[Specific features of the motor function of the digestive organs in persons with different degree of resistance to motion sickness]

[Article in Russian]

Afonin BV, Rogov VA, Ruvinova LG, Poliakov BI, Inozemtsev SL.

The effect of three exposures to Coriolis acceleration on the frequency and amplitude of fasting stomach contractions was investigated in 6 resistant and 16 susceptible to motion sickness test subjects. After tests all of them underwent gastroduodenoscopy and 4 subjects from each group were subjected to echography to measure gall bladder contractility in response to glucose-milk loads. After tests the motor activity of the stomach increased slightly in resistant subjects due to an increase of the amplitude and a slight decrease of biopotential frequency. During gastroscopy antral and pyloric sphincters were closed. In the stomach there was an insignificant amount of contents without gall. In the susceptible group, the motor activity was, on the contrary, inhibited due to a significant decline of the wave amplitude and frequency (by 40% and 11%, respectively). In the stomach, one or both sphincters were widely open; it also contained a large amount of gastric juice and gall. In 36% of susceptible and 17% resistant subjects, diaphragmatic hernia (at the esophageal opening) was found. Ultrasonic examination of the gall bladder showed that susceptible subjects developed its faster and stronger contraction when compared to resistant subject in response to glucose-milk loading. This pointed to a more prolonged duration of the gall excretion phase. Reactive changes of the gastroduodenal zone in response to motion tests facilitated duodenal-gastric reflux and major gastrointestinal symptoms of motion sickness.

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Effects of vection-induced motion sickness on gastric myoelectric activity and oral-cecal transit time.

Muth ER, Stern RM, Koch KL.

Department of Psychology, Pennsylvania State University, University Park, USA.

The purpose of this study was to investigate the effects of vection-induced motion sickness on three cycle per minute gastric myoelectric activity and oral-cecal transit time. Forty-five subjects were exposed to a rotating optokinetic drum while electrogastrograms and subjective reports of symptoms were monitored. Prior to exposure, baseline breath hydrogen levels were established and subjects ingested vanilla pudding containing 10 g of lactulose. Breath hydrogen measurements were obtained before drum rotation and every 10 minutes after rotation, for 3 hr. Based on the severity of motion sickness symptoms reported, subjects were divided into two groups: a group susceptible to, and a group not susceptible to, vection-induced motion sickness. Averaged across subjects, the percentage of three cycle per minute activity decreased from baseline to rotation (3.6%) and from rotation to recovery (3.0%) [F(2/70)=2.43,P<0.1], with the susceptible group showing a greater overall decrease from baseline to recovery (8.9%), than the nonsusceptible group (4.2%) [F(1/35)=11.16,P<0.01]. The susceptible group had longer average oral-cecal transit times (144 min) than the nonsusceptible group (107 min) [t(36)=3.27,P<0.01]. Furthermore, symptom reports were positively correlated with oral-cecal transit times (r = 0.43, P < 0.05). In conclusion, vection-induced motion sickness is accompanied by decreased gastric three cycle per minute activity and prolonged oral-cecal transit times.

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Changes in the gastrointestinal electric pattern to motion sickness in susceptibles and insusceptibles during fasting.

Kolev OI, Altaparmakov IA.

Section of Otoneurology, University Hospital of Neurology and Psychiatry, Sofia, Bulgaria.

The cardinal symptoms of motion sickness occur in the gastrointestinal system. This study sought to investigate the influence of sickness-provoking motion stimuli on the interdigestive migrating electric complex (IDMEC) of the gastro-intestinal system. Thirteen susceptibles and 14 insusceptibles to motion sickness were subjected to intralumenal recording before and after caloric vestibular stimulations. Motion sickness developed in all subjects. The results indicate that there are no significant differences in the IDMECs of susceptibles and insusceptibles in a state of rest; vestibular stimulation changes the duration of IDMEC phases (P < 0.05 and P < 0.01); IDMEC changes differ slightly between susceptibles and insusceptibles; motion stimuli induce simultaneous nonpropulsive spike activity, which is more frequent in susceptibles (P < 0.01); vestibular stimulation applied during phase III of IDMEC does not provoke vomiting in susceptibles.

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Motion sickness potentiates core cooling during immersion in humans.

Mekjavic IB, Tipton MJ, Gennser M, Eiken O.

Institute of Biomedical & Biomolecular Sciences, Department of Sports and Exercise Science, University of Portsmouth, Portsmouth, Hampshire PO1 2DT, UK. igor.mekjavic ijs.si

1. The present study tested the hypothesis that motion sickness affects thermoregulatory responses to cooling in humans. 2. Ten healthy male volunteers underwent three separate head-out immersions in 28 degrees C water after different preparatory procedures. In the 'control' procedure immersion was preceded by a rest period. In the 'motion sickness' procedure immersion was preceded by provocation of motion sickness in a human centrifuge. This comprised rapid and repeated alterations of the gravitational (G-) stress in the head-to-foot direction, plus a standardized regimen of head movements at increased G-stress. In the 'G-control' procedure, the subjects were exposed to similar G-stress, but without the motion sickness provocation. 3. During immersion mean skin temperature, rectal temperature, the difference in temperature between the forearm and 3rd digit of the right hand (DeltaT(forearm-fingertip)), oxygen uptake and heart rate were recorded. Subjects provided ratings of temperature perception, thermal comfort and level of motion sickness discomfort at regular intervals. 4. No differences were observed in any of the variables between control and G-control procedures. In the motion sickness procedure, the DeltaT(forearm-fingertip) response was significantly attenuated, indicating a blunted vasoconstrictor response, and rectal temperature decreased at a faster rate. No other differences were observed. 5. Motion sickness attenuates the vasoconstrictor response to skin and core cooling, thereby enhancing heat loss and the magnitude of the fall in deep body temperature. Motion sickness may predispose individuals to hypothermia, and have significant implications for survival time in maritime accidents.

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Motion sickness during off-vertical axis rotation: prediction by a model of sensory interactions and correlation with other forms of motion sickness.

Denise P, Etard O, Zupan L, Darlot C.

Laboratoire de Physiologie, Faculte de Medecine, Caen Cedex, France.

Motion sickness (MS) susceptibility of 108 normal subjects was measured during off-vertical axis rotation (OVAR) as a function of angular velocity (60-180 degrees/s). The chair rotated about a longitudinal axis tilted 30 degrees with respect to gravity. For each velocity, we measured the duration of exposure necessary to evoke a moderate malaise, with a limit of 30 min. MS appeared the fastest at a rotation velocity of 105 degrees/s; higher or lower velocities were less provocative. These results are in good agreement with predictions made by Zupan et al. [in ICANN'94, Springer-Verlag, 1995] by means of a MS mathematical model derived from a model of sensory interactions [Droulez and Darlot, in Attention and Performance, Vol. 13, Lawrence Erlbaum, Hillsdale, 1989]. We also found that MS susceptibility during OVAR is positively correlated with susceptibility to other forms of MS. Since OVAR induces sensory messages very different from those induced by other provocative stimulations, this could suggest that the sensitivity of a common final vegetative locus is an important factor of the individual differences in susceptibility to MS.

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Optokinetic rotation-induced taste aversions correlate with over-all symptoms of motion sickness in humans.

Hu S, Willoughby LM, Lagomarsino JJ, Jaeger HA.

Department of Psychology, Humboldt State University, Arcata, CA 95521, USA. husenqi axe.humboldt.edu

51 subjects were divided into Familiar- and Unfamiliar-drink groups based on whether they had tasted soybean milk before the experiment. Each subject then viewed an optokinetic rotating drum for 10 min. Subjective assessments of nausea and over-all symptoms of motion sickness were measured during the drum rotation. Two hours later subjects drank the soybean milk again. The consumed volume and rating of likeableness of the drink were subsequently measured. Analysis showed that the subjects in the Unfamiliar-drink group reported significantly higher taste aversion and consumed significantly less soybean milk after rotation than those in the Familiar-drink group. Correlation for the Unfamiliar-drink group indicated that the rated taste aversion was positively correlated with ratings of over-all symptoms of motion sickness and that the consumed volume of soybean milk was negatively correlated with ratings of over-all symptoms of motion sickness. We concluded that the magnitude of acquired conditioned taste aversion was dependent upon the severity of over-all symptoms of visually induced motion sickness when subjects were unfamiliar with the flavor of the target drink.

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Asian hypersusceptibility to motion sickness.

Stern RM, Hu S, Uijtdehaage SH, Muth ER, Xu LH, Koch KL.

Department of Psychology, Pennsylvania State University, University Park, USA.

A rotating optokinetic drum was used in three laboratory studies to test the hypothesis that Asian subjects are hypersusceptible to motion sickness. The results of the first study showed that Chinese women compared to European-American and African-American women experienced significantly more severe symptoms of motion sickness and greater disturbance of normal gastric myoelectric activity. A second study yielded similar results using American-born children of Asian parents. The results of a third study using Chinese men and women were similar and showed a significant increase in vasopressin during rotation. Possible genetic mechanisms that may account for these results are discussed.

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Vestibular factors influencing the biomedical support of humans in space.

Lichtenberg BK.

Payload Systems Inc., Wellesley, MA 02181.

This paper will describe the biomedical support aspects of humans in space with respect to the vestibular system. The vestibular system is thought to be the primary sensory system involved in the short-term effects of space motion sickness although there is increasing evidence that many factors play a role in this complex set of symptoms. There is the possibility that an individual's inner sense of orientation may be strongly coupled with the susceptibility to space motion sickness. A variety of suggested countermeasures for space motion sickness will be described. Although there are no known ground-based tests that can predict space motion sickness, the search should go on. The long term effects of the vestibular system in weightlessness are still relatively unknown. Some preliminary data has shown that the otoconia are irregular in size and distribution following extended periods of weightlessness. The ramifications of this data are not yet known and because the data was obtained on lower order animals, definitive studies and results must wait until the space station era when higher primates can be studied for long durations. This leads us to artificial gravity, the last topic of this paper. The vestibular system is intimately tied to this question since it has been shown on Earth that exposure to a slow rotating room causes motion sickness for some period of time before adaptation occurs. If the artificial gravity is intermittent, will this mean that people will get sick every time they experience it? The data from many astronauts returning to Earth indicates that a variety of sensory illusions are present, especially immediately upon return to a 1-g environment. Oscillopsia or apparent motion of the visual surround upon head motion along with inappropriate eye motions for a given head motion, all indicate that there is much to be studied yet about the vestibular and CNS systems reaction to a sudden application of a steady state acceleration field like 1-g. From the above information it is obvious that the vestibular system does have unique requirements when it comes to the biomedical support of space flight. This is not to say that other areas such as cardiovascular, musculo-skeletal, immunological and hematological systems do not have their own unique requirements but that possible solutions to one system can provide continuing problems to another system. For example, artificial gravity might be helpful for long term stabilization of bone demineralization or cardiovascular deconditioning but might introduce a new set of problems in orientation, vestibular conflict and just plain body motion in a rotating space vehicle.

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