Tsunemasa Sato

The inferior collicular potential in acoustic and electrical stimulation of the cochlea: an experimental study of guinea pig.

We made experiments of the inferior collicular potentials in acoustic and electrical stimulation for the purpose of studying fundamental issues for cochlear implantation. Guinea pigs with normal Preyers reflex were used for this study. The results were as follows: (1) in acoustic stimulation relatively wide and large waveforms were gained but in electrical stimulation sharp and narrow ones were gained, (2) in acoustic stimulation the input-output curve of latency and amplitude was biphasic but in electrical stimulation it was monophasic. For this reason, in acoustic stimulation by click, when the intensity is low (under 80 dB SPL) stimulus site would be comparatively low frequency fibers. When the intensity is high (over 80 dB SPL) the stimulus site would shift to high frequency fibers. Therefore, many more neighboring fibers start responding. This results in biphasic input-output curves of latecy and amplitude. By electrical stimulation, however, it would be possible to stimulate only a restricted area among the bipolar electrode. Therefore, as the intensity increases, the response amplitude increases and becomes saturated at a constant level. This results in monophasic input-output curves of latency and amplitude.

Primary Position Upbeat Nystagmus; A Report of Three Cases.

Primary position upbeat nystagmus (PPUN) is an extremely rare disease, and there is no general agreement about its etiology. Most investigators believe, however, that it is associated with disorders in areas extending from the brain stem to the cerebellum. We studied the etiology of and lesions responsible for this disease from the results of various tests and examinations conducted in 3 patients who had different clinical courses. Finding 1: Horizontal and vertical eye movements showed dissociation in Case 2, suggesting that different nerve tracts are involved in these movements. Finding 2: All 3 patients showed evidence of disorders in the brain stem and cerebellum, suggesting that the conduction route between the brain stem and the cerebellum was impaired.

耳鳴の局在に関する研究 方向感自動記録装置による測定:―方向感自動記録装置による測定―

The lateralization of tinnitus on the cranium was measured by a directional hearing device, which can generate binaural time or intensity differences for various sound sources. Tracings of sound locomotion are recorded as sawteeth-like waves by repetition of the dial operation in the right and left directions.First, the central and lateral sound images on the cranium were measured by method of adjustment for subjects with normal hearing. The range of the values was determined after three measurements per day for three days. The regions of these locations of sound impression were in close agreement, and 67% of 20 normal control subjects showed stable results.Next, 30 subjects with normal hearing ability and monaural tinnitus were tested. The location of tinnitus on the cranium was determined after localization of the sound impression in the central and lateral positions by the method described above. The results were as follows: in 53% of the subjects the results were stable; 46% showed agreement between the positions of tinnitus and the lateral side, and 27% showed a more medial impression of tinnitus than the lateral position.This method has no restrictions as a clinical test. The fact that the position of tinnitus may disagree with the lateral impression on the cranium was clarified by these experiments.

A Long-term Follow-up Stady on Perceptive Deafness (3-8 years)

Hearing of patients of perceptive deafness, most of them due to unknown cause, was studied for more than 3 years until 8 years. The hearing loss was not changed in 35 cases but it was aggravated in 20 cases and fluctuated in 13 cases in this series.The hearing impairment of aggravated group was initiated at the high frequencies and extended to the low frequencies.The hearing loss at low frequeucies was larger in fluctuated group than in aggravated group.One patient in aggravated group showed that the aggravation of haring impairment in one ear was followed by that in the other ear. One patient in fluctuated group showed the fluctuotion of hearing in both ear simultaneously.