SOUND STIMULATION AND AUTONOMIC CENTRES

Abstract

Habituation of the orientation reflex (O.R.) to repetitive sound stimulation (pure tone and bell) was observed in EEG, to study the influences whi- ch the changes of the nature of sound and the acti- vity level of autonomic centres have on habituation speed.
In the chronically implanted rabbits, bipolar electrodes were placed in the cortical and subcor- tical (including autonomic centres) regions, from which EEG were recorded unanesthetized.
EEG patterns of O.R. can be divided into two, namely desynchronized type and synchronized ty- pe. The activity of background EEG was divided to high, moderate and low level. Generally, in the high O.R. was not clear and habituated earliest when it appeared, on the other hand, in the low it was recognized most sharply and habituated latest.
The process of the habituation, in which the O.R. duration shortened and the component frequ- encies changed, was irregular and waving.
Generally, habituation was delayed by increas- ing tone intensity, and in the low and moderate background EEG, it arose simultaneously in the cortical and subcortical regions.
At 70 phon of 8000c/sec., O.R. was generally susceptive to habituation, and during 300 to 2000c/ sec., which had no frequency specificity of sound for habituation speed, clearest individual difference was recognized. In 4000c/sec., the habituation speed was in between 2000 and 8000c/sec. and ma- nge.
Still more, the tendency was recognized that electrical stimulation of the b-stmpathetic zone of the hypothalamus and the medial preoptic area facilitated habituation, while stimulation of the c-pa- rasympathetic zone and the lateral preoptic area delayed it. And these possible reasons were dis- cussed.