Kohji Tokumasu

Eye Movements from Single Utricular Nerve Stimulation In The Cat

Single utricular nerves were electrically stimulated in the cat. The induced eye movements were almost pure rotation in both eyes. In addition to rotation, there were upward shifts in the ipsilateral eye and downward shifts in the contralateral eye. Slight contralateral horizontal shifts occurred in both eyes. Tension increases in extraocular muscles were strongest in the ipsilateral superior oblique and contralateral inferior oblique. They were weaker in the ipsilateral superior rectus and contralateral inferior rectus, and were weakest in the ipsilateral medial rectus and contralateral lateral rectus muscles. The tension increase in the contralateral inferior oblique and the lateral rectus was studied by changing the frequency of stimulation. The utricular-ocular reflex reacted from very low to very high frequencies, as high as 1600 cps. In comparison, the cupulo-ocular reflex arc did not respond well to high frequencies. The temporal summation in the vestibulo-ocular reflexes appeared different between...

LXXII Implantation of Electrodes near Individual Vestibular Nerve Branches in Mammals

In the vestibular labyrinth of mammals there are five separate end-organs, the cristae of the three semicircular canals and the maculae of the utricle and saccule. These end-organs normally react to mechanical stimulation, the cristae to rotatory acceleration, and the maculae to linear acceleration and to gravity. By using natural stimuli, however, it is difficult to selectively stimulate single receptors.

A Study of the Current Spread on Electric Stimulation of the Individual Utricular and Ampullary Nerves

In the cat, single vestibular nerve branches were electrically stimulated through implanted electrodes. Different combinations of extraocular muscles were activated by each of the single vestibular nerve branches, and there were three frequency-dependent contraction modes, i.e. the lateral-canal, the verticalcanal and the utricular type. It was shown that these could be utilized for detecting whether single or combined vestibular nerve branches were stimulated.

Study on vomiting related to the vestibulo-autonomic reflex.

The purpose of this study was to investigate the neural pathway from the vestibular labyrinth to the medullary vomiting center in the cat, using electrophysiological techniques. During electrical stimulation of the canal nerve, we found conflicting results: the pressure in the stomach sometimes increased, and sometimes decreased. There might be several neural structures between the semicircular canal nerve and the vomiting center in the dorsolateral portion of the reticular formation of medulla oblongata. Retching or vomiting-like behavior during both respiration and movement of the stomach was recorded during stimulation at several sites in the lateral medullary reticular formation. However, the evoked unit activities were not always induced by stimulation of the canal nerve.

Study on Ranges of Fluctuated Hearing Disturbances in Meniere's Disease

The threshold of hearing were investigated by repeated audiometries in the cases of Menieres disease, who were treated mostly medicinally. The test subjects were 38 patients including 8 bilateral cases. Mean period for follow-up-study was over one year. Audiograms obtained in both the first and the final test and in both the most improved and the most worsened stage were compared. The results, which were confirmed statistically are as follows:In unilateral cases, the mean value of the threshold of hearing in 8000Hz was higher than in 500Hz and the gain of improved hearing in 500Hz was 16.7dB in the best hearing stage. The difference of thresholds in 500Hz between in the best and the worst stage was 27.5dB in unilateral cases.The threshold in 8000Hz in the worst stage was higher in bilateral cases than in unilateral.

Lack of relationship between the existence of down beat nystagmus and the height of the axial process in Basilar impression

Basilar impression can be diagnosed according to the measurement of the height of the axial process seen on the X-ray. Down beat nystagmus is considered to be a characteristic finding in basilar impression, however, such is not apparent in all cases. In our 4 cases, the relationship between the existence of down beat nystagmus and the height of the axial process had no apparent relationship.