Volume 45, Nº 5 (2019)

Age-related trends in the strength of functional and effective connectivity between key cortical structures that belong to the three most important resting-state neural networks: the default mode network (DMN), the key event detection network (salience network, SN) and the central executive network (CEN) were investigated in adolescents of both sexes. The study involved 34 adolescents of the younger age group: 11–13 years old (12.61 ± 0.75 years, 13 girls and 21 boys) and 54 adolescents of the older group: 14–16 years old (15.00 ± 0.75 years, 20 girls and 34 boys). Frequency-specific estimates of the strength of functional and effective connectivity between the nodes of DMN, SN and CEN were computed in six frequency bands θ (4–7 Hz), α₁ (7.5–9.5 Hz), α₂ (10–13 Hz), β₁ (14–18 Hz), β₂ (20–27 Hz) and γ (30–40 Hz) using the vector autoregressive modeling of cortical sources of EEG registered in the resting condition. The analysis of functional connectivity revealed age differences in the θ frequency range, in which the strength of connections between the nodes of all networks in the younger age group was higher than in the older group. Besides, sex-related differences were found in the beta-2 and gamma ranges: the connections between the nodes of DMN were stronger for girls than for boys. The analysis of effective connectivity (directed influences) revealed a significant effect of age in all frequency ranges for the CEN and DMN resting-state networks; for SN, this effect was significant in all but the beta-2 and gamma ranges. The most pronounced age-related changes were found for bottom-up connections directed from more caudal to more frontal areas in CEN and DMN, and in the younger age group, the strength of effective connections was greater than in the older one. The effect of sex on the strength of effective connections was limited mainly to the younger group and manifested itself in stronger DMN and CEN connectivity in girls (as compared with boys) .

We have analyzed EEG alterations during a passive hand movement test in ten patients with varying degrees of hemiparesis caused by brain injury and compared them with normal data (17 healthy volunteers). The fMRI responses of the patients were normal. It was found that additional brain structures (that seem to be untypical of healthy people) are included in the reactive process in patients with brain injury. Additionally, we observed a widening of affected frequency bands. We observed the highest correlation with the degree of hemiparesis for the topographical parameters of changes in EEG coherence during the passive hand movement test with specific response features of the brain hemispheres contra- and ipsilateral to the movement. It is discussed whether there is any involvement of the tactile component in the passive motor EEG response. The data are considered in the context of the earlier hypothesis [1, 2] on the participation of the extrapyramidal system in the compensation of a post-traumatic motor defect.

The study of clinical, psychopathological and neurobiological characteristics of affective-delusional states is important for clarifying the diagnosis and individual prognosis of disease development. Quantitative EEG allows us to assess objectively the brain functional state of such patients and to clarify the neurophysiological mechanisms underlying the characteristics of syndrome structure of mental disorders. The aim of the study was to search for baseline amplitude–frequency and spatial characteristics of EEG as possible indicators for prediction of therapeutic response in patients with manic–paraphrenic and manic–delusional states in the framework of endogenous mental disorders with different syndrome structure. The study was conducted in 73 women aged 18–55 years with affective–delusional disorders meeting the criteria of diagnosis codes F25.0 and F25.2 according to ICD-10 and differing in the syndrome structure: with a predominance of sensual-delusional (28 patients) or ideational–delusional (31 patients) disorders, as well as a group with manic–delusional states (14 patients). The quantitative assessment of patient’s mental state in the dynamics of therapy was carried out by the YMRS and PANSS clinical scales. The brain functional state was assessed using multichannel recording and spectral analysis of resting EEG. The correlation analysis revealed the relationships between individual quantitative clinical estimates after a course of therapy and EEG parameters recorded prior to therapy (potential predictors of therapeutic response). The intergroup peculiarities of the structure of correlations between the baseline (recorded before the therapy) individual EEG spectral power values and the quantitative YMRS and PANSS clinical estimates after the therapy were revealed in three syndromally different groups of patients. These EEG parameters can be considered as candidates for the role of predictors of individual therapeutic response in patients with manic–delusional and manic–paraphrenic states. They reflect either the initially reduced brain functional state, in particular, the frontotemporal cortical areas, or its initial hyperactivation, i.e., disturbance of the normal ratio of excitation and inhibition processes. Thus, variations in the ratio of excitation and inhibition processes, reflected in the baseline resting EEG parameters, apparently determine both the clinical manifestations of manic–paraphrenic and manic–delusional conditions and the brain adaptive resources in terms of the capacity and magnitude of patient’s individual therapeutic response.

We studied whether adaptation can occur in healthy subjects under conditions of standing in a three-dimensional virtual visual environment (VVE), which was destabilized, e.g., by introducing the in-phase coupling only between the subject’s body oscillations and the position of visible virtual scene. For approximately 1.5 h, the subjects performed 35 tests lasting 40 s each, standing quietly on a stabilograph, which recorded the oscillations of their body. The interval for rest between the tests was 20–25 s; after every 5 tests, the subjects rested sitting for 4–5 min. The posture maintenance analysis was based on the assessment of the amplitude–frequency characteristics of two elementary variables: the trajectories of the projection of the center of gravity on the support surface (variable CoG) and the difference between the trajectories of the CoP and CoG (variable CoP–CoG). The variables were calculated basing on the trajectories of the center of pressure (CoP) in the anteroposterior and lateral directions. We found that the standing under the conditions of the same type of destabilization of visible visual environment at the end of the tests was significantly improved. The amplitude and frequency characteristics of variables CoG and CoP-CoG was close to those observed in an immobile visual environment. The vertical posture maintenance was improved through changes in both the amplitude and frequency characteristics of variables CoG and CoP–CoG. Thus, we found that multiple repetitions of tests under conditions of virtual visual environment with unstable visible visual environment, resulting in the destabilization of the vertical posture, allowed subjects to effectively adapt and improve the equilibrium characteristics of the body.

It is now an established fact that blood flow in the heart and the major vessels has normally a helical pattern. The structure of this flow is described by the exact solution of the nonstationary hydrodynamics equations for a class of self-organized tornado-like jets of viscous fluids. Our previous studies have shown that the geometry of the aortic channel corresponds to streamlines of this class throughout the cardiac cycle, which is supported by a special distribution of viscoelastic properties of the flow channel wall along the aorta. As a result of age-related pathological processes and/or their surgical correction, normal viscoelastic characteristics of vessel walls inevitably become impaired. A diversity of impairments in the structure of the cardiovascular system causes negative alterations in the normal geometrical configuration of biological flow channels. Thus, any pathological alterations in vessel channels are accompanied by deteriorations in the structural parameters of blood flow. However, a direct experimental study of all the diversity of vessel lesions is associated with considerable complications. Thus, no studies have been conducted so far to identify the regularities of alterations in the structural parameters of a swirling blood flow in different pathological conditions of the vessel channel. In this study, we have created a physical model of the flow channel of the aorta, which was based on the nonlinear distribution of transverse elasticity in the walls of the aorta along its length. Further, we created a computer simulation of the constructed model flow channel dynamics throughout the cardiac cycle in correspondence with the standard curve for blood pressure changes. The simulation results were interpreted within the semi-empirical theory of self-organized tornado-like jets of viscous fluids. This interpretation allowed us to formulate the time-dependent quantitative characteristics establishing functional relations between the structure of blood flow and the geometry of the flow channel of the aorta throughout the cardiac cycle.

Numerous studies have indicated a close relationship between lipid metabolism disorders and the inflammatory component of atherogenesis. Excess endotoxin (ET) in the general circulation can induce chronic inflammation, and its role in atherogenesis is difficult to overestimate. The involvement of lipopolysaccharide (LPS) in atherogenesis in humans has been studied without assessing the morphological changes in the structure of the vascular wall. It seemed therefore of importance to study the dynamics of the systemic endotoxinemia (SEE) parameters as probable markers of atherosclerosis in association with a progression of morphological changes in the arterial wall. A total of 104 volunteers were examined. The patients had lipid profile abnormalities without clinical manifestations of atherosclerosis, reported themselves to be healthy, and belonged to the moderate risk category (2–4%) on the SCORE scale. A Control group (n = 9) comparable the patients by sex and age. All subjects underwent a duplex scanning of extracranial brachiocephalic arteries (BCA) and a venous blood testing for lipid profile and SEE parameters, including ET, antibodies to the hydrophobic and hydrophilic part of the LPS molecule, and their concentration ratio. The patients were divided into three groups based on the structural changes detected in the arterial wall by ultrasound testing: no morphological change in the BCA (Normal), a thickening of the intima–media complex (TIM), and identified atherosclerotic plaque (ASP). Patients of the ASP group have a significantly higher ET concentration and a reduced activity of anti-ET immunity (AEI) as compared with the accepted reference values and values observed in the TIM group. ET level was not increased, but the AEI activity was reduced in the TIM group, as well as in the Control group. All SEE parameters were within their normal ranges in the Normal group. The main risk factors in assessing the risk for detecting atherosclerotic plaque of the BCA were an age over 55 years and a decrease in antibodies to the hydrophobic part of the LPS molecule below 163 c. u. o. d. Significant differences observed in SEE parameters between patient groups made it possible to assume that an increase in blood LPS concentration and a decrease in AEI activity are risk factors for atherosclerosis.

The functional organization of the brain systems underlying higher order human activity is one of the key issues of modern psychophysiology and neurophysiology. Despite the continuous development of new methods, the relationships between the activity of individual cells (and their groups) and the activity of large brain areas observed by means of functional tomography are not yet fully understood. In this paper, we propose a solution for this problem basing on the common patterns of the principles of functional brain activity at the micro- (cells) and macro- (brain areas) levels. We compared the previously identified principles of the dynamic organization of the multicellular neuronal activity of the human brain with the recent fMRI findings basing on the combined analysis of local characteristics of energy consumption by the brain structures and their distant interactions. As a result, we assumed that many brain systems are composed of a large number of hidden nodes. Those nodes are included in the systems in certain periods only. For a wide range of activities, the brain regions are systematically involved in the actively working brain systems as hidden nodes, i.e., without changing their energy consumption, which was observed at both micro- and macro-levels of functional brain activity. These findings reflect the new phenomenon of the “hidden nodes” of the brain systems.

Electrical stimulation of the spinal cord (ESSC) is a method enabling researchers to confirm the existence of the stepping movement generator in humans. Currently, the ESSC-based technologies of motor rehabilitation of patients immobilized after spinal cord injury are actively developing. The impact of the serotonergic system in the organization of movement is intensively studied both at the systemic and the molecular–cellular level in a large number of researches. The aim of this review was to analyze the current experimental data on the participation of serotonergic system in the locomotor activity control at the spinal level with a focus on the processes related to electrical stimulation of spinal locomotor networks. Special interest is given to the serotonin-based regulation of human motor activity. The data on the use of serotonin-modulating pharmacotherapy for increasing the efficacy of the ESSC method in locomotor rehabilitation are presented in the final part of the review.