Journal of Vestibular Research - Volume 6, issue 5

Article Type: Other

DOI: 10.3233/VES-1996-6508

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. I-II, 1996

Authors: Koizuka, Izumi | Schor, Robert H. | Furman, Joseph M.

Article Type: Research Article

Abstract: The duration of post-rotatory nystagmus is known to be shortened by head tilt, a phenomenon that has been attributed to rapid discharge of the velocity storage mechanism. The relative importance of the various sensory signals associated with post-rotatory head tilt is unknown. Using both earth-vertical axis and off-vertical axis rotation, we investigated this issue in humans by combining sudden termination of constant velocity rotation with several post-rotatory maneuvers that stimulated combinations of otolith organ, somatosensory, and vertical semicircular canal afferents. Results indicated that horizontal post-rotatory nystagmus was shortened by maneuvers that move the head from upright to off-vertical and by …cessation of dynamic otolith stimuli. Somatosensory, neck afferent, and transient vestibular stimulation had no consistent effect. We conclude that tilt suppression of postrotatory nystagmus and the short time constant following off-vertical axis rotation is primarily a function of otolith influence on the velocity storage system. Show more

Keywords: vestibulo-ocular reflex, otolith-ocular, nystagmus

DOI: 10.3233/VES-1996-6501

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. 319-329, 1996

Authors: Kennedy, Robert S. | Hettinger, Lawrence J. | Harm, Deborah L. | Ordy, J. Mark | Dunlap, William P.

Article Type: Research Article

Abstract: Vection (V) refers to the compelling visual illusion of self-motion experienced by stationary individuals when viewing moving visual surrounds. The phenomenon is of theoretical interest because of its relevance for understanding the neural basis of ordinary self-motion perception, and of practical importance because it is the experience that makes simulation, virtual reality displays, and entertainment devices more vicarious. This experiment was performed to address whether an optokinetically induced vection illusion exhibits monotonic and stable psychometric properties and whether individuals differ reliably in these (V) perceptions. Subjects were exposed to varying velocities of the circular vection (CV) display in an optokinetic …(OKN) drum 2 meters in diameter in 5 one-hour daily sessions extending over a 1 week period. For grouped data, psychophysical scalings of velocity estimates showed that exponents in a Stevens' type power function were essentially linear (slope =0.95) and largely stable over sessions. Latencies were slightly longer for the slowest and fastest induction stimuli, and the trend over sessions for average latency was longer as a function of practice implying time course adaptation effects. Test-retest reliabilities for individual slope and intercept measures were moderately strong (r=0.45) and showed no evidence of superdiagonal form. This implies stability of the individual circularvection (CV) sensitivities. Because the individual CV scores were stable, reliabilities were improved by averaging 4 sessions in order to provide a stronger retest reliability (r=0.80). Individual latency responses were highly reliable (r=0.80). Mean CV latency and motion sickness symptoms were greater in males than in females. These individual differences in CV could be predictive of other outcomes, such as susceptibility to disorientation or motion sickness, and for CNS localization of visual-vestibular interactions in the experience of self-motion. Show more

Keywords: vection, self-motion, disorientation, neural

DOI: 10.3233/VES-1996-6502

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. 331-341, 1996

Authors: Mann, Gwendolyn C. | Whitney, Susan L. | Redfern, Mark S. | Borello-France, Diane F. | Furmant, Joseph M.

Article Type: Research Article

Abstract: The purpose of this study was to compare functional reach distance and right single leg stance time in patients who had peripheral vestibular disease. Twenty-eight patients (15 female, 13 male) between the ages of 35 and 84 were asked to perform 3 trials each of functional reach (FR) and right single leg stance (SLS). SLS times were measured by a Kistler static force platform on line with a Caspar personal computer. FR distance was measured by using a free-standing 147-cm rule. In addition, each subject filled out the Dizziness Handicap Inventory (DHI). Trials were randomized to prevent fatigue or practice …effects. A Pearson product-moment correlation was performed between FR and SLS (r=0.59, P=0.001), Post hoc analyses of the first, the best, and the average scores highlighted the importance of using means for comparison in a population as variable as the vestibularly impaired. Post hoc analyses showed no correlation between the DHI score and either functional reach distance or single leg stance time. However, when the subjects were divided into groups based on DHI score (group 1 with DHI≤49/100, group 2 with DHI≥50/100) and a pooled two-sample t-test was performed, a significant difference (P=0.05) was found in functional reach distance; the subjects who reported less perception of handicap reached farther than those who reported more perception of handicap. No difference was found between the two DHI groups in single leg stance time. Post hoc correlations of functional reach and single leg stance time. Post hoc correlations of functional reach and single leg stance within the two DHI groups showed a higher correlation in group 1 (DHI≤49/100), with r equals 0.65(P≤0.01), than in group 2 (DHI≥50/100), with r equals 0.38 (P=0.20). The study found a highly significant, moderate correlation between functional reach distance and single leg stance times in patients with peripheral vestibular disease. These results support the use of FR as an additional assessment tool with patients who have peripheral vestibular disease. Show more

Keywords: peripheral vestibular disease, functional reach, single leg stance, postural control

DOI: 10.3233/VES-1996-6503

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. 343-353, 1996

Authors: Mittelstaedt, Marie-Luise | Mittelstaedt, Horst

Article Type: Research Article

Abstract: In three psychophysical experiments subjects (Ss), blindfolded and earphoned with white noise, estimated their angular speed A) after brief acceleration to constant centric or eccentric rotation, and B) after deceleration to a full stop. Ss either indicated whenever they were rotated through 180°, or manipulated the objective velocity such that the subjective one stayed constant. With Ss in an earth-vertical attitude, subjective speed declined exponentially with a time constant that depended on eccentricity in paradigm A, but not in B. The time constant depended linearly on the amount of the centrifugal force, but not on its direction. Thus, centrifugal force …has an enhancing effect on perceived angular speed. The relevant sense organs were identified with Ss in a radial, earth-horizontal attitude. The enhancing effect was minimal when the axis of rotation was caudal of the otoliths, indicating an effect of graviceptors in the trunk. This effect, just as the effect of recently discovered truncal graviceptors on the perception of posture, turned out to depend on leg position: The minimum of the enhancing effect shifted from about 30 cm to about 60 cm caudal of the otoliths, when leg position changed from flexed to extended. It is concluded that the centrifugal force, measured by otoliths and truncal graviceptors, serves to provide information on angular velocity at eccentric rotation, at least as long as the output of the velocity storage is not yet zero. Show more

Keywords: Eccentric rotation, canal-otolith interaction, perception of posture, velocity storage, idiothetic information

DOI: 10.3233/VES-1996-6504

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. 355-366, 1996

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

Article Type: Research Article

Abstract: Following a 30-minute exposure to an unusual motor strategy called “Torso Rotation” (TR), the signs and symptoms of motion sickness appear along with perceptual illusions during movement, gaze and postural instability, and a significantly reduced vestibulo-ocular response (VOR) gain. With repeated exposure to TR, the motion sickness disappears and gaze instability seems to be reduced. Is this apparent improvement in gaze stability associated with a reduction of the transient change in VOR gain? Motion sickness (subjective questionnaire) and VOR gain (passive step rotations in darkness) were measured before and repeatedly after TR on 7 consecutive days. Despite a complete loss …of symptoms in 3 to 4 days, the transient, daily change in VOR gain remained unaffected. Furthermore, there was no increase in the use of compensatory saccades. It is concluded that adaptation to TR-induced motion sickness is not the result of a change in VOR's sensitivity to TR. Show more

Keywords: motion sickness, VOR, human, adaptation

DOI: 10.3233/VES-1996-6505

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. 367-375, 1996

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

Article Type: Research Article

Abstract: Following a 30-minute exposure to an unusual motor strategy called “Torso Rotation” (TR), the signs and symptoms of motion sickness appear along with perceptual illusions during movement, gaze and postural instability, and a significantly reduced vestibulo-ocular response (VOR) gain. With repeated exposure to TR, motion sickness symptoms disappear and gaze instability seems reduced, but without any concomitant change in VOR gain. Is the reduction in gaze instability a perceptual illusion or a real, measurable phenomenon? Velocity gain (eye velocity/head velocity) was evaluated during voluntary head shaking in the light over the frequency range 0.3 to 3.0 Hz. A significant improvement …was seen after 3 days of testing (P<0.01). Furthermore, the time course of improvement in gaze stability was correlated with the loss of motion sickness symptoms reported in the previous study (1). We suggest that adaptation to motion sickness could be related to an overall change in sensorimotor strategy, perhaps including a de-emphasis of a vestibular reference. Show more

Keywords: gaze control, human, motion sickness, adaptation

DOI: 10.3233/VES-1996-6506

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. 377-385, 1996

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

Article Type: Research Article

Abstract: “Torso Rotation” (TR) produces an acute, reversible change in human vestibular function. Experiments were performed to determine if repeated exposure to this technique would result in long-term adaptive modifications. In one experiment, VOR gain was evaluated. Measurements were obtained before and 3 times after 30 minutes of TR, on 7 consecutive days. VOR gain dropped each day after TR, returning to normal within about 20 min. In a separate experiment with different subjects, eyes-open gaze stability was measured during voluntary head shaking between 3.0 and 0.3 Hz. The same test schedule was used. Analysis of gaze stability (limited to frequencies …between 1.0 and 2.0 Hz) was complicated by an unexpected finding. Despite careful instructions, head displacement increased each day after TR, also returning to normal within about 20 min. Surprisingly, subjects were unaware of this change. Combining the 2 experiments, VOR gain and head amplitude were averaged across all 7 days, separately for the 4 daily tests. Head amplitude was plotted against VOR gain for these 4 averages. Amplitude was greater when VOR gain was reduced, with a remarkably high correlation (R2 =0.996). These findings confirm that vestibular feedback plays an important role in the control of voluntary head movement. Furthermore, the data suggest that instability of the visual scene reported by subjects shaking their heads after TR resulted not only from a lower VOR gain, but also from the inadvertent use of higher head velocities. Show more

Keywords: head movement, vestibular, VOR, human

DOI: 10.3233/VES-1996-6507

Citation: Journal of Vestibular Research, vol. 6, no. 5, pp. 387-393, 1996