Cyclical processes in neuronal populations of the cat somatosensory cortex during extero- and interoceptive activation and in the course of its extinction.

The EEG reactions were recorded in chronic experiments in awake cats and the slow periodic changes in the frequency of the multicellular impulse activity were observed at points (standard localization) of the somatosensory (1) zone of the cortex. Results of the analysis of both processes were combined in graphs in a single time scale. The correlation of the expressivity of the activation reaction and degree of modulation of the cyclical fluctuations of the frequency of the impulse activity were followed both during the action of exteroceptive (conditional, light; unconditional, sound) and the interoceptive (mechanical and chemical) stimuli. A particular characteristic of the interoceptive stimulation as compared with the exteroceptive consisted in the inertia of the respondent reaction and the lesser contrast in relation to the background. During the extinction of the responses the decrease in the activation reaction correlated with a decrease in the initial (after the switching on of the stimulus) fluctuation of the frequency of the multicellular impulse activity. The data obtained serves as proof of the unity of the two processes: the regulation of the activation of the brain and the regulation of the periodicity of the neuronal impulse activity.