Vestibulo-Autonomic Reflex and Vestibulo-Ocular Reflex in Space Adaptation Syndrome

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We tried to investigate the mechanism of space adaptation syndrome to reveal a relationship between changes of the vestibulo-autonomic reflex and those of the vestibulo-ocular reflex from 1995 to 1996. Our study did not obtained so many data since we had much time to care and train a rhesus monkey. The equipment we used at our university to invoke spatial disorientation in animal satisfactorily simulates the occurrence of space adaptation syndrome. Futher experiment that we continue will reveal some important results as follows : 1.We confirm that Bolivian rhesus monkeys are suitable animals in simulation experiments, since they exhibit symptoms very similar to those experienced by astronaut during space motion sickness. 2.Double rotation stimulation (yaw and pitch ax es) is effective in simulating space adaptation syndrome on earth. 3.In the present study, since there would be no obvious effects of phase lag and velocity differences between yaw and pitch rotation on symptoms of space … More adaptation syndrome, we should apply a simpse stimulation strategy in which velocity of yaw rotation is equivalent to that of pitch rotation without phase lag. 4.An increase of heart rate and a decrease in blood pressure will be observed when the rhesus monkeys were exposed to double rotation stimuli, which seems to result from the vestibulo-autonomic reflex.We will infer that the inputs producing these responses come from the otolith receptors. These results should indicate a modification of vestibulo-sympathetic reflexes. 5.Power spectral analysis of the heart R-R interval would be also consistent with sympathetic excitation, further supporting the parallel with space adaptation syndrome. 6.A significant change would not be observed in measurements of facial blood flow using a laser Doppler technique, although a slight decrease would be observed. 7.Double rotation stimulation will cause spontaneous horizontal eye movements, so-called nystagmus, although vertical nystagmus would not observe. 8.We shall analyze the time constant and gain of slow phase eye velocity to ex amine the nature of horizontal nystagmus during double ax es rotation. It would be possible that a modification of the neural integrator and velocity storage resulted from the double rotation stimulation. Our study shall provide contributions toward revealing the mechanisms of space adaptation syndrome. Less