[Intracerebral EEG functioning as a reflexion of the systemic brain organization in norm and pathology]. / Mezhtsentral'nye otnosheniia EEG kak otrazhenie sistemnoi organizatsii mozga cheloveka v norme i patologii.

The authors summarized the EEG findings and defined the nature of intercentral EEG relationships in different functional states of healthy subjects and patients with organic cerebral pathology based on coherence analysis. The EEG features typical of healthy subjects were identified: an anterior-posterior gradient of the mean coherence and the character of cortical-subcortical relationships in the anterior cerebral structures. Right- and lefthanded subjects showed the frequency and regional differences in EEG coherence, which reflected, mainly, specific intracortical relationships. Development and regression of pathologic signs in right- and lefthanded patients with organic brain lesions are thought to be determined by these differences. As distinct from cortical pathology, lesions of regulatory structures (diencephalic, brainstem, and limbic) were shown to produce more diffuse changes in intercentral relationships with a tendency to reciprocity. Intercentral relations, including their interhemispheric differences, varied with changes in the functional state of healthy subjects (increase and decrease in the level of functioning). A certain time course of changes in intercentral relationships was also revealed in patients with organic brain lesions during recovery of their consciousness and mental activity. Changes in the dominance of activity of individual regulatory structures are considered to be one of the most important factors that determine the dynamic character of EEG coherence.

[The hemispheric relationships of the human brain during the recovery of consciousness after a long-term coma: an EEG analysis]. / Polusharnye otnosheniia bol'shogo mozga cheloveka v protsesse vosstanovleniia soznaniia posle dlitel'noi komy: EEG-analiz.

Analysis of the intra- and interhemispheric EEG coherence in the dynamics of coma regress and its comparison with the clinical stages of postcomatose recovery period revealed both specific interhemispheric rearrangements of the structure of intercentral functional relations, which developed in parallel with the recovery at first of the visual, and then speech functions, and the adaptive-compensatory changes in activity of the regulatory systems, which provide the recovery of mental functions. It is emphasized that the interhemispheric EEG coherence asymmetry, its character and dynamics are significant for formation of neurophysiological mechanisms of consciousness and the course of compensatory processes under the extreme conditions.

[A dynamic comparison of the interhemispheric asymmetry in the coherence of the human EEG in tumorous lesions of the diencephalic and hemispheric brain structures under different conditions of cerebral compensation]. / Sopostavlenie dinamiki mezhpolusharnoi asimmetrii kogerentnosti EEG cheloveka pri opukholevom porazhenii diéntsefal'nykh i polusharnykh struktur mozga v raznykh usloviiakh tserebral'noi kompensatsii.

In patients with diencephalic (30 persons) and hemispheric tumors (17 persons with the left-side and 18 ones with the right-side localization) EEG coherence was studied before and in early terms (12 days) after surgery in comparison with the right-handed healthy subjects. It was shown that integral coherence asymmetry coefficient before surgery were informative for a prognosis of the postsurgery treatment. Changes of absolute coherence levels in the central-frontal cortical areas were also informative. In patients with the light postsurgery course of treatment coherence levels were higher than those in the healthy subjects and increased after surgery. They decreased in patients with aggravated character of postsurgery period. Recovery terms were shorter in patients with the left hemispheric tumor localization than those with the right hemispheric one. The similarity of EEG coherence changes was observed in patients with the diencephalic and right hemispheric tumor localization. These results suppose the functional connections between these structures which are significant for compensatory processes in early terms of postsurgery period after brain tumor ablation.

[The specificity of the recovery processes in the brain of patients with diencephalic and hemispheric lesions (an EEG coherence analysis)]. / Spetsifika vosstanovitel'nykh protsessov mozga u bol'nykh s diéntsefal'nym i polusharnym porazheniem (kogerentnyi analiz EEG).

Inter- and intrahemispheric EEG coherence and its asymmetry was studied in 65 patients with head tumors, 70 patients with head injury before and after surgery. Control characteristics were obtained from 20 healthy subjects. EEG and clinical data were compared in patients with right and left hemispheric tumors. Patients with left hemispheric tumors were characterized by a shorter recovery period (EEG and clinical data), earlier stage of diencephalic activation, and by the right hemispheric asymmetry of EEG coherence. These characteristics were not observed in patients with right hemispheric tumors. Interhemispheric coherence decreased to a higher degree in patients with right hemispheric damages in comparison to those with the left ones, especially in the central leads in the theta-range. In patients with the left foci the maximal interhemispheric coherence decrease was observed in the frontal recordings. Coherence characteristics and their dynamics were shown to be alike in patients with right hemispheric and diencephalic damages.

[The reflection of the adaptive restructurings of the human brain in disordered cerebral functions in the parameters of interhemispheric asymmetry in EEG coherence]. / Otrazhenie adaptivnykh perestroek mozga cheloveka pri narushenii tserebral'nykh funktsii v parametakh mezhpolusharnoi asimmetrii kogerentnosti EEG.

In this work was studied a hemispheric specificity of the human brain in a realization of adaptive-compensatory reactions of the CNS. The interhemispheric correlation of EEG coherence functions of the left and the right hemispheres was computed in patients with brain focal lesions in early postsurgery period after an extraction of the medially-located tumor or in far-off time after a hard brain injury (i.e. at different stages of cerebral compensation). The observed peculiarities of changes of the interhemispheric biopotential relations revealed the dynamic character of preferable switching on the right or the left hemisphere in a formation of adaptive-compensatory brain reactions. The specificity of this switching depended on the stage of the pathologic process and reflected the degree of consciousness disturbance.

[The reflection of compensation processes in the structure of the EEG spatial-temporal relationships in patients with disordered brain regulatory mechanisms]. / Otrazhenie protsessov kompensatsii v strukture prostranstvenno-vremennýkh otnoshenii EEG bol'nykh pri narushenii reguliatornykh mekhanizmov mozga.

Studies of intercentral relations of electrical activity in the cerebral cortex of the patients with hypophysis tumours under the conditions of chronic (before operation) and acute (after tumour ablation, early post-operative period) influence of the focus on the regulatory brain systems allowed to reveal definite changes of spectral-coherent EEG characteristics, reflecting the functional state of the cerebral adaptive-compensatory apparatus. It has been shown that reciprocal character of changes of various forms of the brain electrical activity and their intercentral relations is one of manifestations of development of the processes of cerebral compensation. At the same time, global fall of the EEG intercentral relations indicating the disintegration of the cerebral functional connections, reflects a loss of CNS compensatory mechanisms. The revealed EEG-characteristics at the present time are applied in Burdenko Institute of Neurosurgery for diagnostic-prognostic estimation of the brain functional state in patients during pre- and post-operative period.

[The reorganization of the electrical activity of the human brain during the depression of consciousness (comatose states)]. / Reorganizatsiia élektrichsekoi aktivnosti mozga cheloveka pri ugnetenii soznaniia (komatoznye sostoianiia).

To study the problem of consciousness an original structural-functional approach has been applied with the use of possibilities of spectral-coherent EEG analysis in evaluation of human brain functional state together with the specificity of the cerebral coma having local focal belonging. It is revealed that the most informative signs for characteristics of consciousness state are peculiarities of reconstruction of intercentral relations of the electrical brain processes: decrease of mean levels of the EEG coherence at progressive development of coma; staged approach to relative norm at regressive course of comatose state and recovery of consciousness; their stability on the low level at prolonged coma; increase in low or high (above optimum) frequencies band at neighbouring with coma states of consciousness. It may be considered that one of the necessary conditions of normal state of consciousness is preservation of the optimum level of correlation of electrical brain activity alongside with frequency-regional specificity of the EEG coherence spectrum. Any deviation from the optimum is unfavourable condition for normal course of cerebral reactions because of the disturbance of intercentral connections mosaic necessary for their realization.

[The organization of human EEG rhythms in special states of consciousness]. / Organizatsiia ritmov EEG cheloveka pri osobykh sostoianiiakh soznaniia.

In the paper the results are presented of studying of the electrical brain activity of a specific contingent of subjects which by subjective evaluations considered themselves a category of sensitives (extrasenses). The EEG of these subjects was studied in various functional states--a state of relative rest (background) during diagnostics, of directed influence on the percipient and during meditation. Specificity of spatial-temporal organization of the brain electrical processes of operators--sensitives was revealed, the structure of which correlated with the state of mind. The character of changes in the EEG of these subjects in the background and especially during autogenous activity allows to suggest the formation of a spontaneous focus of stimulation in regulatory brain systems with a leading role of the frontal cerebral regions in these processes as one of the ways of organization of cerebral functions for the regulation of the extrasensory activity.

[The significance of interhemispheric asymmetry in the development of compensatory processes in the human brain]. / Znachenie mezhpolusharnoi asimmetrii v razvitii kompensatornykh protsessov mozga cheloveka.

For more precise definition of the role of hemispheric interconnections in mechanisms of human CNS compensation the intercentral relations of the electrical activity of the left and right cerebral hemispheres were studied on physiological model of focal interhemispheric asymmetry. Spectral-coherent EEG characteristics of 36 patients with tumoral damage of one hemisphere were studied in condition of chronic (prior to operation) and acute (early terms of postoperative period) brain decompensation. In was shown that the reorganization of the structure of the EEG intercentral relations correlated with definite stages of CNS compensatory processes and that the character of hemispheric interconnections depended on the lateralization of the damage focus. The primary role was revealed of the degree of the left (dominant) hemisphere preservation in restoration of normal pattern of the interhemispheric asymmetry of the coherence of human brain electrical processes.

[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.

[Peculiarities of changes in the EEG in the development of coma in patients with a focal injury of the brain]. / Osobennosti ixmenii na EEG pri razvitii komy u bol'nykh s ochagovym porazheniem golovnogo mozga

A number of new electrographic variants reflecting the specifity distinguishing the evolution of coma in focal affections of the brain and clearly correlating with its clinical manifestations were elicited. The comatose status, apart from a fall of the level and frequency of the brain biopotentials, is shown to be characterized by an imbalance of spatial and temporal relations in the cortex of the large hemispheres, a correlation between the degree of disrupted inter-central relations and the stage marking the development of the comatose process having been disclosed. Some EEG findings were obtained that may be taken advantage of in judging about the prognosis as to the evolution of coma. An electroencephalographic investigation of the comatose states in focal lesions of the brain opens up the possibilities for a differential approach to the study of coma.