Altered sensory-motor control of the head as an etiological factor in space-motion sickness.

Lackner JR, DiZio P.

Ashton Graybiel Spatial Orientation Laboratory, Brandeis University, Waltham, Massachusetts 02254.

Mechanical unloading during head movements in weightlessness may be an etiological factor in space-motion sickness. We simulated altered head loading on Earth without affecting vestibular stimulation by having subjects wear a weighted helmet. Eight subjects were exposed to constant velocity rotation about a vertical axis with direction reversals every 60 sec. for eight reversals with the head loaded and eight with the head unloaded. The severity of motion sickness elicited was significantly higher when the head was loaded. This suggests that altered sensory-motor control of the head is also an etiological factor in space-motion sickness.

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Adaptation to vection-induced symptoms of motion sickness.

Stern RM, Hu SQ, Vasey MW, Koch KL.

Department of Psychology, Pennsylvania State University, University Park, PA 16802.

The visual-vestibular-proprioceptive sensory mismatch of vection provokes motion sickness in approximately 60% of healthy subjects. Approximately 60% of astronauts experience motion sickness in microgravity where vestibular/otolith function is altered. The purpose of this study was to determine the extent to which symptoms of motion sickness and tachygastria, an abnormal 4-9 cpm rhythm of the stomach, decrease or adapt during three repeated exposures to a rotating circular vection drum. Subjects sat in the drum for 45 min: 15 min baseline, 15 min drum rotation at 60 degrees.s-1, and 15 min recovery. Gastric myoelectric activity was continuously recorded with the electrogastrogram (EGG). Symptom reports were obtained during rotation. In Experiment I, 10 subjects were exposed to the drum 3 times with intersession intervals of 4-24 d. They failed to show adaptation based on subjective reports and all showed tachygastria. In Experiment II, 14 new subjects were exposed to the drum 3 times with intersession intervals of 48 h. The group experienced a reduction in symptoms and tachygastria with repeated exposure to the drum. Thus, symptomatic and physiological improvement occurred after training in subjects susceptible to vection-induced motion sickness. Preflight adaptation to visual-vestibular sensory mismatch may reduce motion sickness experienced in the environment of microgravity.

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Reduction of visually-induced motion sickness elicited by changes in illumination wavelength.

Dobie TG, May JG, Dunlap WP, Anderson ME.

Naval Biodynamics Laboratory, University of New Orleans, LA 70189-0407.

This experiment was undertaken to assess the degree of stimulus generalization in visually-induced motion sickness. Sixteen subjects participated in six sessions in which they were exposed to a rotating field of vertical stripes for five 4-min trials. This stimulus elicited the perception of self-vection. In the first three sessions, the stripes were illuminated by one monochromatic light (red or green) and in the last three sessions, the stripes were illuminated by the other monochromatic light. Magnitude estimates of motion sickness increased significantly within sessions, but the rate at which this measure increased was significantly diminished across trials in the last three-session block. Magnitude estimates of vection increased within sessions and decreased across sessions, but did not increase with color change. These results can be explained in terms of a model of stimulus generalization and have implications for the reduction of motion sickness in applied settings.

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Performance and well-being under tilting conditions: the effects of visual reference and artificial horizon.

Rolnick A, Bles W.

Motion Sickness and Human Performance Laboratory, Israeli Naval Hyperbaric Institute, Haifa.

It is generally agreed that the incidence of motion sickness in sailors working below deck is higher than in sailors who have the horizon as a visual reference on the bridge. This study investigated the possible beneficial effect of a projected artificial horizon as a means to prevent seasickness. Twelve subjects were exposed to angular motion in a tilting room under three experimental conditions: a) With the windows covered, allowing no visual reference from the outside world; b) With the windows uncovered, thus allowing a partial view of the environment; and c) With the windows covered and a horizon projected on the walls by a rotating laser beam. Subjects were exposed for 35 min in each condition while performing different computerised tasks. There was a reduction in well-being and performance as a function of exposure time. These effects were clearly shown in the "closed cabin" condition. There were less motion sickness symptoms in the "artificial horizon" and "window" conditions. The presence of a visual reference prevented the decrement in performance found in the "closed cabin" condition. The results of this study suggest that a projected horizon might alleviate motion sickness aboard naval vessels, and thus improve the performance of sailors at sea.

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Role of the area postrema in three putative measures of motion sickness in the rat.

Sutton RL, Fox RA, Daunton NG.

Department of Psychology, San Jose State University, California 95192.

After thermal cauterization of the area postrema in rats the absence of conditioned taste aversion to sucrose paired with lithium chloride (0.15 M, 3.3 ml/kg) was used as a pharmacologic/behavioral index of area postrema damage. In a subsequent experiment the effects of area postrema lesions on three measures proposed as species-relevant measures of motion sickness were studied, using off-vertical rotation at 150 degrees/s for either 30 or 90 min. Lesions of area postrema did not alter postrotational suppression of drinking or amount of defecation during motion. The initial acquisition of conditioned taste aversion to a novel cider vinegar solution paired with motion was not affected by lesioning of the area postrema, but these taste aversions extinguished more slowly in lesioned rats than in sham-operates or intact controls. Results are discussed in terms of proposed humoral factors which may induce motion sickness and in light of recent data on the role of the area postrema in similar measures in species possessing the complete emetic reflex.

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A comparison of two methods of training resistance to visually-induced motion sickness.

Dobie TG, May JG, Fischer WD, Elder ST, Kubitz KA.

Motion Sciences Department, Naval Biodynamics Laboratory, New Orleans, LA 70189-0407.

This report concerns the use of two methods of training subjects to tolerate visually-induced motion sickness (VMS). Sixteen subjects were selected on the basis of their response to a motion sickness history questionnaire and assigned to one of four groups on the basis of their ability to tolerate visually-induced motion (VM). One group received 10 sessions of confidence building and desensitization training (BT); a second group received 10 sessions of EMG and temperature biofeedback (FB); a third group received 10 sessions of BT and 10 sessions of FB (BTFB); and a fourth group received no treatment (C). The results indicated that the BT and BTFB groups exhibited significant increases in tolerance to VM when pretreatment measures were compared to posttreatment measures, while no significant differences in pre-post measures were observed in the FB or C groups. A similar pattern emerged from the symptomatology data.

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Suncus murinus as a new experimental model for motion sickness.

Ueno S, Matsuki N, Saito H.

Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.

Characteristics of motion sickness and effects of possible prophylactic drugs were studied using Suncus murinus (house musk shrew) for its potential use as an experimental model in motion sickness. Mild reciprocal shaking (amplitude: 10-40 mm; frequency: 0.5-3.0 Hz) induced vomiting in most of Suncus murinus within 2 min. Adaptation was observed when the motion stimulus was repeated with an interval of 2 to 3 days. During the repetitive motion training, both the ratio of sensitive animals and the number of vomiting episodes decreased, and the time from the start of shaking to the first vomiting was extended. Subcutaneous injection of scopolamine (100 mg/kg), chlorpromazine (8 mg/kg), promethazine (50 mg/kg), diphenhydramine (20 mg/kg), chlorphenylamine (20 mg/kg) and methamphetamine (2 mg/kg) decreased the emetic effect of motion sickness, but pyrilamine (20 mg/kg), meclizine (20 mg/kg) and dimenhydrinate (32 mg/kg) were not effective or very weak. These results indicate that the Suncus murinus is sensitive to the motion stimulus and antiemetic drugs are effective as prophylaxis. The Suncus murinus is useful as a new experimental animal model for motion sickness.

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Endocrine correlates of susceptibility to motion sickness.

Kohl RL.

Motion sickness releases ACTH, epinephrine, and norepinephrine. We are interested in endocrine responses to motion sickness, in adaptive responses leading to the resolution of the syndrome, and in how antimotion-sickness drugs influence the endocrine responses. Susceptible or insusceptible subjects were administered antimotion-sickness drugs prior to stressful stimulation. Insusceptible subjects displayed more pronounced elevations of ACTH, epinephrine, and norepinephrine after stressful motion. Predrug levels of ACTH were higher in insusceptible subjects (p less than 0.01). Acute blockade of hormone responses to stressful motion or alteration of levels of ACTH by drugs was not correlated with individual susceptibility. No correlation was apparent between epinephrine and ACTH release. These endocrine differences may represent neurochemical markers for susceptibility to motion, stress, or general adaptability, and it may be that the chronic modulation of their levels might be more effective in preventing motion sickness than the acute blockade or stimulation of specific receptors.

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