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Recent data on the neurophysiology and neurochemistry of sleep have led to a revision of views regarding the role of brainstem centers and basal ganglia involved in the modulation of wakefulness levels and the regulation of slow-wave and paradoxical sleep [1][2][3][4]. New data were obtained on the changes in the neurochemical activities of several precisely located deep structures of the brain, each of which is involved in the regulation of both wakefulness levels and sleep depth through periodic activation of inhibitory neurons of these structures [4]. These data confirmed that slowwave sleep plays a role in homeostasis and attracted more attention to the search for consistent patterns in the interrelations between individual cortical and brainstem regions as dependent on the depth of sleep.While considerable progress has been made in studying the neurophysiological mechanisms of natural sleep, intense studies of the hypnotic state at the new methodological level are in their infancy. It remains unknown why natural sleep and the hypnotic state are similar in some characteristics (e.g., behavioral parameters and the possibility of transition of hypnosis into sleep [5][6][7]) and are radically different in others, especially EEG parameters [8,9].The results of recent studies using positron emission tomography showed important topical characteristics of the selective activation and inactivation of cortical fields and some subcortical centers in hypnosis [10][11][12]. However, the undeniable advantages of computer tomography are still insufficient for obtaining necessary information on the changes occurring in the systemic interaction between different cerebral structures as the consciousness is narrowing.The interregional interactions of cortical biopotentials recorded in different periods of sleep also remain somewhat unclear [13][14][15]. Thus, which cortical regions change their functional relationships at different depths of natural sleep and the hypnotic state, as well as the extent of these changes, is still an open question. At the same time, detailed analysis of the patterns of cortico-subcortical integration under these conditions, taking into account the specificity of local changes in bioelectric potentials apparently determined by the modulating effect of subcortical centers, may be an effective approach not only to understanding the physiological mechanisms of the cerebral control of basic states but also to studying some important mechanisms of cognitive activity and the algorithm of retrieving trace memories.We searched for permanent characteristics of the spatial structure of the cerebral biopotential field at different stages of natural sleep and hypnosis in order to determine consistent neurophysiological patterns of the Abstract -The characteristic patterns of EEG spatial organization at different stages of natural sleep and the hypnotic state were studied in 26 volunteers aged 18-22 years. EEGs were recorded using 12 monopolar leads, and EEG cross-correlation coefficient matrices were calculate...

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The contribution of genetic factors to the formation of the neurophysiological mechanisms of cortical-subcortical integration was studied in 12 pairs of monozygotic and five pairs of dizygotic twins (aged 18-25 years). Intrapair similarity of the nature of spatial interactions between bioelectrical activity in the cerebral cortex, assessed from different combinations of statistical interactions of EEG from 16 monopolar recordings, was assessed in each pair of twins (and among 544 non-related pairs of subjects in both groups). The results suggest a high level of general population invariance and relatively small inherited and phenotypic variability in the morphofunctional systems making up the major neurophysiological mechanisms of brain integration as a whole. The ontogenetic formation of stem and subcortical regulatory structures, which have a leading role in the systems combination of different parts of the brain into a single formation, appears to occur in all individuals by the same principle, as disturbance can apparently affect the fundamental monomorphic features of the species. In turn, we might expect to find large interindividual variability in the establishment of interregional connections of the neocortex, the role of inherited and environmental factors being different in the processes forming long and relatively short intercortical interactions.

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Electropolygraphic study of natural night sleep was performed in 16 adult subjects using correla tion, coherent, cluster, and factor analyses. New evidence testifies to the active nature of sleep, which is espe cially manifest during falling asleep and transition from one stage of sleep to another. Falling asleep and deep ening the sleep proved to be accompanied by intense reorganization of the cortico subcortical relationships, which is reflected in the dynamics of cross correlative and coherent interrelationships of the brain's bioelec tric potentials. Transition from wakefulness to sleep is a heterogeneous process, which is expressed in signif icant changes in the weights of factors I, II and III of the vector image of multichannel EEG at stage I (B) of sleep, which might reflect changes in the contribution of the main integrative brain system in the reorganiza tion of the brain's integrated activity. A considerable increase in the weight of factor I (this reflects generalized the modulating effect of the brainstem on the cortex) and a decrease in the weights of factors II and III (which are related to fronto occipital and interhemispheric interactions) testify to the special synchronizing role of the brainstem in the development of this initial stage of sleep. Deeper sleep is accompanied by a decrease in inter hemispheric EEG relationships of the anterior and inferior frontal areas of the cortex, which suggests that coor dinated inactivation of the cortex in both hemispheres leads to reorganization of the activity in the frontal areas. Analysis of the average variance of cross correlative (CC) EEG relationships demonstrates that stability of the spatial structure of interrelationships between various areas of the brain cortex increases with falling asleep at stage I (A); however, during transition to stage I (B), the CC EEG values become unstable and, with deepening sleep, the variance of these values decreases in the frontal brain cortex. With the onset of the paradoxical phase of sleep, the variance of the levels of interregional interactions increases to the maximum, especially with respect to the EEG relations of the posteriotemporal and inferiofrontal areas of both hemispheres.Keywords: sleep, integrative brain activity, mechanisms for switching the stages of sleep, multiparametric EEG analysis.