[Spectral analysis of the human EEG in acutely developing foci of irritation at the diencephalic and brain stem levels]. / Spektral'nyi analiz EEG cheloveka pri ostro razvivaiushchikhsia ochagakh razdrazheniia na urovne dientsefal'nykh i stvolovykh otdelov mozga.

The dynamic study of EEG spectra and coherence in 52 patients in early period after tumor ablation at the diencephalic (27 patients) and brainstem (25 patients) levels with favourable (24 patients) and lethal (28 patients) outcomes revealed a dependence of their changes on the reversibility or irreversibility of pathological irritation of these brain levels. At regressively developing foci and retained compensatory mechanisms characteristic changes of EEG relations were seen in the central cortical areas, i. e. in cortical projection zone of the nonspecific thalamic pathways. The changes observed consisted of EEG synchronization in the band of 7 cps and sharp coherence increase while changes of EEG correlations in other cortical areas were unsimilar. Gradual EEG normalization with alpha-rhythm restoration passed through the stage of sigma-rhythm and slow sleeplike waves which indicated the safety of brainstem-subcortical hypnogenic systems. In patients with destructive foci at the diencephalic and brainstem levels, i. e. under conditions of brain functioning similar to "cerveau isolé" and "encephale isolé",--a general coherence decrease and EEG synchronization in the band of 5 cps, or generalized slow, monomorphic oscillations were observed.

[Spectral analysis of the EEG and intracortical connections in the presence of a pathologic focus at different levels of the human brain]. / Spektral'nyi analiz EEG i intrakortikal'nye sviazi pri nalichii patologicheskogo ochaga na raznykh urovniakh golovnogo mozga cheloveka.

EEG spectral analysis in 68 patients with focal brain lesions has shown that EEG power spectra are characterized by greatest changes in the focal zone, as manifested in the augmenting of the slow component and diminution of the alpha-component. By means of phasic analysis it has been established that the slow component is generated in the focal zone. Analysis of the complex function of EEG coherence detected different variants of changes in the spatial-temporal organization of cortical electrical activity, determined by localization of the focus and the extent of its impact on the brain. The revealed discordance of EEG connections, diminution of coherence in some parts of the hemispheres with simultaneous enhancement in the others, manifested differently in different physiological rhythms ranges, reflects an impairment in the structure of intracortical connections of electrical processes, which is typical of the normal brain.

[Analysis of human EEG spectra in a state of relative and "operative rest" according to A. A. Ukhtomskii]. / Analiz spektrov EEG cheloveka v sostoianii otnositel'nogo i "operativnogo pokoia" poi A. A. Ukhtomskomu.

The analysis of EEG in 40 healthy subjects showed that power spectra, coherence and phase spectra strongly vary in different subjects and that their spatial distribution among cortical areas bears individual properties. General characteristics of the spectra and mean levels of EEG coherence are stable, but details of power spectra, coherence and phases in healthy subjects are very unstable even within short time intervals. In the process of developing in the subject of a stable, ordered by experimenter state of a strained expectation of the signal to immediate activity--of "operative rest", according to A. A. Ukhtomsky--a uniform for all subjects structure of connections is shaped in frontal-central cerebral parts, which is manifested in a specific pattern of coherence spectrum.

[Symmetry and stability of the EEG spectra of healthy subjects]. / Simmetrichnost' i stabilnost' spektrov EEG zdorovogo cheloveka

Stability and symmetry of power spectra and the EEG coherence function have been investigated in 40 healthy subjects with different characteristics of cerebral electrical activity. It has been shown that the power spectra in all healthy subjects are characterized by a high degree of symmetry and stability. The average levels of coherence of the symmetric points of the right and left hemisphere proved to be a reliable EEG characteristics of a healthy subject. In contradistinction, the pattern of the coherence spectrum displays considerable variability and non-stability. Subjects with a desynchronized EEG differ from those with alpha-rhythm predominance by the highest coherence and similarity of the spectra along with their low stability in the anterior parts of the hemisphere which testifies to a high dynamic integration of the frontal systems.