Journal of Vestibular Research - Volume 23, issue 1

Article Type: Editorial

DOI: 10.3233/VES-130472

Citation: Journal of Vestibular Research, vol. 23, no. 1, pp. 1-1, 2013

Authors: Tomilovskaya, E.S. | Berger, M. | Gerstenbrand, F. | Kozlovskaya, I.B.

Article Type: Research Article

Abstract: The aim of the study was to examine effects of long-duration exposure to weightlessness on characteristics of the vertical gaze fixation reaction (GFR). The subjects were to perform the target acquisition task on visual stimuli that appeared at a distance of 16 deg. up- and down from the primary position in a random order. Experiments were performed before launch, during flight and after landing. Before flight time of gaze fixation reaction did not exceed 650 ms. During space flight (SF) it extended up to 900–1000 ms and more. The velocities of head movement in space decreased, but the velocities of …eye counterrotation decreased to a lesser degree. This difference resulted in sharp increase of vertical vestibular ocular reflex (VOR) gain (up to 4.3 values in one of the cosmonauts) during the 1st month of flight; further it decreased reaching the values of 0.5–0.7 on the 5th month of SF. After landing vertical VOR gain increased greatly again. These results in the vertical axis are in agreement with the data of Kozlovskaya et al., which showed in experiments with monkeys that horizontal VOR gain increased together with redundant inadequate responses of vestibular nucleus on vestibular stimulation and that in the course of adaptation to these conditions central nervous system inhibited vestibular input from the motor control system. Show more

Keywords: Vertical gaze fixation reaction, vestibular-ocular reflex, eye-head coordination, weightlessness, space flight

DOI: 10.3233/VES-130470

Citation: Journal of Vestibular Research, vol. 23, no. 1, pp. 3-12, 2013

Authors: Clément, Gilles | Wood, Scott J.

Article Type: Research Article

Abstract: Constant velocity off-vertical axis rotation (OVAR) provides dynamic linear acceleration stimuli that can be used to assess otolith function. Eight astronauts were rotated in darkness about their longitudinal axis 20° off vertical at low (0.125 Hz) and high (0.5 Hz) frequencies and their responses were compared before and after spaceflight. Eye movements were recorded using infrared videography and perceived motion was evaluated using a joystick with four degrees of freedom – pitch and roll tilt, front-back and lateral translation. Low-frequency OVAR generates tilt otolith-induced responses – modulation of ocular counter-roll and counter-pitch with perceived conical motion path – whereas high-frequency …OVAR generates translational otolith-induced responses – modulation of horizontal and vergence slow phase velocity with perceived cylindrical motion path. While there were transient changes in the amplitude of the translational ocular responses on landing day, there were no major changes in the tilt ocular reflexes after adaptation to weightlessness. However, there was an increase in sensitivity to motion perception after spaceflight. Direct comparisons of pre- and postflight stimuli suggested that OVAR on landing day was less provocative of motion sickness than before spaceflight. These results confirm that some otolith reflexes elicited during passive motion may not be altered by short-duration spaceflight – or may readapt very quickly – and that the resolution of sensory conflict associated with postflight recovery involves higher-order neural processes. Show more

Keywords: OVAR, otolith, spatial orientation, microgravity

DOI: 10.3233/VES-130471

Citation: Journal of Vestibular Research, vol. 23, no. 1, pp. 13-22, 2013

Authors: Buytaert, K.I. | MacDougall, H.G. | Moore, S.T. | Clement, G. | Pattyn, N. | Migeotte, P.-F. | Wuyts, F.L.

Article Type: Research Article

Abstract: In the framework of further space exploration, countermeasures to combat the drawbacks of human space flights are essential. The present study focuses on the influence of microgravity on the otolith-ocular reflex and aims to test the hypothesis of artificial gravity being an adequate countermeasure for the deconditioning of the aforementioned reflex. The so-called SPIN study, commissioned by the European Space Agency, can be considered as a control experiment in the broad sense for the Neurolab mission (STS-90) during which 4 crewmembers of the space shuttle were subjected to in-flight centrifugation on the visual and vestibular investigation system (VVIS). After their …nearly 16-day mission, they did not suffer from orthostatic intolerance and spatial disorientation. In addition, the relevant parameters of the otolith-ocular interaction remained unaffected. For this study cosmonauts from a long duration stay in the International Space Station that were not centrifuged in-flight were tested on the VVIS (1 g centripetal interaural acceleration) on 6 different days. Three measurements were taken about 1.5–2 months prior to launch and 3 were taken at 1, 4 and 9 days after return from space. Ocular counter-rolling was measured before, during and after rotation on the VVIS using infrared video goggles and compared pair wise using Friedman tests. The perception of verticality was monitored using an ultrasound system for perceptual evaluation. The preliminary results of 4 cosmonauts showed a surprisingly large inter-individual variability of the measurements. Although OCR and perception of verticality appeared to be influenced overall by the exposure to microgravity, the wide variability among the cosmonauts obscured any statistical significance, in particular due to one cosmonauts being inconsistent with the other 3. Despite the specificity of the tests under normal conditions, the diverse response to spaceflight of our subjects exposes the complexity of the peripheral and central neural adaptive processes. Show more

Keywords: Otolith-ocular interaction, artificial gravity, VVIS, space motion sickness

DOI: 10.3233/VES-130469

Citation: Journal of Vestibular Research, vol. 23, no. 1, pp. 23-31, 2013

Authors: Adamo, Diane E. | Pociask, Fredrick D. | Goldberg, Allon

Article Type: Research Article

Abstract: Postural control requires the integration of sensory information and is essential for performing every day movements and activities. Integrating sensory information from multiple sources may be challenging when competing sources of sensory information are affected. To further understand this complex relationship, this study investigated the contribution of varying sources of sensory information to postural control in healthy, young participants. Sixty young healthy adults (n=22 males; mean age, 24.6 ± 2.1 SD years and (n=38 females, mean age 24.0 ± 1.4 SD years) were asked to maintain a stable posture under conditions that varied standing surface, head position and the availability …of visual information. Sway velocity was largest when standing on foam with eyes closed and head extended (2.07°/s) however, under the same visual-surface conditions with the head in a neutral position, sway velocity (1.59°/s) was smaller yet remained significant. Findings from this study suggest that postural sway responses are dependent on the combined integration of available sources of sensory information. It is anticipated that such baseline information will allow us to apply our findings to the clinical management of individuals suffering from balance and vestibular impairments. Show more

Keywords: Balance, postural control, head extended

DOI: 10.3233/VES-130473

Citation: Journal of Vestibular Research, vol. 23, no. 1, pp. 33-40, 2013

Authors: Dumas, Georges | Lion, Alexis | Gauchard, Gérome C. | Herpin, Guillaume | Magnusson, Måns | Perrin, Philippe P.

Article Type: Research Article

Abstract: Skull vibration induces nystagmus in unilateral vestibular lesion (UVL) patients. Vibration of skull, posterior cervical muscles or inferior limb muscles alters posture in recent UVL patients. This study aimed to investigate the postural effect of vibration in chronic compensated UVL patients. Vibration was applied successively to vertex, each mastoid, each side of posterior cervical muscles and of triceps surae in 12 UVL patients and 9 healthy subjects. Eye movements were recorded with videonystagmography. Postural control was evaluated in eyes open (EO) and eyes closed (EC) conditions. Sway area, sway path, anteroposterior and medio-lateral sways were recorded. A …vibration induced nystagmus (VIN) beating toward the healthy side was obtained for each UVL patient during mastoid vibration. In EO, only sway path was higher in UVL group during vibration of mastoids and posterior cervical muscles. The EO postural impairments of UVL patients could be related to the eye movements or VIN, leading to visual perturbations, or to a proprioceptive error signal, providing an erroneous representation of head position. The vibration-induced sway was too small to be clinically useful. Vestibulo-ocular reflex observed with videonystagmography during mastoid vibration seems more relevant to reveal chronic UVL than vestibulo-spinal reflex observed with posturography. Show more

Keywords: Inner ear, compensation, nystagmus, posturography, videonystagmography

DOI: 10.3233/VES-130468

Citation: Journal of Vestibular Research, vol. 23, no. 1, pp. 41-49, 2013

Authors: Whitney, Susan L. | Sparto, Patrick J. | Cook, James R. | Redfern, Mark S. | Furman, Joseph M.

Article Type: Research Article

Abstract: Introduction: People with vestibular disorders often experience space and motion discomfort when exposed to moving or highly textured visual scenes. The purpose of this study was to measure the type and severity of symptoms in people with vestibular dysfunction during coordinated head and eye movements in optic flow environments. Methods: Seven subjects with vestibular disorders and 25 controls viewed four different full-field optic flow environments on six different visits. The optic flow environments consisted of textures with various contrasts and spatial frequencies. Subjects performed 8 gaze movement tasks, including eye saccades, gaze saccades, and gaze stabilization tasks. …Subjects reported symptoms using Subjective Units of Discomfort (SUD) and the Simulator Sickness Questionnaire (SSQ). Self-reported dizziness handicap and space and motion discomfort were also measured. Results/conclusion: Subjects with vestibular disorders had significantly greater discomfort, oculomotor and disorientation symptoms, with some amount of symptoms in 55–60% of the trials, compared with control subjects, who had symptoms in less than 20% of the trials. The magnitude of the symptoms increased during each visit, but did not depend on the optic flow condition. Subjects who reported greater dizziness handicap and space and motion discomfort had greater severity of symptoms during the experiment (Spearman rho > 0.78). Compared with controls, subjects with vestibular disorders had about 10 deg less head excursion during the gaze saccade tasks. Overall, performance of gaze pursuit and gaze stabilization tasks in moving visual environments elicited greater symptoms in subjects with vestibular disorders compared with healthy subjects. Show more

Keywords: VOR, virtual reality, simulator sickness

DOI: 10.3233/VES-130466

Citation: Journal of Vestibular Research, vol. 23, no. 1, pp. 51-60, 2013