[Extinction of brain activation responses to direct electrical stimulation of its structures in normal awake cats]

In unrestrained cats, repeated electric stimulation of the mesencephalic reticular formation (MRF), center median (CM) of the thalamus, and different cortical areas: both the low--and the high--threshold points (in regard to the brain activation), with the threshold strength current evoked similar EEG reactions of activation which diminished and disappeared after 3--5 repetitions of the stimuli. The moderate strength current evoked, apart from the EEG activation, pseudoviolent movements (turning of the head, etc.) and changes in the breathing rate. All these reactions could be extinguidhed by sufficient number of repetitions of stimuli, the effector reactions disappearing first, the EEG changes--last. The essential difference of the stimulation effects emerged when the strong current stimulation was used. In this case, when stimulating the high-threshold cortical points, the EEG and effector reactions could be abolished during long enough repetition of the stimuli, but it was impossible when stimulating the low-threshold cortical points, the MRF or CM: all the reactions stayed intense and stable, the animals became highly irritated. The data obtained are discussed from the point of view of the authors' concept of the interaction between the activating and integrative analysing mechanisms of the brain.