AUDITORY RESPONSE FROM THE CEREBELLUM BY MEANS OF ULTRAMICRO-ELECTRODE

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Shinoda studied on the evoked potentials and the unitary activities by means of the superfine micro-electrode (each tip diameter measures 0.1 u)from cerebellum in cat by the sound and electrical stimulations. 1)The evoked potentials by the sound stimuli could be recorded from lobus simplex, . tuber vermis and declive, and they disappeared by bilateral destruction of the inferior colliculus, but not affected by bilateral destruction of the medial geniculate body and ce- rebral auditory cortex.The auditory pathways, therefore, seem to be projected to the cerebellar cortex through the inferior colliculus. 2)The evoked potentials by the electrical stimulation of the cerebral auditory cor- tex were recorded from tuber vermis, lobus simplex and declive.From the results of the experiment, the projection pathway to the cerebellar cortex through the cerebrum, was suggested. 3)The latency of the evoked potentials which were recorded from tuber vermis by the electrical stimulation on the peripheral acoustic nerve was 2∼4 msec.Since the la- tency of the responses by the sound stimulation was 10∼11 msec, the results can be well explained by considering a possibility of stimulation to the vestibular or facial nerve fibers. 4)Only one thirtieth to fiftieth of the unitary spikes which were recorded from tu- ber vermis could be certified to have a certain relation with sound stimuli. 5)From the results described in 3)and 4), it might be thought that several func- tional areas are overlapped each other in the cereberal cortex. 6)The elements responded to sound stimulation had two types ; one was the inhi- bited type and the other was the facilitated type by the sound stimuli, and both of them showed the slow adaptation to the sound stimulation. 7)The unitary spikes by the sound stimulation which were recorded from cere- bellum showed high threshold of more than 80 db.The high responsive threshold in the cerebellar cortex showed resemblance to the threshold of audito-muscular reflexes. On thecontrary, the responsive threshold in the cerebral cortex was quite alike to the actual auditory threshold.