Theoretical considerations on canal-otolith interaction and an observer model.

Bos JE, Bles W.

TNO Human Factors, Soesterberg, The Netherlands. Bos tm.tno.nl

Subjective vertical orientation, eye and body movements, and motion sickness all depend on the way our central nervous system deals with the gravito-inertial force resolution problem: how to discern accelerations due to motion from those due to gravity, despite these accelerations being physically indistinguishable. To control body or eye movements, the accelerations due to motion should be known explicitly. Hence, somehow gravity should be filtered out of the specific force or gravito-inertial acceleration (GIA, the sum of both accelerations) as sensed by the otoliths, which are the linear accelerometers in the inner ear. As the GIA also changes in a head-fixed frame of reference when the head is rotated, angular motion as sensed by the semicircular canals in the inner ear should also be considered. We present here a theoretical approach to this problem, and show that the mathematical description of canal-otolith interaction is in fact a three-dimensional equivalent of the two-dimensional description given by Mayne in 1974. A simple low-pass filter is used to divide the GIA into a motion and a gravity component. The retardation of the somatogravic effect by concomitant angular motion during centrifugation is shown as a result. Furthermore we show how the canal-otolith interaction fits within the framework of an observer model to describe subjective vertical orientation, eye movement and motion sickness characteristics. To predict a frequency peak in sickness severity, for example, it is necessary to explicitly include the Mayne equation operating both on sensor afferents and in the internal model. From tilt and translation data from centrifugation and horizontal oscillation, as well as from motion sickness data, we conclude that the time constant of the low-pass filter is in the order of seconds instead of tens of seconds as assumed before. Several corollaries are additionally discussed as a result.

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Motion sickness and otolith asymmetry.

Scherer H, Helling K, Clarke AH, Hausmann S.

ENT-Clinic of the Free University of Berlin, Berlin, Germany. scherer medizin.fu-berlin.de

There is a highly scattered inter-individual susceptibility in man to motion sickness. It is discussed whether different masses of otoconias between right and left sides are responsible for a high susceptibility. In order to proof this theory, we measured the otoliths of fish (salmons, trouts, Xiphophorus Helleri; Sumatra barbes) and found big differences in the utricular stones up to 140%. The mass differences of the saccular stones were much smaller. In fish, showing abnormal swimming behavior during off-vertical axis rotation we found big mass differences compared to that of normal swimmers. This difference was only seen in the utricular and not in the saccular stones. We therefore assume, that a big mass difference is one of the factors to trigger motion sickness especially for the high susceptibility to it. The macula utriculi seem to be much more integrated in the vestibular sense than the macula sacculi.

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Predicting motion sickness during parabolic flight.

Harm DL, Schlegel TT.

Neurosciences Laboratory, NASA Johnson Space Center, Houston, TX 77058, USA. dharm ems.jsc.nasa.gov

BACKGROUND: There are large individual differences in susceptibility to motion sickness. Attempts to predict who will become motion sick have had limited success. In the present study, we examined gender differences in resting levels of salivary amylase and total protein, cardiac interbeat intervals (R-R intervals), and a sympathovagal index and evaluated their potential to correctly classify individuals into two motion sickness severity groups. METHODS: Sixteen subjects (10 men and 6 women) flew four sets of 10 parabolas aboard NASA's KC-135 aircraft. Saliva samples for amylase and total protein were collected preflight on the day of the flight and motion sickness symptoms were recorded during each parabola. Cardiovascular parameters were collected in the supine position 1-5 days before the flight. RESULTS: There were no significant gender differences in sickness severity or any of the other variables mentioned above. Discriminant analysis using salivary amylase, R-R intervals and the sympathovagal index produced a significant Wilks' lambda coefficient of 0.36, p=0.006. The analysis correctly classified 87% of the subjects into the none-mild sickness or the moderate-severe sickness group. CONCLUSIONS: The linear combination of resting levels of salivary amylase, high-frequency R-R interval levels, and a sympathovagal index may be useful in predicting motion sickness severity.

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Effect of magnitude and direction of horizontal oscillation on motion sickness.

Griffin MJ, Mills KL.

Human Factors Research Unit, Institute of Sound and Vibration Research, University of Southampton, England. M.J.Griffin soton.ac.uk

BACKGROUND: Various types of motion and visual scene can cause motion sickness, but sickness in land transport seems to be often associated with variations in horizontal acceleration. If horizontal oscillation causes sickness, it seems reasonable to assume that greater amounts of motion (i.e., an increased magnitude of motion or an increased duration of motion) will increase the extent of the sickness. HYPOTHESIS: It was hypothesized that the magnitude, direction, and duration of horizontal oscillation would affect the sickness experienced by subjects. METHOD: The 144 subjects were exposed to horizontal sinusoidal oscillation at a frequency of 0.315 Hz while seated in a closed cabin with their eyes open for up to 30 min. Subjects were exposed to one of 12 conditions with either fore-and-aft or lateral oscillation at magnitudes of either: (i) 0.28 ms(-2) rms, (ii) 0.56 ms(-2) rms, (iii) 0.70 ms(-2) rms, (iv) 0.89 ms(-2) rms, (v) 1.11 ms(-2) rms, or (vi) a stationary control condition. Subjects provided ratings of their motion sickness symptoms at 1-min intervals during the 30-min exposures. RESULTS: At a frequency of 0.315 Hz, an increase in either the magnitude or the duration of horizontal oscillation resulted in increases in the incidence of motion sickness. There were significant positive correlations between self-ratings of motion sickness susceptibility provided by subjects before participating in the experiment and their illness ratings during the experiment. CONCLUSIONS: At a frequency of 0.315 Hz, motion sickness caused by horizontal oscillation increases with increases in the magnitude and duration of horizontal oscillation. For the conditions of this study, the sickness was similar with fore-and-aft and lateral oscillation.

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Changes in gastric myoelectric activity during space flight.

Harm DL, Sandoz GR, Stern RM.

Neurosciences Laboratory, NASA Johnson Space Center, Houston, Texas 77058, USA.

The purpose of the present study was to examine postprandial myoelectric activity of the stomach and gastric activity associated with space motion sickness using electrogastrography. Three crewmembers participated in this investigation. Preflight, subjects exhibited normal postprandial responses to the ingestion of a meal. Inflight, crewmembers exhibited an abnormal decrease in the power of the normal gastric slow wave after eating on flight day 1, but had a normal postprandial response by flight day 3. Prior to and during episodes of nausea and vomiting, the electrical activity of the stomach became dysrhythmic with 60-80% of the spectral power in the bradygastric and tachygastric frequency ranges. These findings indicate that gastric motility may be decreased during the first few days of space flight. In addition, changes in the frequency of the gastric slow wave associated with space motion sickness symptoms are consistent with those reported for laboratory-induced motion sickness.

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The effect of serotonin and serotonin receptor antagonists on motion sickness in Suncus murinus.

Javid FA, Naylor RJ.

Postgraduate Studies in Pharmacology, The School of Pharmacy, University of Bradford, Bradford BD7 1DP, England, UK. fajavid1 bradford.ac.uk

In the present study, we investigated the effect of 5-hydroxytryptamine (5-HT) and 5-HT receptor agonists and antagonists on motion sickness in Suncus murinus, and the possibility that the emetic stimulus of 5-HT can alter the sensitivity of the animals to the different emetic stimulus of motion sickness. 5-HT (1.0, 2.0, 4.0 and 8.0 mg/kg ip) induced emesis and that was antagonised by methysergide (1.0 mg/kg ip), the 5-HT(4) receptor antagonist sulphamate[1-[2-[(methylsulphonyl)amino]ethyl]-4-piperidinyl]methyl-5-fluoro-2-methoxy-1H-indole-3-carboxylate (GR125487D; 1.0 mg/kg ip) and granisetron (0.5 mg/kg ip). Pretreatment with 5-HT caused a dose-related attenuation of the emetic response induced by a subsequent motion stimulus, which was not significantly modified by methysergide, granisetron or GR125487D pretreatment. (+)-1-(2,5-Dimethoxy-4-iodophenyl)-2-amino-propane (DOI; 0.5 and 1.0 mg/kg ip), 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT; 0.1 mg/kg ip) but not methysergide, GR125487D or granisetron, attenuated motion-induced emesis, and that was not affected by pretreatment with ketanserin (2.0 mg/kg, ip) or N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide trihydrocholoride (WAY-100635; 1.0 mg/kg ip), respectively. Indeed, ketanserin alone (0.1, 0.3, 1.0 and 2.0 mg/kg ip) attenuated motion sickness. These data indicate that 5-HT(1/2), 5-HT(3) and 5-HT(4) receptors are involved in the induction of 5-HT-induced emesis. However, agonist action at the 5-HT(1A/7) and 5-HT(2) receptors, and antagonist action at the 5-HT(2A) receptors can attenuate motion sickness in S. murinus.

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[Effects of motion sickness evoked by parallel swing stimulation on posture equilibrium]

[Article in Chinese]

Gu HG, Pei JC, Tong BL, Liu ZQ.

Institute of Space Medico-Engineering, Beijing, China.

Objective. To study the effects of motion sickness on posture equilibrium. Method. Dynamic posture was tested pre- and following motion sickness evoked by parallel swing. 17 healthy men were divided into motion sickness sensitive group (12) and motion sickness insensitive groups (5) according to their endurance times and the severeness of symptom. Result. The composite equilibrium score significantly decreased post-swing in all subjects. The composite equilibrium score, certain other equilibrium scores (SOT4, SOT5 and SOT6), the strategy scores (STRAT4 and STRAT6) and the sensory score (SEN3 and SEN5) significantly decreased in the sensitive group, but unchanged in the insensitive group post-swing. The equilibrium score (SOT2), and the sensory score (SEN1) pre-swing, the strategy score (STRAT3) of insensitive group is significantly higher than the sensitive group. Conclusion. Motion sickness can influence postural equilibrium. Postural instability and instability of strategy are related to the sensitiveness to motion sickness.

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[Comparison between two anti-motion sickness drugs]

[Article in Chinese]

Wang J, Qian JK, Wang BZ, Gao JY, Shi HZ.

Institute of Space Medico-Engineering, Beijing, China.

Objective. To test the validity of an animal model in selecting anti-motion sickness drugs, and compare the effects of two drugs. Method. Anti-motion sickness effects of two drugs (Cyclizine and Scopolamin-d-amphetamin compound) were observed in rats with motion sickness (MS) induced by rotatory stimulation and the amount of Kaolin ate by rats was taken as an evaluation criterion. Result. The consumption of Kaolin by the rats decreased significantly after administration of both drugs, and the effect of Scopolamin-d-amphetamin compound was better than those of Cyclizine under the same condition. Conclusion. It suggests that the rat model of motion sickness is practical and useful in studying anti-motion sickness drugs.

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