[The low-frequency EEG component in the healthy subject and its changes as affected by acutely developing foci at the level of the diencephalon and brain stem structures].

The data are given of the analysis of the low-frequency EEG component (LF EEG--0.2--2.0 Hz) of 34 healthy subjects and 36 patients examined in dynamics in the acute period after operations: ablation of a tumour localized at the level of the diencephalon and the level of the brainstem. The LF EEGs were analyzed by a special program: auto- and crosscorrelation functions and power spectra were estimated. In the norm LF EEGs were characterized by mosaics, various frequencies and periodicity in various cortical areas, they appeared with interhemispheric asymmetry, depended on the EEG type--dominance or lack of the alpha-rhythm. In patients in the post-operative period the LF EEGs were changed; in favourable terminations, at first the period of oscillations and the coefficient of correlation increased, then they tended to normalization. In unfavourable terminations, with gross pathological foci in these areas, the LF EEGs acquired a synchronized character, with a higher frequency than in the norm.