Fiziologiâ čeloveka

Gamma-band abnormalities are consistently reported in schizophrenia and attributed to disturbances of the excitation-inhibition balance in the brain. However, results in clinical high-risk groups are rare and quite inconsistent. The aim of the present study was to determine the characteristics of the resting-state gamma-band activity (range 30–45 Hz) in the clinical high-risk group (CHR, 110 patients) in comparison with schizophrenia patients (66 patients) and mentally healthy (62 subjects) male individuals. Correlation analysis with clinical characteristics were also conducted, and comparisons were made between patients who did or did not convert to psychosis during catamnestic follow-up. Correlations of gamma-band spectral power with gamma-aminobutyric acid (GABA) concentration and glutamine+glutamate index (GLX in frontal lobes were also analyzed. Statistically significant differences in gamma-band spectral power were revealed only between the CHR group and schizophrenia patients. In CHR patients GABA levels were decreased compared to healthy controls in the left frontal lobe, however there were no correlations between GABA and gamma-band spectral power. The results suggest some degree of “normality” or “compensation” of the processes of gamma-band activity generation (30–40 Hz) at clinical high risk of schizophrenia.

The concept of clinical-high risk (CHR) for schizophrenia implies the possibility of identifying a potential predisposition to future schizophrenia manifestation. An important goal of biological psychiatry is conducting research aimed at understanding the neurophysiological mechanisms of this condition. In this study, saccade characteristics of patients at CHR for schizophrenia (n = 15) and healthy participants (n = 15), as well as parameters of their slow negative potentials in the one-second interval preceding the signal to perform a saccade in a “memory-guided saccades/antisaccades” paradigm were analyzed. 12 participants from the CHR group also underwent magnetic resonance imaging (MRI) for subsequent comparison with the control group selected from the laboratory database. Saccade latencies and error rates were higher in the CHR group. There were also found lateral differences in CHR, but not in the control group. However, no between-group differences were observed in studied electrophysiological and MRI parameters. The obtained results may be interpreted as indirect signs of impairments in executive control, interhemispheric asymmetry and connectivity in the CHR group, although further studies are required to determine the possibility of using slow negative potentials parameters as clinical markers.

Motion of the common center of pressure (CCP) and center of pressure (CP) of each leg was studied in subject standing by each leg on separate force platform. Subject maintained the vertical posture during ordinary standing and during standing with visual feedback from the CCP position presented on the monitor. In both conditions the body weight was either symmetrically distributed between legs or partially transferred to right or to left leg. During standing with symmetrical loading of both legs the visual feedback led to the decrease the standard deviation of CCP and CP of each leg. After the transfer of the body weight on one leg standard deviation of the CCP and CP of each leg was not changed when the visual feedback was present. It is likely that the afferentation from loaded leg was sufficient for define the equilibrium body position. The velocity of motion of CCP increased with presence of the visual feedback during standing with all variants of weight distribution. The velocity of motion of CP of left leg increased with visual feedback during standing with symmetrical load and with load of the right leg. The velocity of motion of CP of right leg increased with visual feedback during standing load of the left leg. One could suggest that the tracking of the CCP position was mainly occurred by the leg that less involved into postural control. During standing with symmetrical weight distribution the afferentation from dominant leg more significant for the elaboration of referent body position for maintaining of vertical posture and the tracking CCP position influenced greater on the motion of the CP of the nondominant left leg. During standing with asymmetrical weight distribution the loaded leg is more involved into postural control and the tracking CCP position occurred by unloaded leg. It is suggested that the elaboration of referent body position for maintaining of vertical posture require the stationary position for leg that was mainly involved into postural control.

The aim of this work was a synchronous study of cardiovascular and respiratory indicators with a search for their relationship among residents of different latitudes and in high-latitude Arctic expeditions. The effect of place of residence on cardiorespiratory system parameters was studied in 113 men – workers of industrial enterprises (Sochi, Moscow, North). Adaptation to short-term Arctic expeditions was assessed in men (43 people in total, aged 35–60 years); 15 Moscow residents of the same age served as a control. The dynamics of adaptive processes in Arctic expeditions was assessed based on the results of testing before and after the start of the expeditions, on SP-41 – monthly. Two two-minute recordings were made on the spiroarterioacardiorrhythmograph (SACR) device: with voluntary breathing and with controlled breathing at a frequency of 6 cycles per minute. The amplitude-temporal values of the average respiratory cycle were assessed, as well as the statistical parameters of heart rate variability (HRV) SDNN and RMSSD. It has been shown that residents of the North, in contrast to both southerners and Muscovites, are characterized by a shorter inspiration. In the HRV indices, northerners showed lower SDNN values compared to Sochi residents, with a similar trend (p = 0.065) for the RMSSD value. Only northerners had correlations between the respiratory and HRV indices. We did not detect any dynamics of the assessed indices of the cardiorespiratory system in short-term (up to 4 weeks) Arctic expeditions, neither with any of the breathing patterns used, nor with double or triple testing. In monitoring at SP-41, it was found that 2–3 days after the start of the expedition, under controlled breathing conditions, the RMSSD index was reduced. A month after the start of wintering, a decrease in the tidal volume in the controlled breathing test (at the trend level, p = 0.078) and a decrease in the SDNN and RMSSD indices were recorded. In high-latitude expeditions, a decrease in autonomic regulation indicators is observed against the background of a reduction in volumetric, but not time-related indicators of the respiratory cycle, which is revealed only when breathing at a frequency of 6 cycles per minute.

A model of contrast sensitivity of the human visual system when perceiving sinusoidal gratings moving at angular speeds of up to 1000 degrees per second is considered. The model is built on the basis of a tremor modulation signal, which is taken to be the difference in the concentration of the photoreagent at the extreme points of the tremor, normalized to the level of adaptation. The model details the dependence of contrast sensitivity on physiological factors such as photoreceptor size, amplitude and frequency of tremor for adaptation brightness of 0.001–1000 cd/m². The model establishes a relationship between the results of measuring the contrast sensitivity of the visual system and the results of measuring natural tremor oscillations of the eyes during the perception of stationary and dynamic stimuli.

The review summarizes modern concepts about iron metabolism in the human body under terrestrial conditions and during space flights. The processes of absorption, transport, deposition and excretion of iron from the body, the effect of regulatory proteins, transporter proteins and receptor proteins on the metabolism of this trace element are considered. Special attention is paid to iron metabolism among participants in ground-based model experiments simulating the effects of space flight factors, as well as among crew members of expeditions to the Mir space station and the International Space Station. The paper presents and analyzes, from a modern point of view, experimental data on the peculiarities of iron metabolism in humans under extreme conditions of vital activity.