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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...