Adaptation of the vestibulo-ocular reflex, subjective tilt, and motion sickness to head movements during short-radius centrifugation.

Young LR, Sienko KH, Lyne LE, Hecht H, Natapoff A.

Man-Vehicle Lab Massachusetts Institute of Technology, Cambridge, MA 02139, USA. lry mit.edu

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 degrees 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.

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Protein-predominant meals inhibit the development of gastric tachyarrhythmia, nausea and the symptoms of motion sickness.

Levine ME, Muth ER, Williamson MJ, Stern RM.

Department of Psychology, The Pennsylvania State University, University Park, PA, USA. mlevine wfubmc.edu

BACKGROUND: Meal ingestion has been suggested to reduce susceptibility to the development of gastric tachyarrhythmia, the abnormal activity of the stomach that frequently accompanies nausea. AIM: To determine the types of meal that are most effective in preventing the development of gastric tachyarrhythmia, nausea and the symptoms of motion sickness provoked by a rotating optokinetic drum. METHOD: Participants received a carbohydrate beverage, a protein-predominant beverage or nothing immediately before exposure to the rotating drum. Subjective symptoms of motion sickness and electrogastrograms were collected during a 6-min baseline period and a subsequent 16-min drum rotation period. RESULTS: Subjective symptoms of motion sickness scores were significantly more severe during the no-meal condition than during either the protein or carbohydrate condition. Central, peripheral and, to some extent, gastrointestinal symptoms were more severe during the carbohydrate condition than during the protein condition. Gastric tachyarrhythmia increased significantly less from baseline to drum rotation during both the protein and carbohydrate conditions than during the no-meal condition. CONCLUSIONS: Liquid protein-predominant meals were most effective in suppressing both the development of gastric tachyarrhythmia and the entire spectrum of motion sickness symptoms, including nausea.

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Correlation of phasic and tonic skin-conductance responses with severity of motion sickness induced by viewing an optokinetic rotating drum.

Wan H, Hu S, Wang J.

Southern Yangtze University.

50 subjects viewed an optokinetic rotating drum for 12 min. Subjective ratings of motion sickness were obtained during the development of motion sickness. The tonic and phasic skin-conductance responses were recorded from the sites of finger, palm, and forehead during the baseline and drum-rotation periods. Analysis showed subjects' subjective ratings of motion sickness gradually increased during the 12 min. of the drum-rotation period. Both phasic and tonic skin conductance also gradually increased during drum rotation for all subjects. Pearson correlations for 50 subjects showed their ratings of motion sickness during the drum-rotation period were significantly correlated with ratios of phasic skin conductance recorded at the forehead between drum rotation and baseline periods (r = .62), followed by ratios of tonic skin conductance recorded at the finger palmar site (r = .48), ratios of phasic skin conductance recorded at the finger palmar site (r = .43), and ratios of tonic skin conductance recorded at the forehead site (r = .39). In conclusion, the phasic skin-conductance responses recorded at the forehead site were most sensitive physiological correlates of motion sickness induced by viewing an optokinetic rotating drum.

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Display color affects motion sickness symptoms in an optokinetic drum.

Bonato F, Bubka A, Alfieri L.

Department of Psychology, Saint Peter's College, Jersey City, NJ 07306, USA. Fbonato spc.edu

BACKGROUND: Many stationary participants who view the patterned interior of a rotating cylinder (optokinetic drum) experience motion sickness (MS) symptoms. Most drum interiors have consisted of black and white patterns. An experiment was conducted to investigate the effects of chromaticity on MS onset and severity. METHODS: There were 12 individuals who participated in the experiment (4 men, 8 women, mean age = 25). Keeping rotation speed constant (5 RPM), the color of vertical stripes in an optokinetic drum was manipulated. There were three conditions used: 1) alternating black and white stripes; 2) gray stripes having different luminance values; and 3) chromatic stripes (white, red, yellow, black, green, and blue) that approximately matched the luminance values of the stripes in the gray condition. Every 2 min, eight motion sickness symptoms were assessed (for up to 16 min) using a subjective scale (0 = none, 1 = slight, 2 = moderate, 3 = severe). RESULTS: Overall, MS onset was fastest, and symptoms the most severe, in the chromatic condition. The two major MS symptoms that were significantly affected were headache and dizziness. CONCLUSIONS: Chromaticity may affect how much an observer's visual environment appears to be stationary, perhaps because chromaticity is such a common feature of the stationary environment in which our visual system evolved. In an optokinetic drum, the addition of chromaticity may increase the disparity between visual and vestibular inputs, a factor thought by many to contribute to MS onset and severity.

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Vestibular suppression during space flight.

Watt D, Lefebvre L.

Aerospace Medical Research Unit, McGill University, 3655 Prom. Sir William Osler, Montreal, Quebec, Canada H3G 1Y6. doug.watt mcgill.ca

Normal movements performed while voluntarily fixing the head to the torso can lead to motion sickness in susceptible individuals. The underlying mechanism may involve excessive suppression of vestibular responses. A similar motor strategy is often adopted in the early days of a space flight and might contribute to the development of space motion sickness. In a recent experiment, we monitored the eye, head and upper torso rotations of four Life and Microgravity Spacelab crew members. For the purposes of this study, all data were excluded except for periods during which the subject was performing pure yaw-axis head movements. All subjects showed a significant increase in gaze slip on the first day of their mission, suggesting that increased vestibular suppression was occurring. Furthermore, this amount of increased suppression would have been more than adequate to produce motion sickness in susceptible individuals on the ground. The results support the theory of two, independent mechanisms for space motion sickness.

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The contribution of expectations to motion sickness symptoms and gastric activity.

Williamson MJ, Thomas MJ, Stern RM.

Department of Psychology, 535 Bruce V. Moore Building, Pennsylvania State University, University Park, PA 16802, USA.

OBJECTIVE: The goal of this investigation was to determine in healthy adults the effect of expectation manipulations on the development of motion sickness, as indicated by abnormal gastric myoelectric activity and subjective reports of symptoms of motion sickness. METHOD: Eighty participants, moderately susceptible to motion sickness, experienced one of four conditions created from a two-variable (Expectation, Drum), two-factor model (High/Low expectation for sickness; Rotating/Stable Drum). The electrogastrogram (EGG) was recorded 6 min prior to the expectation manipulation; 6 min following the expectation manipulation; 6 min before drum activation; and 16 min during drum activation. Self-report questionnaires indicating expectation for sickness (MSEx) and motion sickness symptoms (Nausea Profile [NP]) were obtained following the expectation manipulation and exposure to the drum, respectively. RESULTS: No significant differences were observed among expectation groups for retrospective reports of motion sickness (NP); however, significant differences in EGG responses to drum rotation were obtained. The unexpected results of a univariate analysis of variance (ANOVA) revealed significantly greater gastric tachyarrhythmia and less normal activity, an indication of motion sickness, in the low expectation for sickness conditions. CONCLUSION: These results suggest that inducing a high expectation for sickness in healthy individuals about to be exposed to provocative motion results in a protective effect from motion sickness following exposure to the stimulus, while low expectations may induce abnormal gastric activity. Copyright 2004 Elsevier Inc.

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Effects of intestinal electrical stimulation on intestinal dysrhythmia and symptoms in dogs.

Liu J, Wang L, Chen JD.

Division of Gastroenterology, University of Texas Medical Branch, Galveston, Texas 77555-0632, USA.

The aim of this study was to investigate the effect of intestinal electrical stimulation on small intestinal dysrhythmia and motion sickness-like symptoms induced by vasopressin. Female dogs chronically implanted with two pairs of electrodes on jejunum serosa were used in a four-session study. Saline and vasopressin were infused in sessions 1 and 2, respectively. Sessions 3 and 4 were the same as session 2, except a long- or short-pulse intestinal electrical stimulation was applied on the proximal pair of electrodes. Intestinal slow waves and motion sickness-like symptoms were recorded in each session. Results were as follows. (1) Vasopressin induced intestinal dysrhythmia, uncoupling of slow waves, and vomiting and motion sickness-like symptoms (P < 0.05, ANOVA). (2) Intestinal electrical stimulation with long pulses, but not short pulses, was capable of preventing vasopressin-induced intestinal dysrhythmia. (3) Intestinal electrical stimulation with short pulses, but not long pulses, prevented vomiting and the motion sickness-like symptoms. It is concluded that vasopressin induces intestinal dysrhythmia. Long-pulse intestinal stimulation normalizes vasopressin-induced intestinal slow-wave abnormalities with no improvement in symptoms. Short-pulse stimulation prevents emetic symptoms induced by vasopressin but has no effect on slow waves. These data suggest different mechanisms involved with different methods of intestinal stimulation.

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Motion sickness in public road transport: the effect of driver, route and vehicle.

Turner M, Griffin MJ.

Institute of Sound and Vibration Research, University of Southampton, UK.

Relationships between vehicle motion and passenger sickness have been investigated in a survey of 3256 passengers travelling on 56 mainland UK bus or coach journeys. Vehicle motion was measured throughout all journeys, yielding over 110 h of six-axis coach motion data from five types of coach and 17 different drivers. Overall, 28.4% of passengers reported feelings of illness, 12.8% reported nausea and 1.7% reported vomiting during coach travel. Passenger nausea and illness ratings increased with increased exposure to lateral coach motion at low frequencies (< 0.5 Hz). Motion in other axes correlated less well with sickness, although there were some intercorrelations between the motions in the different axes. Sickness levels among passengers were greater with drivers who drove to produce higher average magnitudes of fore-and-aft and lateral vehicle motion. Nausea occurrence was greater on routes classified as being predominantly cross-country where magnitudes of lateral vehicle motion were significantly higher. Lateral motion and motion sickness increased from the front to the rear of each vehicle. No significant differences in sickness were found between the five different vehicle types used in the study. The applicability of a motion sickness dose model to these data is discussed.

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