[Features of brain biopotentials' spatial organization in adolescents].

Adolescence is characterized by an intensive formation of inter-regional cortical fields interaction, in this period significantly reorganized the activities of deep brain structures and cortical-subcortical interaction are enhanced. Our objectives were to evaluate the nature of changes in the spatial organization of brain bioelectric potentials with age and characteristics of such an organization in adolescents. For this purpose, EEG studies have been conducted in 230 subjects of both sexes aged 4 to 35 years. We estimated interdependent changes of biopotentials correlations fluctuations in 20-lead EEG, using the integral index Vol. Analyzed age-related changes of EEG correlations in rest condition and during verbal activity (Russian and English texts audition). Verbal tasks were sued in subjects over 8 years. It was found that the spatial synchronization of the EEG both in background and verbal activity increases with age, but after 20 years the rate of change is significantly reduced. In adolescence (12-17 years old), sex differences appear between the degree of EEG coherence processes occurring in the left and right hemispheres in subjects performing verbal tasks. In males 12 to 14 years nonlinear changes in overall correlation (indicators VOL) was observed, whereas in females of this age systemic reorganization of the brain interrelations occurs more smoothly, ahead of 1.5-2 years.

["Microcyclic" changes in brain bioelectrical activity during different stages of human natural sleep].

This study presents data on some phasic EEG phenomena regulary recorded during sleep - wakefulness cycle and heterogeneity of EEG sleep stages forming consecutive human sleep macrocycles. These short-term EEG changes quite often tend to periodization, especially during initial sleep-stages and transitive states (sleep microcycles). An attempt was made to reveal EEG microstructures in sleep - wakefulness cycle on the basis of 7 clusters reflecting changes in the biopotential field of the brain represented in n-dimensional factorial space. It was found that most sleep stages were presented by 3-4 clusters, but some sleep periods (such as B (Loomis, 1937) and IREM) showed more homogeneous structure. It was suggested that the heterogeneity of the EEG spatial organization within sleep stages reflect the dynamics of neurophysiological processes underlying reparative and homeostatic sleep functions.

[Unusual behaviors in sleep as "compensatory" reactions, aimed at normalizing sleep-alertness cycles].

The present article is an attempt to perform a conceptual clinical and physiological analysis of a large spec- trum of sleep-related phenomena called parasomnias in children, based on data from three independent in- stitutions. Parasonmias appear in the process of falling asleep, at the time of sleep stage changes, and upon awakening. They are common for both healthy children and those with neurological and psychiatric disorders. Brief descriptions of clinical pictures of several groups of parasomnias and their polysomnographic characteristics are presented. Instances of stereotyped rhythmic movements (e.g. head rocking), paroxysmal somatic and behavioral episodes (night terrors and nightmares), "static" phenomena (sleep with open eyes, strange body positions), as well as somnambulism are specifically described. Common features of parasomnias as a group have been identified (the "Parasomnia syndrome"). It was found that sleep architecture frequently normalizes after a parasomnia episode, whereas parasomnias are self-liquidated after sleep matures (self-cure). The significance of gender differences in parasomnias have been reviewed. Possible compensatory physiological functions of parasomnias acting as "switches" or "stabilizers" of sleep stages to "off-set" deviated or immature sleep-wake mechanisms were discussed.

[The features of system organization of the brain activity during different sleep stages and transition states].

Electropoligraphical study of the natural night sleep in 16 adults with the use of correlation, coherent, cluster and factor analysis were used to obtain new data describing the active nature of sleep, which is expressed especially in periods of falling asleep and the transition from one stage to another. It is shown that the process of falling asleep and deeper sleep is accompanied by intense reorganization of cortico-subcortical relations, which is reflected in the dynamics ofcrosscorrelation and coherent estimates of interrelations of biopotentials of the brain. The results of factor analysis of multichannel EEG heterogeneity of the transition process from wakefulness to sleep is manifested in significant changes of I, II and III factors weight during I(B) stage of sleep, which may reflect changes in the degree of contribution of the main integrative brain systems in the reorganization of its integral activity. A considerable increase in the I factor weight (reflecting the generalized modulatory brainstem effect on the cortex), along with a decrease in the balance of factors II and III (associated with organization of fronto-occipital and interhemispheric interactions) clearly indicates a special role of sleep synchronizing influences from the brain stem in the development of this initial stage. Reduction of EEG interhemispheric interrelations in the anterior and inferior frontal areas with the deepening of sleep may be indication of the reorganization of the frontal areas activity associated with the coordinated increasing of inactivation process in the cortex of both hemispheres. Degree of stability of the spatial structure of interregional interactions of different brain cortex areas (according to the analysis of average dispersion of crosscorrelation EEG relations) increases on falling asleep with the onset of stage I(A), but with the transition to the stage I(B) there is a significant increase of instability of values EEG crosscorrelation. With the deepening of sleep the subsequent decrease of the dispersion of EEG crosscorrelations in frontal cortex is revealed. During REM sleep the dispersion levels of inter-regional interactions increases as much as possible, especially for EEG crosscorrelations of posterotemporal and inferiofrontal parts of both hemispheres.

[Features of cortex areas system interactions in the left and right brain hemospheres during different human sleep stages].

The article is devoted to analysis of research brain biopotential field structure during different stages of natural night sleep in adults. The special attention is given to distinctions of the spatial organization of EEG interregional relations in the left and right hemispheres which are shown most strongly in the II and III sleep stages. The special role of frontal cortical areas in reorganization of brain system activity during falling asleep is highlighted. Essential strengthening of hemispherical interaction of cortex biopotentials fluctuations during falling asleep--a stage of I(B)--along with its reduction in central and occipital cortical areas is shown during a slow wave sleep (II--IV stage) versus wakefulness.

[On factors that effect the variability of central mechanisms of bilingualism].

The article discusses the probable role of many factors that determine the individual variety of neurophysiological mechanisms, which provide the opportunity to learn and free use two or more languages. The formation of a speech functions is affected by both the general factors for bilinguals and monolinguals, as well as the specific characteristic of the situation of bilingualism. The general factors include genetic and environmental impact of explaining the diversity of individual options for the development of morphofunctional organization of speech functions. A bilinguals, obviously, have even more wide variance of the central maintenance of speech activity, due to the combination of different conditions that influence the language environment, which include the age of the second language acquisition, the language proficiency, linguistic closeness of the languages, the method of their acquisition, intensity of use and the scope of application of each of the languages. The influence of these factors can mediates in different ways by the individual characteristics of the bilingual's brain. Being exposed to two languages from the first days of life, the child uses for the development of speech skills of the unique features of the brain, which are available only in the initial stages of postnatal ontogenesis. In older age mastering a second language requires much more effort, when, as maturation, the brain acquires new additional possibilities, but permanently lose that special "bonus", which nature gives a small child only in the first months of life. Large individual variability patterns of activation of the cortex when verbal activity in late bilingual" compared with the "early", allows to assume, that the brain of "late bilingual", mastering a new language, forced to operate a large number of backup mechanisms, and this is reflected in the increase of variation in the cerebral processes, responsible for providing of speech functions. In addition, there is serious reason to believe that learning a second language contributes to the expansion of the functional capabilities of the brain and creates the basis for a successful cognitive activity.

[Peculiarities of disorders of brain bioelectrical activity spatial-time organization in patients with different consciousness depression after severe head injury].

Specific changes of bioelectrical brain activity was found in 27 patients with different level of posttraumatic consciousness depression by the methods of crosscorrelation, coherence and factor analysis of EEG. The changes of activity of morphofunctional systems of intracerebral integrations were revealed partially by decreasing of unspecific activity from brainstem structures reflected with increasing of slow wave activity and decreasing of EEG coherence in alpha- and beta-range. Depression of system organization of interconnections of bioelectrical brain activity in frontal and occipital regions of both hemispheres was also detected, and testified about decreasing of intercortical and thalamocortical brain system action under brain dislocation. The changes of integrative brain system activity, provides interhemispheric interaction, had the specific characted. Our results propose a "facilitation" of activity of system, providing "direct" interhemispheric connections through corpus callosum and other commissural tracts of telencephalon as a sequel of mesodiencephalon structures depression with steady reciprocal, antiphase relations of slow weve activity in symmetrical areas of hemispheres in coma II patients. The data of our research had shown no complete disintegration of system brain activity in coma II patients in spite of consciousness and brainstem reflexes depression.

[About a possible role of parasomnia as a factor of stabilization of sleep cycles].

Cyclical organization of sleep is one of necessary conditions of normal human and animal life activity and one of basic manifestations of the circadian cycle. Transition from the slow-wave to the paradoxical sleep is often accompanied by brief, sometimes rhythmical motor and autonomic reactions that do not cause arousal, but seem to promote activation of the mechanisms providing the "shift" of the sleep phases. Immaturity (or damage) of the neurophysiological mechanisms responsible for the "shift" of the sleep stages leads to hindering of alternation of the sleep phases, which disturbs their normal sequence and leads to deficit of reparative and homeostatic processes; this is manifested in deterioration of the neuropsychical state during wakefulness. The data are presented which allow suggesting that as a compensatory mechanism promoting the sleep phase shift there can appear stereotypical motor or autonomic reactions - pathological parasomnia, for instance, enuresis. Episodes of the pathological parasomnia promote normalization of the sleep stage alternation and thereby affect positively recovery of its cyclical organization.

[Analysis of the spatial-temporal EEG organization as the way to the knowledge of neurophysiological mechanisms of the integrative brain activity].

Short results' review of investigations of Laboratory of Neurophysiology of Child of Sechenov Institute is presented in the article. Investigations are based on concept of academic M.N. Livanov about special role of spatial-temporal relations of brain potentials oscillations of various brain areas in providing of functional connection between them. It is shown, that in rest condition the structure of interregional relations of cortex biopotentials in all healthy people is characterized by high spatial orderliness that obviously assists to optimal realization of informational processes during various functional conditions from rest to complex cognitive functions. Special attention is given for the problem of functional signigicance of phase shifts of EEG waves. Data, that allows concluding that brainstem and thalamocartical integrative systems are characterized with relatively small inherited and phenotypic variability whereas fiber systems of both hemispheres that provide processes of intercortical integration are characterized by more expressed inter-individual variability, is presented. Intensive development of long associative and commissural tracks of telencephalon that joined even the most distanced cortical regions of hemispheres in united formation apparently results in formation of morpho-functional "skeleton" of neocortex, that occurred to be the basis for origin of qualitatively new (in comparison to animals) principals of formation of system organization of integral activity of the brain. Existence of long mono- and oligo-synaptic connections provides conditions for correlative develoment in ontogenesis of new function that is not conditioned by phylogenetic development.