Influence of neuroendocrine shifts in the pubertal period on the working memory operation in adolescents

It was found that the volume of working memory in adolescents at the initial pubertal stages (II–III) was lower than in adults. Analysis of the event-related potentials (ERPs) in various cortical areas in adolescents when they compared two successive pictures revealed specific features of neurophysiological mechanisms of visual working memory at the early pubertal stages. As compared to adult subjects, the adolescents were characterized by longer latencies and higher amplitudes of the early components of the ERPs. Certain differences were revealed in the functional organization of working memory both at the stages of stimulus fixation and in its comparison with the current information.     

Changes in nonlinear characteristics of heart rate variability under functional load on the cardiovascular system in healthy subjects and coronary heart disease patients

Some nonlinear characteristics of heart rate variability in the course of functional tests with physical exercise are described. Two groups of volunteers participated in the tests: a control group of 32 healthy subjects (group 1) and a group of 35 coronary heart disease (CHD) patients (group 2). Two series of experiments were performed for each group. An active orthostatic test (AOT) was used in the first series, and a gradually growing physical load on a bicycle ergometer (bicycle ergometer test, BET), in the second series. Along with statistical indices of heart rate (the mean RR interval and standard deviation), nonlinear indices of heart rate were estimated: the correlation dimensionality (D ₂) and approximate entropy (ApEn). Trends of the changes in nonlinear indices of heart rate have been found. The D ₂ and ApEn decreased in both groups of subjects during the AOT and BET under the maximum load. However, the groups of healthy subjects and CHD patients differed in the reactivity of indices, the amplitude of changes in nonlinear indices being narrower in the latter group than in group 1. Differently directed shifts in standard deviation (SDNN) and nonlinear indices have been found. Thus, the data obtained with the use of nonlinear heart rate characteristics show that heart rate under physical load is more multivariate and diverse in healthy subjects at rest and the amplitude of changes during the AOT and BET is greater than in CHD patients, which is a result of the specific autonomic control of heart activity in cardiovascular pathologies.     

Characteristics of the formation of compensatory and adaptive responses of sailors to chronic stress

Rhythmography and omegametry have been used to study the physiological functions in 45 sailors during a 157-day sea voyage in the northern and northwestern Atlantic. The characteristics of the formation of compensatory and adaptive responses of sailors to long-term, chronic stress caused by work at sea are analyzed. Patterns of the variation in autonomic tone in different months of the long voyage and the dependence of the constant potential of the brain on the autonomic balance are described. Markov chain models are used to simulate the adaptation outcome for different states of the autonomic balance. The specific features of the functional physiological characteristics of sailors at different levels of functional reactivity are analyzed. It is found that humoral mechanisms serve as a link between the factors ensuring structural and functional rearrangement of the mechanisms of constant potential formation in chronic fatigue. A reciprocal mechanism is shown to underlie the formation of functional states during the second half of the voyage.     

Psychophysiological indices in six-to eight-year-old children under information load depending on anxiety as a stable individual characteristic

The study of psychophysiological indices in children aged six to eight years under information loads of various complexity showed that anxious subjects were characterized by a high level of nonspecific activation at rest and a shift of the autonomic balance towards a relative domination of the tone of the sympathetic division of the autonomic nervous system (ANS). The information load in the “auto-rate” mode caused in children aged six to eight years an increase in the level of nonspecific activation and the activity of sympathetic regulation and an inhibition of parasympathetic regulation. An information load in the “maximum rate of work” mode caused a decrease in the quantitative and qualitative indices of mental activity in comparison with that under comfortable conditions and a subsequent increase in autonomic shifts and the level of situational anxiety. The decrease in the efficiency of intellectual work performed at a maximum rate against the background of a high level of nonspecific activation and an increase in situational anxiety in both groups apparently reflected an increase in the activity of the modulating cerebral system due to the domination of the nonproductive activation system related to defensive behavior. At the same time, in children with a high personal anxiety, autonomic manifestations of activation and situational anxiety in both modes of work were more distinct and the efficiency of work lower than in subjects with a low anxiety. This indicates that, in anxious children, due to the excess activation of the sympathetic division of the ANS, the information load has a higher physiological cost. Thus, children with a high level of personal anxiety under intense information loads are characterized by a larger increase in the activity of the sympathetic division of the ANS and the attenuation of the effect of the parasympathetic division; a considerable increase in situational anxiety; low efficiency of activity; and, hence, its high physiological cost.     

Measuring the distribution of plantar pressures during walking in patients with multiple sclerosis to evaluate treatment efficiency

The relationship between the parameters of the distribution of plantar pressure and the state of a patient with multiple sclerosis has been studied with repeated measurements, before and after (or during) treatment. The possibility of using this method for study of walking function impairment in a chronic demyelinating process is considered.     

Plasticity of cortical structures under the conditions of neurological deficit accompanied by a disorder of hand movement: Modern approaches to rehabilitation

Reorganization of cortical structures under the conditions of neurological deficit is an important interdisciplinary problem. This problem closely unites neurologists, physiologists, and mathematicians, which makes it possible to develop rehabilitation measures taking into account individual features. Fine hand movements under the conditions of motor pathology are an ideal model for investigation of neuroplasticity.     

EEG θ rhythm in preterm and full-term infants at the age of five months in endogenous attention

EEG indicators of endogenous attention (EnA) were studied in healthy infants carried to term and extremely preterm infants at a corrected age of five months. The cortical topography of the spectral amplitudes of the EEG θ rhythm was studied during long-term attention of the children to a new visual stimulus (exogenous attention, ExA) and during the retention of anticipatory attention under the conditions of constant appearance and disappearance of a stimulus in the paradigm of visual expectation (EnA). The relationship between reactive changes in the EEG θ rhythm during the retention of EnA and the behavioral parameters of the infant’s ability to retain this type of attention was also assessed. In five-month-old infants, the retention of EnA, in contrast to simpler types of attention to an exogenous stimulus, was accompanied by the appearance of a highly synchronized EEG θ rhythm (3.6–5.2 Hz) with a topical amplitude maximum in the lower temporal associative areas of the cortex. The ability to maintain EnA in children of this age is directly related to the reactive increase in the θ rhythm in the lower temporal areas of the cortex during the retention of EnA as compared to ExA. The deficit of EnA control in healthy extremely preterm (HEP) infants was associated with a relative deficit of the functional synchronization of the θ rhythm in the lower temporal areas of the cortex during the retention of EnA compared to full-term infants. In HEP infants, a decreased synchronization of the θ rhythm was equally typical of EnA and ExA. However, its cortical location depended on the type of attention. The functional nature of the θ rhythm inhibition in HEP infants suggests that this abnormality was related to alterations in the neurotransmitter interactions between the limbic and cortical structures, rather than to structural defects. These alterations could be one of the causes of the partial deficit of EnA in HEP infants.     

Correlation between electrophoretic mobility and extent of aggregation of human red blood cells

The extent of aggregation, electrophoretic mobility, and zeta potential of human erythrocytes were measured in the presence of some hormones and prostaglandins. Catecholamines, adrenomimetics, and prostaglandins were found to significantly increase the extent of aggregation; the electrophysiological characteristics of the cells were affected in different ways.     

Patellar reflex: I. Studies in healthy subjects

The reflex activity of the flexors and extensors of the knee joint in response to a tap with a percussion hammer at a patellar tendon has been studied in healthy subjects. The studies were performed while the subjects were in a relaxed state at rest or during reinforcement using Jendrassik’s method. The contribution of muscle receptors to the reflex is discussed. It has been demonstrated that the initial burst of activity in the flexors is a “hum” of potentials generated by the quadriceps muscle of the thigh.