We have reported that closure of eyes has an activity effect upon caloric nystagmus and an inhibitory effect upon the nystagmus during the rotation. The purpose of the present study is to elucidate the influence upon nystagmus of the three different states of eye-opening in a bright room, eye-opening in a dark room and eye-closure, with the help of E.E.G. findings in the Parieto-Occipital lead.
Following three experiments were conducted on an assumption that one is optically stimulated and visually alert in the state of eye-opening in a bright room, visually alert but not optically stimulated in the state of eye-opening in a dark room and neither optically stimulated nor visually alert in the state of eye-closure.
Experiment I.; In the above-mentiond three different states, Wtist's pendular test was performed with 10 normal persons using the damped pendular rotation chair worked by a spring, and the eye speed of nystagmus in both rapid and slow phases was recorded during the rotation.
Experiment 2. ; Kobrak's deceleration test was performed with 10 normal persons using the same chair as used in Experiment I in the three different states. Eye speeds of nystagumus during the rota- tion and of postrotatory nystagmus were recorded.
Experiment 3.; Eye speed of caloric nystagmus evoked with 30°C, 20cc water in 6 normal persons was recorded in the three different states.
Result
1) Eye speed of nystagmus during the rotation invariably decreased in the following order; in the state of eye-opening in a bright room, eye-opening in a dark room and eye-closure.
2) Eye speeds of postrotatory nystagmus and of caloric nystagmus were invariably larger in the state of eye-opening in a dark room than in the state of eye-opening in a bright room, and they were usually smaller in the state of eye-closure than in the state of eye-opening in a dark room.
3) As the result of analytical study of the three different states, an assumption was made that both optic stimulation and visual alertness existed in the state of eye-opening in a bright room, the former being deprived in the state of eye-opening in a dark room and that neither of them operated in the state of eye-closure.
4) Based on the assumption mentioned in the result (3), an inference was drawn that deprivation of optic stimulation exerted an activating effect upon postrotatory nystagmus and caloric nystagmus and an inhibitory effect upon the nystagmus during the rotation. Deprivation of visual alertness on the other hand had an inhibitory effect upon all three kinds of nystagmus examined.
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