Sudden emesis following parabolic flight maneuvers: implications for space motion sickness.

Lackner JR, Graybiel A.

Episodes of emesis unaccompanied by the usual prodromal signs of motion sickness have been reported by astronauts in the space shuttle program (10). Such reports have raised the issue whether space motion sickness has different characteristics from terrestrial motion sickness. We present evidence here from parabolic flight experiments that sudden vomiting can occur in response to a provocative vestibular stimulus even when no premonitory symptoms are being experienced. Accordingly, in chronic exposure conditions, the absence of prominent signs or symptoms of motion sickness does not necessarily mean an absence of sensitization.

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[Use of central electroanalgesia to restore the body's functional state in motion sickness]

[Article in Russian]

Nekhaev AS, Vlasov VD, Ivanov VV.

Central electroanalgesia (CEAN) is a technique that involves application of pulsating current to the central nervous system in order to enhance its tonicity recover autonomic equilibrium and to reduce parasympathetic cardiovascular reactions. In two experimental runs in which 9 volunteers participated the efficacy of CEAN in preventing motion sickness symptoms produced by Markaryan's test was studied. After two rotations repeated with a one-hour interval vestibular reactions persisted for 7-10 hours. CEAN had a positive effect: after a one-hour CEAN session applied between two rotations the tolerance time of the second rotation increased on an average by 76%. An additional exposure to CEAN after rotation eliminated almost completely the adverse effects of rotation and made effective the postrotation work. Due to CEAN parasympathetic reactions of the cardiovascular system typical of the postrotation recovery period were indistinct. These data suggest that CEAN is an effective method to be used to help a rapid recovery of the functional state of the human body during motion sickness.

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[These vestibular problems in the absence of gravity...]

[Article in French]

Timsit C.

For a few years, more and more astronauts complain to endure space motion sickness during the two or three first days of their mission. This is due to the repetition of shifting and sudden head movements, which becomes possible by the increasing of volume of the new space stations. To avoid that payload specialists onboard be obliged to renounce to conduct planned experiments, it has been necessary to find effective solutions to detect by ground based tests the candidates sensitive to space motion sickness and perfect therapeutic means able to avoid unexpected arrival of these symptoms, and even to treat them. The best results are undeniably obtained by the "Biofeedback" and the "tolerance" training, but we base wide hopes on ginger roots and on tolerance with sensorial deprivation lockers. However, we must not disregard the trigger action of emotional factors and anxiety in space motion sickness. The European mission SPACELAB-1 has been marked by the display of a caloric nystagmus during the vestibular experiments in weightlessness. If no explanation is given to this phenomenon, it will be necessary to call in question the role of the thermal convection described by Barany in the appearance of the caloric nystagmus.

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M.I.T./Canadian vestibular experiments on the Spacelab-1 mission: 1. Sensory adaptation to weightlessness and readaptation to one-g: an overview.

Young LR, Oman CM, Watt DG, Money KE, Lichtenberg BK, Kenyon RV, Arrott AP.

Experiments on human spatial orientation were conducted on four crewmembers of Space Shuttle Spacelab Mission 1. This introductory paper presents the conceptual background of the project, the relationship among the experiments and their relevance to a "sensory reinterpretation hypothesis". Detailed experiment procedures and results are presented in the accompanying papers in this series. The overall findings are discussed in this article as they pertain to the following aspects of hypothesized sensory reinterpretation in weightlessness: utricular otolith afferent signals are reinterpreted as indicating head translation rather than tilt, sensitivity of reflex responses to footward acceleration is reduced, and increased weighting is given to visual and tactile cues in orientation perception and posture control. Three subjects developed space motion sickness symptoms, which abated after several days. Head movements, as well as visual and tactile cues to orientation influenced symptoms in a manner consistent with the sensory-motor conflict theory of space motion sickness. Six short duration tests of motion sickness susceptibility, conducted pre-flight, failed to predict sickness intensity in weightlessness. An early otolith-spinal reflex, measured by electromyography from the gastrocnemius-soleus muscles during sudden footward acceleration, was inhibited immediately upon entering weightlessness and declined further during the flight, but was unchanged from pre-flight when measured shortly after return to earth. Dynamic visual-vestibular interaction was studied by measuring subjective roll self-motion created by looking into a spinning drum. Results suggest increased weighting of visual cues and reduced weighting of graviceptor signals in weightlessness. Following the 10 day flight, erect posture with eyes closed was disturbed for several days.(ABSTRACT TRUNCATED AT 250 WORDS)

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Comparative assessment of vestibular, optokinetic, and optovestibular stimulation in the development of experimental motion sickness.

Matsnev EI, Kuz'min MP, Zakharova LN.

Institute of Biomedical Problems, Moscow, USSR.

The contribution of vestibular, optokinetic, and optovestibular stimulation to experimental motion sickness was evaluated in 29 volunteer subjects. Vestibular stimulation (Coriolis effect) was found to induce the most significant vestibular-autonomic disorders. Optokinetic stimulation (pseudo-Coriolis effect) and optovestibular stimulation could provoke such disorders only in susceptible subjects. In quantitative terms, optokinetic and optovestibular stimulation were less effective than vestibular Coriolis stress. Nystagmic reactions of susceptible subjects to the three types of stimulation differed significantly from those of tolerant subjects. This may be important from the theoretical point of view because susceptibility to motion sickness and responses to vestibular and optokinetic stimulation may be universal and associated with the general CNS mechanism, i.e. inhibition mechanism. The identified correlation between the duration of postoptokinetic illusion and motion sickness susceptibility may be used to differentiate susceptible and tolerant subjects.

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Clinical characterization and etiology of space motion sickness.

Thornton WE, Moore TP, Pool SL, Vanderploeg J.

Astronaut Office, NASA/Johnson Space Center, Houston, Texas 77058.

An inflight, clinically-oriented investigation of SMS was begun on STS-4 and revealed the following: compared to motion sickness on Earth, autonomic signs are significantly different in space motion sickness (SMS) vs. motion sickness (MS) in that sweating is not present, pallor or flushing may be present, and vomiting is episodic, sudden, and brief. Nausea may be present but is more often absent. Onset ranges from minutes to hours, plateaus, and rapidly resolves in 8-72 h with 36 h as average. Postflight reactions have been mild unless deliberately provoked in the early period of re-exposure to gravity. Postflight there is a period of resistance to all forms of motion sickness. There is some evidence for individual reduction in sensitivity on repeated flights. Etiology could not be proven objectively; however, the sensitivity to angular motion, often pronounced in pitch, and theoretical considerations make an intravestibular conflict the most likely cause. Electro-oculogram (EOG), audio-evoked potentials, measurement of fluid shifts, and other studies are inconsistent with a transient vestibular hydrops or increased intracranial pressure as a cause.

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A two-factor model of rotation-induced motion sickness syndrome in squirrel monkeys.

Wilpizeski CR, Lowry LD.

Nonrestrained squirrel monkeys were rotated repeatedly in the horizontal plane once per day for preset times or until a vomiting response occurred. Emesis latencies and frequencies were recorded. Some subjects were fed fresh banana immediately before and after each rotation. The amount consumed provided a measure of conditioned food aversion or feeding suppression. A two-factor model of the motion-sickness syndrome was formulated to account for the data. According to the model, appropriate stimulation of the semicircular canals accompanied by visual and proprioceptive stimulation generates two independent physiologic processes or states: an objective emesis and a subjective nausea process. The emesis process is revealed by vomiting responses and the nausea process is inferred from the appearance of conditioned food aversion. Susceptible monkeys (type I) and resistant monkeys (type II) have different emesis processes, but both have similar nausea processes. Refractory monkeys have no well-developed emesis or nausea processes. Time and order characteristics of the motion-sickness syndrome depend on specific interactions of emesis and nausea processes.

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Electrodermal activity as an index of motion sickness.

Warwick-Evans LA, Church RE, Hancock C, Jochim D, Morris PH, Ward F.

Sweating in the absence of thermal stimulation is one of the cardinal symptoms of motion sickness. But since sweating is closely related to electrodermal activity this may be a potentially useful index of the intensity of motion sickness. In order to evaluate this possibility, the correlations between electrodermal activity and a range of signs and symptoms of motion sickness were examined in four experiments, in which a total of 170 subjects were exposed to a cross-coupled force environment. Although increases in skin conductance did not correlate with specific single indices of motion sickness, correlations with a questionnaire based on several signs and symptoms varied from 0.89 (p less than 0.001) to 0.11 (N.S.). It is concluded that skin conductance potentially offers a valid and very precise measure of motion sickness, but that it is sensitive to extraneous factors only some of which are currently understood.

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