Spacelab experiments on space motion sickness.

Oman CM.

Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge 02139, USA.

Recent research results from ground and flight experiments on motion sickness and space sickness conducted by the Man Vehicle Laboratory are reviewed. New tools developed include a mathematical model for motion sickness, a method for quantitative measurements of skin pallor and blush in ambulatory subjects, and a magnitude estimation technique for ratio scaling of nausea or discomfort. These have been used to experimentally study the time course of skin pallor and subjective symptoms in laboratory motion sickness. In prolonged sickness, subjects become hypersensitive to nauseogenic stimuli. Results of a Spacelab-1 flight experiment are described in which four observers documented the stimulus factors for and the symptoms/signs of space sickness. The clinical character of space sickness differs somewhat from acute laboratory motion sickness. However SL-1 findings support the view that space sickness is fundamentally a motion sickness. Symptoms were subjectively alleviated by head movement restriction, maintenance of a familiar orientation with respect to the visual environment, and wedging between or strapping onto surfaces which provided broad contact cues confirming the absence of body motion.

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Reliability of provocative tests of motion sickness susceptibility.

Calkins DS, Reschke MF, Kennedy RS, Dunlop WP.

Space Biomedical Research Institute, NASA/Johnson Space Center, Houston, TX 77058.

Accurate prediction of space motion sickness is dependent, in part, upon the reliability of terrestrial-based motion sickness susceptibility tests. In the present study, test-retest reliability values were derived from motion sickness susceptibility scores obtained from two successive exposures to each of three tests: 1) Coriolis Sickness Sensitivity Index (CSSI); 2) Staircase Velocity Movement Test (SVMT); and 3) Parabolic Flight Static Chair Test (PSCT). The reliability of the three tests ranged from 0.70 to 0.88. Normalizing values from predictors with skewed distributions improved the reliability. The apparent inconsistency between our finding of high reliability of predictive tests, and previous reports of low correlations between ground-based predictors and space motion sickness may be due to unreliability in assessment of the sickness criterion. Issues of reliability and validity of predictor and criterion measures, and their implications for future development of ground-based predictive tests are discussed in some detail.

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The use of the logistic model in space motion sickness prediction.

Lin KK, Reschke MF.

Krug International, Houston, TX 77058.

The one-equation and the two-equation logistic models were used to predict tested subjects' susceptibility to motion sickness in KC-135 parabolic flights using data from other ground-based motion sickness tests. A data set containing data from 6 provocative tests, 2 vestibular function tests, and 1 motion sickness experience questionnaire from 162 subjects was used in this study. The prediction results from the logistic models were compared with those from the previously-used Bayes linear discriminant analysis procedures. The results based on this data set show that the logistic models correctly predicted substantially more cases (an average of 13%) in the data subset used for model building. In the data subset used for model cross-validation, the logistic models correctly predicted 4% and 5% more cases in the prediction of vomit or nonvomit, and of degree of susceptibility, respectively. Overall, the logistic models ranged from 53 to 65% predictions of the three endpoint parameters, whereas the Bayes linear discriminant procedure ranged from 48 to 65% correct for the cross validation sample.

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Mechanisms of selective attention and space motion sickness.

Kohl RL.

Division of Space Medicine, NASA-Johnson Space Center, Houston, TX 77058.

The neural mismatch theory of space motion sickness asserts that the central and peripheral autonomic sequelae of discordant sensory input arise from central integrative processes falling to reconcile patterns of incoming sensory information with existing memory. Stated differently, perceived novelty reaches a stress level as integrative mechanisms fail to return a sense of control to the individual in the new environment. Based on evidence summarized here, the severity of the neural mismatch may be dependent upon the relative amount of attention selectively afforded to each sensory input competing for control of behavior. Components of the limbic system may play important roles in match-mismatch operations, be therapeutically modulated by antimotion sickness drugs, and be optimally positioned to control autonomic output.

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Head movements in non-terrestrial force environments elicit motion sickness: implications for the etiology of space motion sickness.

Lackner JR, Graybiel A.

Space motion sickness has become an operational concern in manned space flight. Considerable evidence exists that head movements in free fall, especially pitch movements, are provocative until adaptation occurs (3,4,8,9,11,17,18,22,26). The question arises whether space motion sickness is an unique nosological entity or is due to body movements in a nonterrestrial force environment, a force environment for which the body's dynamic sensory-motor adaptions to 1 G are no longer appropriate (14,16,18-21). To evaluate this issue, we had subjects make controlled head movements during exposure to high gravitoinertial force levels, 1.8-2.0 G, in parabolic flight maneuvers. Head movements in pitch with eyes open were most evocative of motion sickness, yaw movements with eyes covered were least provocative. This pattern is identical to that which occurs when the same types of head movements are made in the free fall phase of parabolic maneuvers (17,18). It appears that space motion sickness is the consequence of prolonged exposure to a non-terrestrial force background rather than of exposure to free fall per se.

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Motion sickness reflex arc bypasses the area postrema in cats.

Borison HL, Borison R.

Motion-induced vomiting was studied in cats exposed to vertical sinusoidal oscillation on a spring-suspended platform. Two groups of five cats each, namely, motion-untested and motion sickness-susceptible, were subjected to chronic ablation of the area postrema. Motion sickness occurred postoperatively in all the previously untested cats, and in four of the five previously susceptible cats. Statistical comparison with normal cats indicated that the operated cats were significantly more susceptible to motion sickness. The manifest loss of susceptibility in one cat with a lesion is attributed to excessive peripostremal damage. It is concluded from these results that the area postrema is not an essential link in the reflex arc of motion-induced vomiting.

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Histaminergic mechanism of motion sickness. Neurochemical and neuropharmacological studies in rats.

Takeda N, Morita M, Kubo T, Yamatodani A, Watanabe T, Wada H, Matsunaga T.

Rats were rotated about two parallel axes to produce motion sickness, and the histamine levels in their hypothalamus and pons-medulla oblongata were measured. Rotation for 60 min induced kaolin intake, which is a behavioral index of motion sickness in rats, and increased the histamine levels in the hypothalamus and pons-medulla oblongata, the highest levels occurring after 15 min of rotation. In bilaterally labyrinthectomized rats, no rise in histamine level was observed. alpha-Fluoromethylhistidine (alpha-FMH), which depletes the neural component of histamine in the brain, suppressed kaolin intake induced by rotation. These findings demonstrated that the histaminergic neuron system contributes to development of motion sickness, and suggested that alpha-FMH may be effective as an anti-motion sickness drug.

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Torsional vestibulo-ocular reflex measurements for identifying otolith asymmetries possibly related to space motion sickness susceptibility.

Peterka RJ.

Good Samaritan Hospital & Medical Center, Clinical Vestibular Laboratory, Portland, OR 97210, USA.

Recent studies by Diamond and Markham have identified significant correlations between space motion sickness susceptibility and measures of disconjugate torsional eye movements recorded during parabolic flights. These results support an earlier proposal by von Baumgarten and Thumler which hypothesized that an asymmetry of otolith function between the two ears is the cause of space motion sickness. It may be possible to devise experiments that can be performed in the 1 g environment on earth that could identify and quantify the presence of asymmetric otolith function. This paper summarizes the known physiological and anatomical properties of the otolith organs and the properties of the torsional vestibulo-ocular reflex which are relevant to the design of a stimulus to identify otolith asymmetries. A specific stimulus which takes advantage of these properties is proposed.

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