Vol 43, No 2 (2017)

The cortical formations of the brain involved in visual functions (the occipital and temporo-parieto- occipital areas, the oculomotor area of the prefrontal cortex), as well as the motor cortex in the representation zone of the arm and the medial region of the frontal cortex adjacent to the limbic lobe, were studied in post-mortem material. The thickness of the cortex and cortical layer III, the sizes of pyramidal neurons, the specific volumes of neurons and intracortical vessels were studied in subjects of both sexes, from birth to the age of 20 years, at yearly intervals (103 observations) using histological techniques, computer morphometric and stereological analysis. The thickness of the cortex of the cerebral hemispheres was observed to intensively increase from birth to the age of 3 years in the occipital, temporo-parieto-occipital and prefrontal cortical areas involved in visual recognition processes. The increase in thickness of the cerebral cortex continues until the age of 6 in the occipital cortex and in the oculomotor area, until the age of 7 years in the temporo-parietooccipital area and the medial prefrontal area, and until the age of 8–9 years in the motor cortex. The sizes of pyramidal neurons increase until the age of 6 years in the motor cortex, until the age of 8 years on the medial surface of the frontal lobe, and until the age of 9–10 years in the temporo-parieto-occipital area and in the dorsolateral area of the prefrontal cortex. The specific volume of neurons and blood vessels in the cortex of the cerebral hemispheres decreases and the volume of intracortical fibers increases throughout the ascending ontogeny, which is manifested most intensively in the prefrontal cortex.

This article analyzes heart rate variability (HRV), the glucocorticoid function of adrenal glands, and brain electrical activity (EA) in children aged 9 to 12 years to study their functional state during early stages of puberty. The cognitive load (mental arithmetic) caused low-frequency waves in the heart rate spectrum in all subjects, regardless of the puberty stage and gender. With respect to the age range under study, the hormonal response to the arithmetic test, expressed in a decrease in the level of cortisol, was observed in boys only at the third stage of puberty. The visual analysis of the background electrical encephalogram showed frequent generalized bilateral and synchronous changes in the electrical activity (EA) in the form of diencephalic signs in children. The features of the relationship between the autonomic nervous system and the hypothalamic pituitary-adrenal system have been revealed in children aged 9 to 12 years during cognitive load. The closest correlations between HRV indices and cortisol levels have been found in girls at the first stage and boys at the third stage of puberty.

We determined the independent factors that reflect the fundamental characteristics of the functional state (FS) in adolescents aged 13–14 years (n = 162): the sympathetic regulation and parasympathetic regulation of FS, physical working capability; the efficiency of cognitive performance; the hemodynamic basis of cognitive activity; nonspecific resistance to upper respiratory tract infections. Using the systematic approach, we investigated the physiological basis of these factors and determined the indices suitable for estimating the FS of adolescents at different stages of puberty. We observed progressive dynamics of FS parameters related to factors listed above in boys of the same chronological age at different puberty stages. Beginning from stage II to stage IV, we observed a heterochronic and nonlinear decrease in the tension of system of autonomic FS regulation, an increase in the efficiency of cognitive activity and its hemodynamic supply, as well as an improvement of anaerobic working capability.

We studied the age- and sex-related functional characteristics of the central nervous system (CNS), cardiovascular system (CVS), lability of the visual sensory system, and mental capacity before and after a continuous computer work for 15 min in children aged 7, 8, 9, and 10 years. The results of the research showed that the resistance of the physiological systems of the body to loads associated with computer work increases in primary school children with age. We also observed sex-related differences: many parameters of functional performance during computer work at the age of 8 years were better in girls than in boys, which was due to a higher rate of development; at the age of 10 years, girls had a larger number of adverse changes in the functional state of the body compared with boys, which is possibly due to the onset of puberty.

The hemodynamic (magnetic resonance imaging, fMRI, 3T) brain responses were studied in 15 left-handed healthy subjects performing active and passive movements of the dominant and non-dominant hands. Group and individual fMRI responses to the motor load were analyzed. It was found that, during the active movements of dominant and non-dominant hands, the main activation cluster appeared in the preand postcentral gyrus of the contralateral hemisphere and which topographically similar during active and passive movements. The activation cluster of greater volume was identified in these areas; the response was more diffused during the non-dominant hand movements in comparison with the dominant hand. During passive movements, the cortical activation clusters of a smaller volume in comparison with the active movements were found, which was expressed most clearly during the performance of non-dominant hand movements and could reflect the weakening of the control from the cortical structures in these conditions.

We performed computer simulation and visualization of blood flow in the left ventricle by the method of smooth particle hydrodynamics (SPH). This visualization qualitatively describes the evolution of twisted stream and graphically demonstrates the direction of velocity field at each moment of time. The geometrical features of the left ventricle are approximated by three-dimensional segmentation of experimental clinical images obtained from multispiral computer tomography (MSCT). The model adequately describes the possible configuration of swirling flow in the left ventricle and is a part of a comprehensive study of swirling flows in different compartments of heart, which comply with a family of the exact solutions of hydrodynamic Navier–Stokes equations for the class of quasipotential¹ swirling flows. Computer visualization shows how simulated by SPH method jet of a model liquid, which is placed in limited space, remains continuity and keeps its clockwise vorticity along the direction of the flow propagation during the whole cycle. Then it turns on approximately 120° by the time of ejection into the aorta. Such structure of the flow provides more effective pumping of blood as a model liquid through the ventricle as compared to a lamellar flow mode.

This article provides an overview of theoretical studies and clinical practice of using thoracic electrical bioimpedance (TEB). TEB is a noninvasive method for the measurement of cardiac output, cardiac index, systolic time intervals, and other hemodynamic parameters. The opinions of modern authors regarding the usage of this method are still controversial. However, many studies have proved that TEB is an accurate, reliable and promising method for monitoring the relative changes in hemodynamics in many clinical situations and in physiological studies of cardiac activity.