猫下丘ニューロンの音刺激に対する応答様式に関する実験的研究

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概要

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• The purpose of the present paper is to study the signal transmission in the inferior colliculus and to show the difference between responses of the inferior colliculus and of the cochlear nucleus.Young adult cats were anesthetized with Nembutal and controlled with the respirator. After opening the skull, the inferior colliculus was exposed to insert u tangsten electrode. Then the two-tone stimuli were given by a condenser speaker introduced to the external meatus. The response areas, PST histograms, interval histograms and spike rates were obtained.Response areas were classified into 7 types. Some response areas in the inferior colliculus were narrower than in the cochlear nucleus and some ones were broader. It suggests that neural mechanisms are more complex in the inferior colliculus than in the cochlear nucleus.The changes of spike distribution patterns (PST histograms) of the inferior colliculus to a test tone caused by a preceding conditioning tone were classified into 4 types. In the first type, the change of the patterns was more distinct as the interval of two tones became shorter. In the second, the change was most distinct when the interval was about 5omsec. In the third, the change was complicated related to the time interval. In the fourth, no change was observed.Also, chages of spike rate were classified into 4 types. In the first, the decrease of the spike discharges was more distinct as the interval became shorter. In the second, the decrease was most distinct when the interval was about lomsec. In the third, the decrease was observed as long as the interval was 200msec. In the fourth, no reduction was observed.From these results, it may be suggested that there are neurons which have simple connections and neurons which receive many neural inputs in the inferior colliculus of the cat. Efferent inhibition may be concernd in the complex neurons. Exponential change of the spike rate may be explained by lateral inhibition. In the cochlear nucleus, exponential changes of the spike rate were frequently observed, while in the inferior colliculus, the changes were rarely obtained.From the results the author infered that analysis of simple signals, i.e. pitch and intensity of tones is accomplished in the lower station than the inferior colliculus and that analysis and integration of higher degree is accomplished in the inferior colliculus.

著者

• 岩田 洋

  名古屋大学医学部付属病院分院耳鼻咽喉科

• 岩田 洋

  名古屋大学大学院医学研究科外科系耳鼻咽喉科学

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