Altered coriolis stress susceptibility in essential hypertension.

Lockette W, Shepard N, Lyos A, Boismier T, Mers A.

Department of Medicine, Wayne State University Medical School, Detroit, MI 48201.

Patients with hypertension frequently have vague complaints of dizziness and many other symptoms experienced by healthy individuals with motion sickness. We examined vestibular function in patients with essential hypertension, and we determined whether patients with essential hypertension are more prone to motion sickness using Coriolis stress testing. Vestibular function and Coriolis stress susceptibility were measured in 12 normotensive (NT) and seven asymptomatic patients with mild essential hypertension (HT). The Coriolis stress susceptibility index (CSSI) was calculated from the number of head movements in the four cardinal directions an individual could complete while being rotated in a computerized chair at increasing velocity before they developed motion sickness. The patients with hypertension had normal vestibular function and normal vestibuloocular responses as measured by standard techniques. Subjects with hypertension had significantly decreased Coriolis stress susceptibility scores compared to normotensive subjects (NT, 29.70 +/- 4.8; v HT, 5.48 +/- 2.0, P less than .001) and significantly decreased suppression of postrotatory nystagmus (NT, 44.5% +/- 3.8; v HT, 19.1% +/- 6.9, P less than .05). Medical treatment of hypertension did not result in an increased tolerance to provocative stimuli for motion sickness. It is suggested from our data that an increased susceptibility to motion sickness and abnormal vestibular responses to normal motion may account for many of the vague symptoms of "dizziness" reported by a large number of hypertensive patients.

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A motion sickness maximum around the 0.2 Hz frequency range of horizontal translational oscillation.

Golding JF, Mueller AG, Gresty MA.

Department of Psychology, University of Westminster, London, United Kingdom. goldinj westminster.ac.uk

BACKGROUND: Low frequency translational oscillation can provoke motion sickness in land vehicles, ships and aircraft. Although controlled motion experiments indicate a progressive increase in nauseogenicity as frequency decreases toward 0.2 Hz, few data are available on the existence of a definite maximum nauseogenic potential of motion around 0.2 Hz, or decreased nauseogenicity below this frequency. HYPOTHESIS: Nauseogenicity should be maximal around 0.2 Hz. METHODS: We selected 12 subjects for high motion sickness susceptibility, and they were exposed to horizontal sinusoidal motion (1.0 m.s(-2) peak acceleration) at 3 different frequencies (0.1, 0.2 and 0.4 Hz), at 1-wk intervals at the same time of day, according to a factorial design. Subjects were seated comfortably in the upright position with head erect. Fore-aft motion was through the body and head X-axis. Motion was stopped (motion endpoint) at moderate nausea or after 30 min. RESULTS: The proportion of subjects experiencing moderate nausea was maximal at the intermediate frequency: 8/12 at 0.1 Hz, 12/12 at 0.2 Hz, 7/12 at 0.4 Hz. The mean time to motion endpoint was significantly (p < 0.01) shorter at the intermediate frequency: 18.0 min at 0.1 Hz; 11.2 min at 0.2 Hz; 20.2 min at 0.4 Hz. Similar frequency patterns emerged for other sickness ratings. The equivalent times to achieve moderate nausea using estimated values to correct for subjects who reached the 30 min time cut-off were: 22.7 min at 0.1 Hz; 11.2 min at 0.2 Hz; 28.1 min at 0.4 Hz. CONCLUSIONS: A maximum nauseogenic potential around 0.2 Hz was substantiated.

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Locomotion and motion sickness during horizontally and vertically reversed vision.

Takahashi M, Saito A, Okada Y, Takei Y, Tomizawa I, Uyama K, Kanzaki J.

Department of Otolaryngology, Keio University School of Medicine, Tokyo, Japan.

Locomotion and motion sickness during reversed vision were studied in ten normal subjects and a patient with bilateral labyrinthine loss. Whereas horizontal reversal produced moderate to severe gait disturbances as well as motion sickness in all normal subjects, vertical reversal failed to induce such symptoms. The patient, being free of motion sickness during both reversals, could not walk straight during horizontal reversal. The difference in the strength of sensory mismatch between both directions seemed to result from a difference in the role of vision for spatial orientation which is produced by the proprioceptive as well as otolithic inputs of gravity.

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Prediction of space motion sickness susceptibility by disconjugate eye torsion in parabolic flight.

Diamond SG, Markham CH.

Department of Neurology, UCLA School of Medicine 90024-1769.

The hypothesis of asymmetric otolith function asserts that physiological or anatomical differences in the two sides of the bilateral gravity-sensing otolith apparatus of the inner ear may be well compensated on Earth, but when exposed to novel gravitational states, the prior compensatory stratagems may be ineffective, leading to unstable vestibular responses and causing the phenomenon of space motion sickness. To investigate this hypothesis, spontaneous eye torsion, a reflex governed by the otolith organs, was examined in the upright position during the hypo- and hypergravity of parabolic flight aboard NASA's KC-135 aircraft in nine former astronauts whose history of space motion sickness was revealed after data analysis had been completed. Results showed that astronauts who had been sick in space had significantly higher scores of disconjugate eye torsion in parabolic flight, and that their responses were consistently different in 1.8 G relative to 0 G compared to astronauts who had not been sick in space. In 1 G, there were no differences in disconjugate eye torsion between the subjects. The results support the asymmetry hypothesis and offer a possible predictive test of space motion sickness.

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Decreased susceptibility to motion sickness during exposure to visual inversion in microgravity.

Lackner JR, DiZio P.

Ashton Graybiel Spatial Orientation Laboratory, Brandeis University, Waltham, MA 02254-9110.

Head and body movements made in microgravity tend to bring on symptoms of motion sickness. Such head movements, relative to comparable ones made on Earth, are accompanied by unusual combinations of semicircular canal and otolith activity owing to the unloading of the otoliths in OG. Head movements also bring on symptoms of motion sickness during exposure to visual inversion (or reversal) on Earth because the vestibulo-ocular reflex is rendered anti-compensatory. Here, we present evidence that susceptibility to motion sickness during exposure to visual inversion is decreased in a 0G relative to a 1G force background. This difference in susceptibility appears related to the alteration in otolith function in 0G. Some implications of this finding for the etiology of space motion sickness are described.

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Motion sickness susceptibility in parabolic flight and velocity storage activity.

DiZio P, Lackner JR.

Ashton Graybiel Spatial Orientation Laboratory, Brandeis University, Waltham, MA 02254-9110.

In parabolic flight experiments, we have found post-rotary nystagmus to be differentially suppressed in free fall (OG) and in a high gravitoinertial force (1.8G) background relative to 1G. In addition, the influence of postrotary head movements on nystagmus suppression was found to be contingent on G level. The nature of this pattern indicated a G-dependency of the velocity storage and dumping mechanisms. Here, we have rank-correlated susceptibility to motion sickness during head movements in OG and 1.8G with the following: a) the decay time constant of the slow phase velocity of post-rotary nystagmus under 1G, no head movement, baseline conditions, b) the extent of time constant reduction elicited in OG and 1.8G; c) the extent of time constant reduction elicited by head tilts in 1G; and d) changes in the extent of time constant reduction in OG and 1.8G over repeated tests. Susceptibility was significantly correlated with the extent to which a head movement reduced the time constant in 1G, was weakly correlated with the baseline time constant, but was not correlated with the extent of reduction in OG or 1.8G. This pattern suggests a link between mechanisms evoking symptoms of space motion sickness and the mechanisms of velocity storage and dumping. Experimental means of evaluating this link are described.

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Motion sickness severity and physiological correlates during repeated exposures to a rotating optokinetic drum.

Hu S, Grant WF, Stern RM, Koch KL.

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

Fifty-two subjects were exposed to a rotating optokinetic drum. Ten of these subjects who became motion sick during the first session completed two additional sessions. Subjects' symptoms of motion sickness, perception of self-motion, electrogastrograms (EGGs), heart rate, mean successive differences of R-R intervals (RRI), and skin conductance were recorded for each session. The results from the first session indicated that the development of motion sickness was accompanied by increased EGG 4-9 cpm activity (gastric tachyarrhythmia), decreased mean successive differences of RRI, increased skin conductance levels, and increased self-motion perception. The results from the subjects who had three repeated sessions showed that 4-9 cpm EGG activity, skin conductance levels, perception of self-motion, and symptoms of motion sickness all increased significantly during the drum rotation period of the first session, but increased significantly less during the following sessions. Mean successive differences of RRI decreased significantly during the drum rotation period for the first session, but decreased significantly less during the following sessions. In conclusion, we have demonstrated that the development of motion sickness is accompanied by an increase in gastric tachyarrhythmia, and an increase in sympathetic activity and a decrease in parasympathetic activity, and that adaptation to motion sickness is accompanied by the recovery of autonomic nervous system balance.

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[The motion sickness under reversing goggles (1st report)]

[Article in Japanese]

Saito A, Takahashi M, Okada Y, Takeuchi I, Takei Y, Uyama K, Tomizawa I, Kanzaki J.

Department of Otolaryngology, Keio University School of Medicine, Tokyo.

We observed locomotion and motion sickness in 10 normal adults wearing reversing goggles while moving outdoors. Horizontal reversal of the visual field produced moderate to severe ataxia and motion sickness in all subjects except one. There was marked variability in the sensitivity among different subjects. In contrast, vertical reversal produced no symptoms. Confusion of information relation to spatial orientation possibly caused both the motion sickness and abnormal locomotion. Horizontal reversal of visual information produces disorientation because visual information is equal in importance to that from the semicircular canals. In the case of vertical reversal of visual information, orientation may be assured by gravity. The present study suggests that motion sickness is a biological signal alerting the organism to loss of spatial orientation rather than a mere autonomic symptom produced by mismatched sensory information. It appears that motion sickness is accompanied by dysequilibrium and abnormality of locomotion.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2037947&dopt=Abstract motion sickness