Journal of Vestibular Research - Volume 13, issue 2-3

Authors: Miyashita, Misao | Suzuki-Inatomi, Takami | Hirai, Naoki

Article Type: Research Article

Abstract: The effect of postural changes on respiration was investigated in ten anesthetized cats by applying body tilting during the inspiration phase while recording respiratory patterns, as given by the diaphragmatic EMG, together with either the lung volume or the air flow temperature. The results show that the head-up tilting during inspiration reduced the period of the inspiratory phase and increased the end-inspiratory lung volume. On the other hand, the head-down tilting during inspiration had opposite effects. These effects disappeared after transection of the vagus nerve. However, labyrinthectomy did not diminish the effects, probably because of functional suppression of the vestibular …system due to the anesthetic. When correlating the activity of 15 vagal afferents presumably originating from the slowly adapting lung stretch receptors with lung volume changes during tilting, their maximum firing rate (87 ± 15.7 Hz) was increased with an increase in the lung inflation volume and was attained earlier on head-up tilting and it was reduced with a decrease of the lung volume on head-down tilting (63 ± 16.6 Hz) as compared with the value in the horizontal position (74 ± 14.2 Hz). These results suggest that respiratory modulation during head-up or head-down tilting is consistent with the Hering-Breuer reflexes and minimizes the externally induced lung volume changes during postural changes. Show more

Keywords: respiration, Hering-Breuer reflex, slowly adapting pulmonary stretch receptors, posture, tilting, cat

DOI: 10.3233/VES-2003-132-301

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 57-64, 2003

Authors: Young, Laurence R. | Sienko, Kathleen H. | Lyne, Lisette E. | Hecht, Heiko | Natapoff, Alan

Article Type: Research Article

Abstract: Head movements made while the whole body is rotating at unusually high angular velocities (here with supine body position about an earth-vertical axis) result in inappropriate eye movements, sensory illusions, disorientation, and frequently motion sickness. We investigated the acquisition and retention of sensory adaptation to cross-coupled components of the vestibulo-ocular reflex (VOR) by asking eight subjects to make headturns while being rotated at 23 rpm on two consecutive days, and again a week later. The dependent measures were inappropriate vertical VOR, subjective tilt, and motion sickness in response to 90° yaw out-of-plane head movements. Motion sickness was evaluated during and …following exposure to rotation. Significant adaptation effects were found for the slow phase velocity of vertical nystagmus, the reported magnitude of the subjective tilt experienced during head turns, and motion-sickness scores. Retention of adaptation over a six-day rest period without rotation occurred, but was not complete for all measures. Adaptation of VOR was fully maintained while subjective tilt was only partially maintained and motion-sickness scores continued to decrease. Practical implications of these findings are discussed with particular emphasis on artificial gravity, which could be produced in weightlessness by means of a short-radius (2 m) rotator. Show more

Keywords: artificial gravity, adaptation, centrifugation, vestibulo-ocular reflex, illusory tilt

DOI: 10.3233/VES-2003-132-302

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 65-77, 2003

Authors: Ramat, Stefano | Schmid, Roberto | Zambarbieri, Daniela

Article Type: Research Article

Abstract: Passive head rotation in darkness produces vestibular nystagmus, consisting of slow and quick phases. The vestibulo-ocular reflex produces the slow phases, in the compensatory direction, while the fast phases, in the same direction as head rotation, are of saccadic origin. We have investigated how the saccadic components of the ocular motor responses evoked by active head rotation in darkness are generated, assuming the only available sensory information is that provided by the vestibular system. We recorded the eye and head movements of nine normal subjects during active head rotation in darkness. Subjects were instructed to rotate their heads in …a sinusoidal-like manner and to focus their attention on producing a smooth head rotation. We found that the desired eye position signal provided to the saccadic mechanism by the vestibular system may be modeled as a linear combination of head velocity and head displacement information. Here we present a mathematical model for the generation of both the slow and quick phases of vestibular nystagmus based on our findings. Simulations of this model accurately fit experimental data recorded from subjects. Show more

DOI: 10.3233/VES-2003-132-303

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 79-91, 2003

Authors: Bacal, Kira | Billica, Roger | Bishop, Sheryl

Article Type: Research Article

Abstract: Neurovestibular symptoms experienced by astronauts in the post-flight period were examined using data from medical debriefs contained in the NASA Longitudinal Study of Astronaut Health database. Ten symptoms were identified (clumsiness, difficulty concentrating, persisting sensation aftereffects, nausea, vomiting, vertigo while walking, vertigo while standing, difficulty walking a straight line, blurred vision, and dry heaves), of which eight were crossed with twelve demographic parameters (mission duration, astronaut gender, age, one-g piloting experience, previous space flight experience, g-suit inflation, g-suit deflation, in-flight space motion sickness, in-flight exercise, post-flight exercise, mission role, fluid loading). Three symptoms were experienced by a majority of subjects, …and another two by more than a quarter of the subjects. Intensity of the symptoms was mild, suggesting that they are unlikely to pose a risk to the crew during landing and the post-flight period. Seven of the symptoms and eight of the parameters under study were found to be significantly associated with each other. Show more

DOI: 10.3233/VES-2003-132-304

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 93-102, 2003

Authors: Gordon, Carlos R. | Doweck, Ilana | Nachum, Zohar | Gonen, Adi | Spitzer, Orna | Shupak, Avi

Article Type: Research Article

Abstract: Betahistine was evaluated for the prevention of seasickness in a laboratory and sea study. The effect of 48 mg betahistine on the vestibulo-ocular reflex (VOR) and on psychomotor performance was evaluated in twelve young healthy subjects in a double-blind, placebo controlled, randomized, crossover design. The vestibulo-ocular reflex was evaluated by the Sinusoidal Harmonic Acceleration (SHA) test at frequencies of 0.01, 0.02, 0.04, 0.08 and 0.16 Hz. Psychomotor performance was assessed by both computerized and paper and pencil test batteries. No significant differences in VOR gain or phase were found between betahistine and placebo treatment for any of the frequencies tested. …No significant differences were found between treatments for any of the psychomotor performance tests or other possible side effects. The effect of 48 mg betahistine on seasickness severity was evaluated in 83 subjects during a voyage in rough seas. Betahistine had a borderline non-statistically significant effect on the prevention of seasickness in comparison with placebo (p = 0.053), with no notable side effects. Although our results are insufficient to recommend betahistine as an anti-seasickness drug, further studies are required to determine its possible effectiveness in less provocative motion sickness situations. Show more

Keywords: betahistine, motion sickness, seasickness

DOI: 10.3233/VES-2003-132-305

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 103-111, 2003

Authors: Enticott, J.C. | Dowell, R.C. | O'Leary, S.J.

Article Type: Research Article

Abstract: This study considered whether the monothermal (MT) caloric test could predict the normality of the full conventional bithermal (BT) caloric test, and therefore be an alternative to full caloric investigation. This would have the advantages of reducing test time and patient discomfort as only two caloric tests would be needed instead of four. 744 BT caloric investigations were examined, and the unilateral weakness and directional preponderance calculated for the BT and the MT stimuli. By defining the BT results as the standard, the false-positive and false-negative results of the MT test were derived. Overall using very strict MT difference criteria …of less than 5% and no spontaneous nystagmus, false-negative rates for the cool MT were very low (< 1%) and better than the warm MT (< 7.1%) suggesting that the cool MT was a reliable screen test. However, unacceptably high false-positive rates were produced reflecting more than 3/4 of normal BT results failing the MT criterion. This unacceptable false-positive rate decided against implementing the MT test at our facility. The results of this study however have guided the use of the cool air-stimulus first during BT testing and, when completion of the BT is not possible or inadvisable, satisfying the stringent MT criterion confidently indicates with a probability of > 99% the absence of an abnormal BT result. Show more

Keywords: monothermal, bithermal, caloric test, vestibular

DOI: 10.3233/VES-2003-132-306

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 113-119, 2003

Authors: Brantberg, Krister | Tribukait, Arne | Fransson, Per-Anders

Article Type: Research Article

Abstract: In recent years it has been demonstrated that loud clicks generate short latency vestibular evoked myogenic potentials (VEMP). It has also been demonstrated that skull tap stimulation evokes similar VEMP. In the present study, the differences between the click-induced and the skull-tap induced VEMP were studied in 18 patients at onset of vestibular neuritis. Gentle skull taps were delivered manually above each ear on the side of the skull and on the forehead midline. The muscular responses were recorded over both sternocleidomastoid muscles using skin electrodes. Abnormal skull tap VEMP were found in the majority of the patients (10/18, 56%). …However, only 4/18 (22%) showed asymmetry in the click-induced VEMP. The high percentage of abnormal skull tap VEMP might suggest that this response is not only dependent on the inferior division of the vestibular nerve, because the inferior division of this nerve is usually spared in vestibular neuritis. Moreover, the patients with abnormals kull tap VEMP differed from those with normal VEMP in their settings of the subjective visual horizontal with static head tilt in the roll plane. This might suggest that skull tap VEMP are (also) related to utricular function. Show more

Keywords: vestibular neuritis, VEMP, skull taps, sacculus, utriculus, vestibulocollic

DOI: 10.3233/VES-2003-132-307

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 121-130, 2003

Authors: Gianna-Poulin, Claire C. | Stallings, Valerie | Black, F. Owen

Article Type: Research Article

Abstract: This study assessed the eye movement responses to active head rotation in six subjects with complete unilateral vestibular loss (UVL), five subjects with posterior canal plugging (PCP) and age- and sex-matched normal subjects. Subjects performed head rotations in the pitch and yaw planes at frequencies ranging from 2 to 6 Hz, while looking at an earth-fixed target. Vertical eye movement gains obtained in UVL, PCP and normal subjects were not significantly different. Vertical phases decreased with increasing head movement frequencies in both UVL and PCP subjects. Although this decrease produced significantly different vertical phases between UVL and normal subjects for …head movements above 3.9 Hz, vertical phases in some normal subjects were similar to those obtained in UVL subjects. We conclude that active head oscillations in the pitch plane are not clinically useful for the detection of vertical canal impairment limited to one ear. As expected, UVL subjects showed reduced horizontal gains, and eye velocity asymmetries during active head rotation in the yaw plane. Results in some PCP subjects suggested possible minor impairments of horizontal vestibulo-ocular reflexes. Show more

Keywords: vestibular, active head rotation, posterior canal, unilateral, human

DOI: 10.3233/VES-2003-132-308

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 131-141, 2003

Authors: Furman, Joseph M. | Hsu, Li-Chi | Whitney, Susan L. | Redfern, Mark S.

Article Type: Research Article

Abstract: The chronic effects of unilateral peripheral vestibular loss (UPVL) are influenced by vestibular compensation. This study documents the balance-related symptoms and quantitative vestibular laboratory testing of 20 patients with surgically confirmed UPVL. Included are measures of the semicircular canal-ocular reflex, the otolith-ocular reflex, and both static and dynamic semicircular canal-otolith-interaction. This study differs from previous studies of patients with UPVL in that a large number of patients with surgically confirmed lesions were tested with three types of off-vertical axis rotation, several of the patients had anatomically preserved superior vestibular nerves, and self-perceived level of disability related to dizziness and imbalance …were available. Results confirmed previously reported changes in the vestibulo-ocular reflex of patients with UPVL. Also, there was no apparent effect of anatomically preserving the superior vestibular nerve during surgical resection of vestibular schwannomas based on either subjective or objective measures of vestibular dysfunction. Further, there were no apparent correlations between subjective measures of dizziness and imbalance and objective measures of vestibulo-ocular function. These results have clinical implications for the management of patients with unilateral vestibular loss and provide insights into the process of vestibular compensation especially with respect to the otolith-ocular reflex. Show more

Keywords: vestibulo-ocular, Acoustic neuroma, Off-vertical axis rotation

DOI: 10.3233/VES-2003-132-309

Citation: Journal of Vestibular Research, vol. 13, no. 2-3, pp. 143-151, 2003