase in attentiveness and motility of animals resulting from the arousal action of amphetamine. Show more

Keywords: amphetamine, OKN, OKAN, guinea pig

DOI: 10.3233/VES-1999-9207

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 127-133, 1999

Authors: Allum, J.H.J. | Ledin, T.

Article Type: Research Article

Abstract: The centrally controlled compensation for a reduced horizontal vestibulo-ocular reflex (VOR) gain caused by a unilateral afferent deficit is usually studied following a selective surgical procedure which completely lesions the vestibular nerve or blocks the horizontal semicircular canal. The more common, unilateral, vestibular deficit encountered clinically, is a partial loss of peripheral vestibular function, following which peripheral recovery and/or central compensation may occur. We investigated changes of the VOR gain in response to a sudden, idiopathic, unilateral vestibular deficit in 64 subjects by examining the responses to low-frequency, whole-body, rotations about an earth vertical axis with different accelerations (5, 20 …and 40 deg / sec 2 ) during in- and out-patient visits separated by 4 months in an attempt to identify changes brought about by peripheral recovery and by central compensation processes. Peripheral function was assumed to be measured by the response to caloric irrigation. It improved some 30% between the two visits. VOR responses for rotations towards the deficit side also improved between the two visits. Most improvement occurred for 20 deg / sec 2 accelerations. However, the correlation coefficient between rotation and caloric responses was always less than 0.6. Unlike caloric responses which improved over time, responses for rotations to the intact side did not change between the visits. For this reason, the majority of observed VOR rotation responses were nearly symmetrical at the time of the second visit, despite being below normal levels. These findings suggest that both peripheral recovery and central compensation processes help restore symmetrical VOR function for head rotations after a partial unilateral vestibular deficit. However the improvement of VOR response symmetry, particularly to slow (< 40 deg / sec 2 ) accelerations, is largely independent of the recovery of peripheral sensitivity. Show more

Keywords: peripheral vestibular deficit, vestibulo-ocular reflex, caloric tests, rotation tests, electronystagmography, neural recovery, neural plasticity

DOI: 10.3233/VES-1999-9208

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 135-144, 1999

Authors: Vibert, D. | Häusler, R. | Safran, A.B.

Article Type: Research Article

Abstract: In humans, the perception of vertical is provided by input from various sensorineural organs and pathways: vision, eye-movements, and proprioceptive and vestibular cues, particularly from the otolithic organs and graviceptive pathways. Well known in several types of brainstem lesions, subjective visual vertical (SVV) abnormalities may also be observed after peripheral vestibular lesions, such as surgical deafferentation, with a deviation directed toward the operated ear. Subjective visual vertical abnormalities are presumably related to a lesion of the otolithic organs and/or to changes in the afferent graviceptive pathways. The goal of this prospective study was to measure the SVV and to define …the influence of the otolithic organs in patients suffering from various types of peripheral vestibular diseases: unilateral sudden cochleo-vestibular loss, so-called “viral labyrinthitis” (VL), sudden idiopathic unilateral peripheral vestibular loss, so-called “vestibular neuritis” (Ne). Data were compared with findings after unilateral surgical deafferentations such as vestibular neurectomy (VN) and labyrinthectomy (Lab). Subjective visual vertical was measured with a binocular test (vertical frame) and a monocular test (Maddox rod). In all patients, after VN and Lab, the SVV showed a 10 – 30 ∘ tilt with the vertical frame (N: 0 ± 2 ∘ ), 5 – 15 ∘ with the Maddox rod (N: 0 ± 4 ∘ ). With the vertical frame, SVV was tilted > 2 ∘ in VL (47%) VL (41%) Our results demonstrate that SVV is frequently tilted in acute peripheral vestibulopathies such as VL and Ne. These findings suggest that otolithic function is implicated in the deficit depending on the extent and/or the localisation of the peripheral vestibular lesion. Show more

Keywords: subjective visual vertical, otolithic organs, peripheral vestibular diseases

DOI: 10.3233/VES-1999-9209

Citation: Journal of Vestibular Research, vol. 9, no. 2, pp. 145-152, 1999