S. I. Soroko

Human Systemic Reactions to a Dosed Exposure to Hypoxia: A Multiparameter Study

Human physiological reactions to acute hypoxic hypoxia were studied. Analysis of simultaneously recorded parameters of various physiological systems showed the following: activation of the general antihypoxic defense system is based on the formation of an intricate structure of intra- and intersystemic relations of specific and nonspecific elements of adaptation that support vital body functions during environmental oxygen deficit. These specific elements become more important in more severe hypoxia, which suppresses metabolism in some organs and tissues because of redistribution of blood flow. These factors allow the body to function at a lower oxygen tension in its tissues owing to an increased efficiency of mitochondria as a result of changes in the kinetics of enzymes of the mitochondrial respiratory chain. In acute hypoxia, the structure of intra- and intersystemic relations is rather intricate; its functional hierarchy is maintained by stronger individual amplitude-related controlling factors and by modulation of their phase- and time-related links. Advanced stages of hypoxia are associated with disintegration of central regulatory mechanisms, which is manifested by disturbances in amplitude-frequency and spatiotemporal parameters of the brain bioelectrical activity, changes in phasic interactions between elements of regulatory mechanisms, and signs of deregulation and decompensation of vital functions. The interpretation of the results is based on the general theory of adaptation, Medvedevs idea of adaptation as a successive involvement of genetically predetermined and newly-formed regulatory programs of the brain, Anokhins theory of functional systems, and modern concepts of molecular and biochemical mechanisms of hypoxia. It was concluded that artificial normobaric hypoxia is a unique, biologically adequate model that makes it possible to study the rearrangements in systemic and autonomic regulatory mechanisms in response to strictly determined changes in the environmental concentration of oxygen as a principal factor supporting life.

Psychophysiological and cardiohemodynamic effects of solar, geomagnetic, and meteorological factors in humans under the conditions of the arctic region

The influence of variations in solar, geophysical, and meteorological factors, as well as of the lunar cycle phases, on cardiohemodynamic, emotional and CNS parameters has been studied in 12 men (19–38 years old) permanently residing in the Arctic region (the town of Apatity, 67°57′ N, 33°39′ E). The period of observation was characterized by M1 and M2 class solar flares and G1-G3 class geomagnetic storms. The study has demonstrated the adaptive modulation effects of environmental factors on autonomic regulation systems and the perturbing influences of geomagnetic storm and solar chromospheric flares on human functional state. Multiple regression analysis was used to identify the dominant environment factors by the degree of their influence on functional parameters and to assess their combined effect. The coefficient of determination was no more than 0.5 on average; however, in some subjects, it reached 0.7–0.8 for certain parameters. All subjects were shown to respond to the permanent fluctuations of climatic-geographical and cosmophysical factors under the extreme conditions of high latitudes; however, response pattern and intensity depended on individual sensitivity to their isolated and combined effects.

EEG Correlates of Genophenotypic Characteristics of Brain Development in Children of the Aboriginal and Settler Populations in Northeast Russia

Traditional and original analytical methods were used to study the developmental characteristics of EEG dynamics in 156 children and adolescents aged 7–17 years of the aboriginal (Koryaks, Evens) and offspring of settler (Europeoid) populations living in the severe climatogeographical conditions of the northeast of the Russian Federation. New data were obtained on the age- and gender-related and ethnic characteristics of the formation of brain bioelectrical activity. EEG markers were identified characterizing changes in the structure of interactions between EEG rhythms. Developmental rearrangements of this structure were found to occur at different times for different cortical areas and frequency ranges, with onset 2–3 years later in children of the aboriginal population than in offspring of the settler population. It is suggested that these differences reflect the genophenotypic characteristics of the morphofunctional development of the CNS in children of the aboriginal and settler populations on the background of increased adaptive pressure in extreme environmental conditions.

Age dynamics of evoked brain potentials in involuntary and voluntary attention to a deviant stimulus in schoolchildren from the northern region.

The central mechanisms of involuntary and voluntary regulation of attention in schoolchildren from the northern region were studied using a method based on the P300 wave of evoked brain potentials (the oddball paradigm). Data were compared with results obtained from psychological tests. Differences in the organization of EP were seen in the “passive” and active (counting) perception of deviant stimuli. Three components were identified within the time envelop of the P300 wave, two of which dominated in the frontal and one in the parietal area of the cerebral cortex. The latency of the P300 wave decreased with age in the children, reflecting increased rates of information processing and increases in the volume of operative memory. In passive perception, the statistical relationship characterized by a reduction in P300 latency with age was significant for leads in the central, temporal, parietal, and occipital areas; in active perception, this applied to all areas including the frontal. The most significant changes in P300 parameters were seen in children aged from seven to 12 years, indicating that this period can be regarded as “critical” in the development of learning skills. The roles of the parietal and frontal areas of the cortex in the mechanisms of involuntary and voluntary regulation of attention are discussed, along with the possibility of using the P300 method to identify children with delayed rates of development of voluntary attention in population studies.

Individual strategies of human adaptation under extreme conditions

Starting from the investigations of Sechenov, Pavlov, and Uchtomsky, the Russian psychophysiological school has been considering adaptation in connection with the biological and social origin of the person (human as a rational being) as an integrated, coordinated, and self-controlled system. On the basis of the problem of man and the environment, Medvedev added to the theory of human adaptation the activity paradigm that enables us to uncover the distinctive features of occupational activities under various environment conditions. The theoretical and practical investigations based on the activity methodology presented the opportunity to find new principles of interaction between man and the environment and of the strategy of adaptive behavior. From the investigations one could see that the main characteristic of the human-environment interaction is that the active factor is the human who could simulate different adaptation strategies.

Formation of the Interaction between the Wave Components of the Main EEG Rhythms in Children up to Five Years of Age

Using the analysis of the interaction between EEG components [1], the authors studied the regularities of the formation of the EEG wave structure in 36 children aged 4 to 7 months, 2 to 3 years, and 4 to 5 years. The EEG of 4- to 7-month-old children had a relatively organized temporal structure, whose components were connected mainly with those of the slow-wave range. This structure is reproduced in most of the leads and is more stable in the anterior cortical areas than in the posterior ones. The waking 2- to 5-year-old children had two “functional” nuclei in the relation structure of the EEG components characterized by statistically significant enhancement in the probability of the consecutive appearance of waves of certain ranges. These nuclei include a slow-wave nucleus in the range of the Δ2–θ1-frequencies and an “alpha”-nucleus in the α1- and α2-ranges (θ2 and α1 2- to 3-year-old children) of the EEG frequencies. The relations between the components of the slow-wave nucleus begin to form in infants, prevail in 2- to 3-year-old children, and weaken by the age of 4 to 5 years. A trend is observed in 2- to 5-year-old children towards an increase in the average frequency of the waves that form the slow-wave nucleus. The temporal (strengthening interaction between the waves) and spatial organization of the interaction between the wave components of the “alpha”-nucleus is accelerated at the age of 4 to 5 years. The average frequency of the components forming this nucleus gradually increases with the childrens age from 4 to 7 months to 4 to 5 years. Competitive relations exist between the two nuclei, characterized by a significant decrease in the probability of transitions between the components of different nuclei. The θ2-component may play a special role of the connecting link between the nuclei at the age of 4 to 5 years, the interwave transition from the Δ- to θ-frequencies and from the latter to the α-range being effected by a leaplike rather than smooth frequency increase. The character of local and spatial rearrangements of the EEG temporal structure detected in this study reflects a gradual morphofunctional maturation of the brain as a system that maintains the specific features of self-regulation mechanisms and coordination of the intersystem interactions at various stages of a childs development.

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.

Passive perception of auditory stimuli in healthy and mild mentally retarded adolescents from Northern Russia

Event-related potentials (ERPs) during passive perception of auditory stimuli were studied using the oddball paradigm in healthy and mild mentally retarded adolescents. The study involved 25 subjects aged 11–15 (13.1 ± 1.4) years from Northern Russia, including Arctic regions. The peak latency of the difference wave for deviant and standard stimuli in frontal central derivation was 129 ± 21 ms in the healthy children, and the mean amplitude was–2.6 ± 1.3 μV. In the mentally retarded group, a negative peak of the difference wave was observed only in 9 out of 13 adolescents, its latency was more than in the healthy adolescents (156 ± 29 ms), and the mean amplitude was–2.1 ± 1.4 μV. Differences in perception of deviant and standard stimuli were observed in the healthy adolescents, in particular, along the central line. In the adolescents with mental disorders, there was no significant difference in the fronto-central and central derivations. A discriminant analysis of the amplitudes of ERP components observed in the fronto-central derivations in response to deviant stimuli and the difference in amplitude between ERPs evoked in the fronto-central derivation by standard and deviant stimuli differentiated the adolescents with and without mental disorders. Based on the findings, ERP components in the oddball paradigm were assumed to provide potential markers of disorders in mental development.

Age and gender features of the content of macro and trace elements in the organisms of children from the European North

The content of 28 macro and trace elements (Al, Ag, Li, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, K, Mg, Mn, Na, Ni, Mo, P, Zn, Se, Tl, Pb, Sr, S, and Si) in the hair of children and teenagers living in the European North of the Russian Federation (Arkhangelsk oblast) was studied by atomic emission spectrometry with inductively coupled argon plasma. Both a decrease and an increase in the content of certain elements were detected. The dynamics of the content of the above-mentioned elements in the hair of the same children in different years was traced. Significant individual variability of macro- and trace element status of northern children and certain gender dependence was revealed.

Parameters of cerebral blood flow of 7- to 11-year-old children living in northern European Russia

Doppler sonography and rheoencephalography were used to study cerebral hemodynamics of young schoolchildren in the village of Klimovskoe (Konosha raion, Arkhangel’sk oblast, Russia). Mean linear blood flow velocities (LBVs) in the major cerebral vessels did not differ significantly from the velocities measured in age-matched children living in St. Petersburg. The index of resistivity was lower in the residents of the North than in their counterparts in St. Petersburg, which suggests a decreased tone of resistive vessels of the children living in the North. Asymmetry of the LBVs through the homonymous cerebral arteries of the left and right hemispheres was found in 67% of children examined. Asymmetry of the LBVs in the anterior, middle, and posterior cerebral and vertebral arteries (VAs) was correlated with a malformed posture (such as scoliosis or a slouch). In most children examined, sideward head rotation was accompanied by compression of VAs at the level of the C1 and C2 cervical vertebrae; in 71% of them, this condition could be regarded as a hemodynamically significant stenosis. In all children, a decreased LBV observed in one of the VAs was completely compensated by an increased LBV in its contralateral counterpart. Doppler sonographic signs of dystonic VAs and/or asymmetrical LBVs in the VAs were found in 79% of children examined. These children can be supposed to have latent disorders of blood flow in the VA basins caused by vertebral influences (related to irritation of the periarterial nervous plexus or cervical autonomic plexuses). The schoolchildren living in the North exhibited a lower reactivity of their cerebral vessels to hypo-and hypercapnia than their counterparts living in the central parts of the Russian Federation or in St. Petersburg. Regional differences were found in the sensitivity of cerebral vessels to hypocapnia. The volume of blood in the basins of the internal carotid arteries determined in a hypocapnic test was decreased; it was increased in the basins of VAs. This fact can be interpreted as a regional redistribution of the cerebral circulation caused by extreme environmental factors stimulating vital regulatory sites of the brainstem.