[ESTIMATION OF THE EFFECTS OF GEOMAGNETIC AND SOLAR ACTIVITY ON THE HUMAN BRAIN BIOELECTRICAL PROCESSES WITH STRUCTURAL FUNCTION].

We investigate the impacts of sharp variations in solar and geomagnetic activity (GMA) at high latitudes on the human brain bioelectrical activity by means of the empirical structure function of multi-channel EEG. Ten healthy men ages 19 to 37 took part in the study. EEG was recor- ded daily over the 25 days test period that was marked by C- and M-class solar flares and geomagnetic storm levels in the G2-G3 range. The EEG signals were used for the estimate of the mul-tivariate temporal structure function (SF) of the first order in 8-dimensional space. The value of the SF correlation radius is used here as an estimation of a scale of the integral temporal correlation structure of multi-channel EEG, while the value of the SF horizontal asymptote is used as an estimation of the spatial correlation structure of EEG. It is shown that GMA variations make an even greater impact on the SF correlation radius, than on the SF asymptote. We reveal the disturbing and modulating effects of geomagnetic and solar activity on the SF parameters and its power spectrum. Thus, the SF of multi-channel EEG allows us to estimate the effects of heliogeophysical factors on the integrated brain reaction as a unitary system and may be used to investigate the environmental influence on the humans.

[General Features of the Formation of EEG Wave Structure in Children and Adolescents Living in Northern European Russia].

The article presents the results of the analysis of EEG wave structure formation in children and adolescents aged 7-18 years living under severe conditions of the North. The approaches developed in discrete mathematics (the graph theory, the theory of network flows) were used to assess the time-frequency transformations of EEG patterns. We evaluated conditional probabilities of reciprocal transitions between the components of six frequency bands of E EG (delta, theta, alpha-1, alpha-2, beta-1, beta-2). We described age- and sex-related features as well as regional specificities of the EEG wave structure. We defined the age periods of reorganization of diffuse EEG activities into the main EEG rhythms; the role of distinct rhythms in the maintenance of the EEG wave structure and its dynamic rearrangements was also discussed. The age-related changes of the structure of EEG patterns form some general picture of the morphofunctional development of brain in children and adolescents at different stages of postnatal ontogenesis under severe climate and socio-economic conditions of the North.

Longitudinal study of EEG frequency maturation and power changes in children on the Russian North.

The aim of the study was to reveal longitudinal changes in electroencephalogram spectral power and frequency (percentage frequency composition of EEG and alpha peak frequency) patterns in normal children from northern Russia. Fifteen children (9 girls and 6 boys) participated in the study. The resting state (eyes closed) EEGs were recorded yearly (2005-2013) from age 8 to age 16-17 for each child. EEG frequency patterns were estimated as the percentages of waves with a 1 Hz step revealed by measuring the interval durations between points crossing zero (isoline) by a curve. EEG spectral power changes were analyzed for delta (1.5-4 Hz), theta (4-7.5 Hz), alpha-1 (7.5-9.5 Hz), alpha-2 (9.5-12.5 Hz), beta-1 (12.5-18 Hz) and beta-2 (18-30 Hz) bands. According to the frequency composition of the EEG signals fast synchronous, polymorphous synchronous, polymorphous desynchronous and slow synchronous types of children EEG were revealed. These EEG types were relatively stable during adolescence. In these EEG types, the frequency patterns and spectral power dynamics with age had several common and specific features. Slow wave percentage and spectral power in the delta band remarkably decreased with age in all groups. Starting from the theta band the EEG types were characterized by different EEG spectral power changes with age. In fast synchronous EEG type, the theta and alpha-1 EEG power decreased, and the alpha-2 power increased in the occipital and parietal areas. The polymorphous synchronous type was characterized by increased both the alpha-1 and alpha-2 power with regional peculiarities. In the polymorphous desynchronous type spectral power in all bands decreased with age, and in the slow synchronous type, the alpha-1 power massively increased with age. Obtained results suggest predictive strength of the spatial-frequency patterns in EEG for its following maturation through the years.

[Features of seasonal reorganizations of the central mechanisms of regulation in children northerners with different level of social risk].

The paper presents a comparative analysis of frequency, spatial-temporal parameters and three-dimensional localization of EEG sources that characterize changes of cortical-subcortical interactions processes in autumn and spring periods at northern schoolchildren living in satisfactory and disadvantaged (risk group) conditions of the social (family) environment. Seasonal rearrangement of interaction between wave components of main EEG rhythms was revealed. School students present regressive changes in the EEG pattern temporal organization in spring compared to autumn, and this effect was more expressed at adolescents from group of risk. Data EEDS-tomography showed increased activity in the prefrontal, cingular and subcallosal areas of the cortex in the autumn period that could be related to the mechanisms of season depression caused by the significant reduction of the day length in the North. The increased activity of the limbic system structures which is persisted in the spring in adolescents from risk group narrows the range of regulation of adaptive reactions. Unfavorable conditions of the family environment are an additional stress factor to increased load on the regulatory mechanisms that have a negative impact on the emotional-motivation behavior of children and adolescents, thus increasing the risk of the school and of social disadaptation.

[EEG correlates of geno-phenotypical features of the brain development in children of the native and newcomers' population of the Russian North-East].

Traditional and original methods of EEG analysis were used to study the brain electrical activity maturation in 156 children and adolescents from 7 to 17 years old who represented the native (Koryaks and Evenks) and newcomers' populations living in severe climatic and geographic conditions of the Russian North-East. New data revealing age-, sex- and ethnic-related features in quantitative EEG parameters are presented. Markers are obtained that characterize alterations in the structure of interaction between different EEG rhythms. The results demonstrate age-dependent transformation of this structure separated in time for both different cortical areas and different EEG frequency bands. These alterations show time lag from 2 to 3 years in children of native population compared to the newcomers. The revealed differences are assumed to reflect geno-phenotypical features of morpho-functional CNS development in children of the native and newcomers' population that depend on strong adaptation tension for extreme environmental conditions.

[Individual systemic reactions of human organism under acute hypoxia].

Results of physiological and biochemical study including analysis of brain electrical activity dynamics, volumetric and linear parameters of cerebral blood flow, plasma stress hormones levels (adrenaline, noradrenaline, cortisol) and energy metabolism markers (glucose, lactate) at different stages of acute normobaric hypoxia are presented. The correlations are shown between alterations of main cerebral arteries tone and resistivity type vessels, as well as between changes in linear and volumetric cerebral blood flow providing a compensation of the oxygen deficit. Features of EEG dynamics were investigated that characterized CNS regulatory functions and brain electrogenesis disturbance under deep stages of hypoxia. By means of original evaluating methods of interaction structure between different EEG rhythm, EEG markers were obtained that revealed both brain intercentral interaction rearrangements and functional disintegration of systemic brain activity at various stages of acute hypoxia.

Cortical-subcortical interactions and the regulation of the functional state of the brain in acute hypoxia in humans.

The mechanisms regulating the functional state (FS) of the brain were studied in humans in conditions of dosed acute hypoxia (breathing a mixture of 8% oxygen in nitrogen for 15-25 min). The dynamics of the FS of the brain due to changes in the balance of the activities of brain regulatory structures in hypoxia were reflected in rearrangements of EEG spatial relationships (factor and cluster analysis of EEG crosscorrelation matrixes) and the redistribution of intracerebral locations of electrically equivalent dipole sources (EEDS), with increases in EEDS density in the projections of the medial and basal parts of the temporal lobes of the hemispheres (EEDS tomography data). Changes in cortical-subcortical interactions were characterized by a decrease in the tone of the activatory brain system, a decrease in the inhibitory control of subcortical structures by neocortical formations, and activation of limbic system and hypothalamic structures. Switching of the integrative regulatory mechanisms from the cortico-thalamic level to the limbic-diencephalic level may allow release of the energy-consuming nonspecific components of hypoxic stress and more stable regulation of physiological parameters by the major vital systems in conditions of increasing oxygen deficit.

[Cortical-subcortical interactions and the brain functional state regulation under acute hypoxia in man].

Regulation mechanisms of the brain functional state (FS) were studied in man during acute hypoxic conditions (inhalation of 8% O2 hypoxic air for 15-25 minutes). Changes in balance of the brain regulatory structures activities caused by hypoxia determine FS dynamics that is reflected in the reorganization of the EEG spatial interrelations (by data of factor and cluster analysis of EEG cross-correlation matrices), as well as translocation of intracerebral position of electrical equivalent dipole sources (EEDS) coupled with EEDS density rising in medial and basal regions of the cerebral hemisphere temporal lobes (by EEDS-tomography data). Alterations of the cortical-sub-cortical interactions show a decline in the brain activating system tone, a decrease in the neocortical inhibitory control of subcortical processes, and activation of structures of limbic and hypothalamic regions. Switching of integrative regulatory control mechanism from "cortical-thalamic" system level to "limbic-dyencephalic" one could ensure both removal of powerful unspecific components of hypoxic stress and a greater stability of essential physiological parameters of the main vital functions regulation during oxygen deficiency accumulation.

Characteristics of the formation of systems activity in the brain and autonomic functions in children in conditions of the European North (discussion paper).

Results obtained from complex medical-physiological investigations performed during 10 scientific expeditions in the Arkhangel'sk Region in 2003-2005 are presented. The effects of climatological-geographic, biogeochemical, and social conditions of the conditions obtaining in the Far North region of Russia on sexual maturation, formation of the structural-functional organization of the brain, autonomic functions, and immunological and biochemical status of schoolchildren were studied using state-of-the-art neurophysiological methods (computerized electroencephalography, computerized rheoencephalography, computerized electric dipole origin tomography, etc.), psychophysiological and psychometric methods (assessment of the state of cognitive and memory functions, Wechsler intellectual scale), along with biochemical assay of monoamine oxidase (MAO, the key enzyme in adrenergic neurotransmitter metabolism) and the liver enzyme butyrylcholinesterase (BuChE) and physicochemical analysis of the levels of macroelements and trace elements in the body.

[Characteristics of the brain system activity and vegetative function formation in children under conditions of the European north (a problem study)].

Results of complex medical-physiological research performed during 10 scientific expeditions in Arkhangelsk region in 2003-2005 are presented. Influence of climatic-geographic, biogeochemical and social conditions of North-West region of Russia on sexual maturation, formation of the brain structural-functional organization, vegetative functions, immunological and biochemical status of schoolchildren was studied with the aid of modern neurophysiologic (computer electroencephalography, computer rheoencephalography, computed electric dipole origin tomography, etc.), psychophysiological and psychometric methods (evaluation of cognitive and mnestic functions, Vechsler 1Q estimation), biochemical assessment of monoamine oxidase and butyrylcholinesterase activity, physical-chemical analysis of macro- and microelements in the organism.

[EEG pattern as an instrument for evaluation of neurophysiological mechanisms underlying adaptation disorders].

The method of statistical evaluation of probable interaction between the main constituents of bioelectrical activity of the brain (BEA) enables to reveal the character of intercentral relations both under normal conditions and at adaptation disorders of different severance. Several types of statistic interactions have been revealed between EEG components (SSIC) correlating with normal interrelations between cortex and subcortex, level of preferential involvement of non-specific brain formations (cortex, thalamic, hypothalamic and brain-stem) into the process, and the degree of instability of neuro-dynamic processes. The findings obtained have shown the degree of expression of adaptation disorders to be connected with gradual destruction of "functional nuclear" within alpha-range, amplification of statistical interrelations with beta-EEG and teta-EEG components and formation of pathological nuclear structures within the ranges aforesaid.

[Electrical activity of the brain of children with cerebral palsy and the formation of motor skills using methods of functional bioregulation]. / Elektricheskaia aktivnost' mozga detei s tserebral'nymi paralichami pri formirovanii dvigatel'nogo navyka priemami funktsional'nogo bioupravleniia.

The authors consider the results of a quantitative and qualitative analysis of the bioelectrical brain activity in 175 children aged 5 to 14 years with motor disturbances due to various causes who received a rehabilitative treatment in a specialized child sanatorium. In addition to the traditional methods the authors employed some functional bioregulation techniques. A clinico-physiological analysis was conducted with the help of original evaluation scales. The use of the proposed method for the assessment of clinical efficacy and the employment of mathematical processing of EEG showed a high efficiency of techniques of the purposeful correction of motor disorders and contributed to a better understanding of the mechanisms of readjustments occurring in the CNS in the process of the formation of new motor skills. It was found that alpha-rhythm played the main role in the development of new motor skills.