Journal of Vestibular Research - Volume 18, issue 4

Authors: Holly, Jan E. | Vrublevskis, Arturs | Carlson, Lindsay E.

Article Type: Research Article

Abstract: Illusory perceptions of motion and orientation arise during human centrifuge runs without vision. Asymmetries have been found between acceleration and deceleration, and between forward-facing and backward-facing runs. Perceived roll tilt has been studied extensively during upright fixed-carriage centrifuge runs, and other components have been studied to a lesser extent. Certain, but not all, perceptual asymmetries in acceleration-vs-deceleration and forward-vs-backward motion can be explained by existing analyses. The immediate acceleration-deceleration roll-tilt asymmetry can be explained by the three-dimensional physics of the external stimulus; in addition, longer-term data has been modeled in a standard way using physiological time constants. However, …the standard modeling approach is shown in the present research to predict forward-vs-backward-facing symmetry in perceived roll tilt, contradicting experimental data, and to predict perceived sideways motion, rather than forward or backward motion, around a curve. The present work develops a different whole-motion-based model taking into account the three-dimensional form of perceived motion and orientation. This model predicts perceived forward or backward motion around a curve, and predicts additional asymmetries such as the forward-backward difference in roll tilt. This model is based upon many of the same principles as the standard model, but includes an additional concept of familiarity of motions as a whole. Show more

Keywords: Perception, self-motion, model, centrifuge, VOR

DOI: 10.3233/VES-2008-18401

Citation: Journal of Vestibular Research, vol. 18, no. 4, pp. 171-186, 2008

Authors: Ward, Bryan K. | Redfern, Mark S. | Jennings, J. Richard | Furman, Joseph M.

Article Type: Research Article

Abstract: The purpose of this study was to further investigate the mechanism of the influence of concurrent cognitive tasks on eye movements induced by earth-vertical axis rotation (EVAR) in young and older participants. Ten young (ages 21–34), ten young-old (ages 65–74) and nine older participants (ages 75–84) each performed five different cognitive tasks during sinusoidal EVAR in darkness at 0.02 Hz for three cycles, 0.05 Hz for four cycles, and 0.1 Hz for five cycles, all at a peak velocity of 50 degrees per second. The five tasks differed from one another in terms of their inherent sensory and …motor components and were designed to provide insight into the effect of cognitive processing on VOR dynamics. Tasks included auditory frequency and lateralization disjunctive reaction time (DRT) tasks, silent and audible backward counting, and a question-response clinical standard task. For the DRT trials, tones were presented to the participant through earphones. Participants were instructed to respond as accurately and as quickly as possible. Eye movements were recorded with electro-oculography and calibrations were performed before and after every five rotations in all subjects. Participants had an increase in VOR phase lead while performing DRT tasks as compared to the clinical standard and counting tasks. The effect was most noticeable at the 0.02 Hz frequency and was present in all age groups. In addition, we observed a decrease in VOR gain while subjects performed auditory DRT tasks during EVAR at 0.02 Hz, 0.05 Hz and 0.1 Hz as compared to the clinical standard and counting tasks. These results suggest cognitive task-dependent interference between central auditory processing and vestibular processing primarily at the sensory rather than at the motor level. Show more

DOI: 10.3233/VES-2008-18402

Citation: Journal of Vestibular Research, vol. 18, no. 4, pp. 187-195, 2008

Authors: Maes, Leen | Dhooge, Ingeborg | De Vel, Eddy | D'haenens, Wendy | Bockstael, Annelies | Keppler, Hannah | Philips, Birgit | Swinnen, Freya | Vinck, Bart M.

Article Type: Research Article

Abstract: Rotational testing has been used in clinical practice to explore vestibular function. Frequently used stimulus algorithms include: sinusoidal harmonic acceleration test (SHAT), pseudorandom rotation test (PRRT), and velocity step test (VST). The aim of this study was to construct normative data as well as to evaluate the test-retest reliability of those rotational paradigms. One hundred and fifty subjects without vestibular history participated in the normative study. The SHAT was presented at 5 frequencies (0.01, 0.02, 0.05, 0.1, 0.2 Hz), whereas for the PRRT those frequencies were summed. The VST consisted of a rotation to the right and left and was …administered twice. Thirty-two volunteers were retested to assess the test-retest reliability. Separate normative data were needed according to sex, stimulus type, and frequency for the SHAT and PRRT, and according to stimulus and direction for the VST. High reliability by means of the intraclass correlation coefficient (ICC) and the method error (ME) was obtained for the SHAT, PRRT, and VST gain, SHAT phase and asymmetry, and VST time constant parameters. The availability of data on the minimal detectable test-retest differences supports the evaluation of rotational responses on a retest session. Show more

Keywords: Rotational paradigms, sinusoidal harmonic acceleration test (SHAT), pseudorandom rotation test (PRRT), velocity step test (VST), normative, reliability, intraclass correlation coefficient (ICC), method error (ME), minimal detectable difference (MDD)

DOI: 10.3233/VES-2008-18403

Citation: Journal of Vestibular Research, vol. 18, no. 4, pp. 197-208, 2008

Authors: Fransson, P.A. | Patel, M. | Magnusson, M. | Berg, S. | Almbladh, P. | Gomez, S.

Article Type: Research Article

Abstract: Sleep restrictions and sleep deprivation have become common in modern society, as many people report daily sleep below the recommended 8 hours per night. This study aimed to examine the effects of sleep deprivation on oculomotor performance by recording smooth pursuit and saccadic eye movements after 24 and 36 hours of sleep deprivation. Another objective was to determine whether detected changes in oculomotor performance followed fluctuations according to a circadian rhythm and/or subjective Visuo-Analogue sleepiness Scale scores. Oculomotor responses were recorded from 18 subjects using electronystagmography, and comprised measurements of accuracy (i.e., the percentage of time the eye movement velocity …was within the target velocity boundaries), velocity and latency. Continuous EEG recordings were used to validate that subjects had remained awake throughout the 36-hour period. Our findings showed that sleep deprivation deteriorated smooth pursuit gain, smooth pursuit accuracy and saccade velocity. Additionally, the ratio between saccade velocity and saccade amplitude was significantly decreased by sleep deprivation. However, as the length of sleep deprivation increased, only smooth pursuit gain deteriorated further, whereas there were signs of improvement in smooth pursuit accuracy measurements. The latter observation suggests that smooth pursuit accuracy might be affected by the circadian rhythm of alertness. Surprisingly, high subjective scores of sleepiness correlated in most cases with better saccade performance, especially after 36 hours of sleep deprivation, suggesting that awareness of sleepiness might make subjects perform better during saccade assessments. To conclude, oculomotor function clearly decreased after sleep deprivation, but the performance deteriorations were complex and not necessarily correlated with subjectively felt sleepiness. Show more

Keywords: Oculomotor, smooth pursuit, saccadic, sleep deprivation

DOI: 10.3233/VES-2008-18404

Citation: Journal of Vestibular Research, vol. 18, no. 4, pp. 209-222, 2008

Authors: Aoki, Mitsuhiro | Sakaida, Yuzuru | Hayashi, Hisamitsu | Yamada, Nansei | Mizuta, Keisuke | Ito, Yatsuji

Article Type: Research Article

Abstract: Objectives: A number of animal studies have confirmed that the otolith organs may contribute to the maintenance of blood pressure during positional change; however, the contribution of such organs remains to be elucidated in humans. Methods: This study investigated whether acute dizzy patients (n = 11) with an abnormal deviation of the subjective visual vertical (SVV) show an abnormality in the orthostatic regulation of blood pressure in comparison to acute dizzy patients with a normal deviation of the SVV (n = 11) and control subjects (n = 11). Results: The average change in the …systolic blood pressure (SBP) at 1 minute after active standing in comparison to that at baseline in dizzy patients with an abnormal deviation of the SVV was −6.8 ± 3.0 mmHg. The change was significantly lower than that in the control subjects (2.1 ± 2.6 mmHg, p < 0.05), while the change in dizzy patients with a normal deviation of the SVV (2.6 ± 2.2 mmHg) was not significantly different from that in the control subjects (p > 0.05). Active standing significantly increased the heart rate (HR) in all participants (p < 0.01) and there was no significant difference in the change of the HR among the 3 groups (p > 0.05). Conclusions: These results suggest that dizzy patients in the acute phase of recovery from vestibular dysfunction have an orthostatic dysregulation of the blood pressure, thus resulting in such patients suffering from orthostatic intolerance. Show more

Keywords: Vestibular lesion, subjective visual vertical, orthostatic dysregulation, human

DOI: 10.3233/VES-2008-18405

Citation: Journal of Vestibular Research, vol. 18, no. 4, pp. 223-229, 2008

Authors: Jacot, E. | Wiener-Vacher, S.

Article Type: Research Article

Abstract: Purpose: Showing the interest of vestibular evoked myogenic potentials in paediatric neurological vestibulospinal pathology detection and followup. Materials and methods: The vestibular evoked myogenic potentials testing apparatus presented is now commonly used in ENT clinics for patients from 1 month of age. Our system and protocol permits control to evoke and select the best EMG level and makes possible a comparison of data from different sides or level of stimulation or different sessions. Normal vestibular evoked myogenic potentials latencies obtained with tone bursts were remarkably stable (P: 13 +/− 0.8 ms, N: 19.6 +/− 1.6 ms). The …reported case illustrates abnormal vestibular evoked myogenic potentials latencies in neuropathy. Results: A 6 y.o. child with progressive imbalance was referred to the ENT department for vestibular functional evaluation. Abnormally long latencies in the vestibular evoked myogenic potentials and neurological examination oriented the diagnosis towards Guillain-Barre syndrome and immediate referral to a neurology department. Vestibular evoked myogenic potentials also helped to monitor the neurological recovery. Conclusion: The present case shows the potential value of vestibular evoked myogenic potentials in diagnosis and evaluation of descending brainstem pathways in neuropathies like Guillain-Barre syndrome in complement to neurological evaluation. Show more

Keywords: Guillain-Barre syndrome, VEMP latencies, ataxia, imbalance, brainstem, diagnosis, vestibular evaluation

DOI: 10.3233/VES-2008-18406

Citation: Journal of Vestibular Research, vol. 18, no. 4, pp. 231-237, 2008