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In our work, we compare EEG time-frequency features for two types of K-complexes detected in volunteers performing the monotonous psychomotor test with their eyes closed. Type I K-complexes preceded spontaneous awakenings, while after type II K-complexes, subjects continued to sleep at least for 10 s after. The total number of K-complexes in the group of 18 volunteers was 646, of which of which type I K-complexes was 150 and type II K-complexes was 496. Time-frequency analysis was performed using continuous wavelet transform. EEG wavelet spectral power was averaged upon several brain zones for each of the classical frequency ranges (slow wave, δ, θ, α, β 1 , β 2 , γ bands). The low-frequency oscillatory activity ( δ-band) preceding type I K-complexes was asymmetrical and most prominent in the left hemisphere. Statistically significant differences were obtained by averaging over the left and right hemispheres, as well as projections of the motor area of the brain, p<0.05. The maximal differences between the types I and II of K-complexes were demonstrated in δ-, θ-bands in the occipital and posterior temporal regions. The high amplitude of the motor cortex projection response in β 2 -band, [20;30] Hz, related to the sensory-motor modality of task in monotonous psychomotor test. The δ-oscillatory activity preceding type I K-complexes was asymmetrical and most prominent in the left hemisphere may be due to the important role of the left hemisphere in spontaneous awakening from sleep during monotonous work, which is an interesting issue for future research.

Objective: To assess the objectivity of measuring the level of sleepiness in the subjects using a monotonous psychomotor bimanual tapping test developed by us, performed on mobile devices running Android OS., Material and Methods: Four hundred and ninety-four hour-long experiments with the performance of a psychomotor test were conducted on 102 students. Using the method of mixed linear models, correlations between the levels of sleepiness according to the Karolinska Sleepiness Scale (KSS) and the Epworth Sleepiness Scale (ESS) and the behavioral indicators of the test were evaluated., Results: Statistically significant correlations between the increase in KSS scores and such indicators as a decrease in the total number of button taps and an increase in the frequency of «microsleep» episodes are shown. Statistically significant correlations of ESS score characteristics with the behavioral indicators of the test were not found., Conclusion: A large statistical material shows a reliable correlation of the parameters of the psychomotor test with the level of sleepiness on the Karolinska scale, which allows using the mobile application developed by us to determine the current level of sleepiness /alertness in the field.

Objective: To study interhemispheric asymmetry (IHA) according to electroencephalography (EEG) data of a healthy person during cognitive awakening from the second stage of daytime sleep before restoring the performance of the psychomotor test., Material and Methods: In 23 healthy adult subjects, we studied IHA in the amplitude-amplitude interaction of EEG rhythms for 20 sec segments before spontaneous awakening determined by the moment the alpha-rhythm appearance on the EEG and the subsequent onset of psychomotor activity. The state of the subject during this period (in the initial stage of the so-called cognitive awakening preceding the behavioral awakening), when the person is unable to move, but is able to perceive external stimuli, is an experimental model for highlighting signs of conscious activity of patients when coming out of a coma. Wavelet transform was used to calculate the rhythmic characteristics of bioelectrical activity. The Kendall correlation coefficient served as a measure of rhythm interaction., Results: IHA in the interaction of EEG rhythms is dynamic nature and formed by theta rhythm connections with alpha2- and beta-rhythms in the left brain hemisphere and delta-type connections in the right., Conclusion: Possibly, the greater activation of the left hemisphere is related to the retrieval of an instruction from memory, which subsequently allows to return to the activity interrupted by sleep.

Objective: To test the hypothesis that weak electromagnetic fields of low frequencies (0.5-26 Hz) could affect daytime sleep features and structure., Material and Methods: Parameters of daytime sleep continuity were compared in the study with counterbalanced control/exposition (40 min exposure to electromagnetic field at 1 Hz/0.004 μT) scheme in 22 healthy volunteers. Nonlinear regression model was used to assess daytime sleep continuity., Results: Exposure to a weak electromagnetic field of ultra-low frequency significantly improved the quality of sleep, assessed by the indicator of sleep continuity, namely, there were fewer transitions from the second and deeper stages of sleep to the first stage and to the state of wakefulness ( p <0.0001)., Conclusion: The results can be used to develop non-pharmacological methods of sleep correction, as well as to improve the quality of short-term sleep and its positive effect on well-being, cognitive function and working capacity.

A psychomotor test for induction of the state of monotony and visuomotor coordination analysis has been developed. The subject had to follow a small cicle slowly moving in circular orbit on a screen with a "mouse" cursor. When an additional target unexpectedly appeared, he had to catch it with a cursor and click a "mouse" button when the cursor was on it. Eye movements were recorded with an eyetracker. The experts marked the episodes of declined vigilance based on EEG and video of a subject. Analysis of parameters of visuomotor coordination demonstrated their high sensitivity to the vigilance decline. We have found the increase of variability in pursuit eye movements and "mouse" cursor movements during the episodes of lowered vigilance before the appearance of the additional target and also a growing latency of saccadic eye movements, cursor movements and "mouse" button presses when the cursor contacted the additional target. For latency of saccadic eye movements, cursor movements and mouse button presses significant increase was found 2-3 min before experts can detect vigilance decline too. The ability by visuomotor coordination parameters to predict the moments of critical vigilance decline is discussed.

We tested our earlier suggested hypothesis that one of mechanisms for failures of performance of behavioural tasks during microsleep is a spontaneous generation of ponto-geniculo-occipital (PGO) waves that suppress transmission of visual information from the retina via lateral geniculate nucleus to primary visual cortical areas and the striatum, and therefore significantly impair visual perception and attention. Experiments were done during the nighttime. Monotonic testing during performance of the two-alternative psychomotor test invoked participants into a state defined as a microsleep with open eyes. For each participant we made a comparative analysis of intensity of EEG spectrum during state of microsleep with open eyes when failure in test performance occurred and during accurate performance in waking state. Following trends in changes of EEG spectrum were found: increase in intensity of low alpha-range, and decrease in intensity of high alpha- and beta-ranges. Changes in theta-, low beta- and gamma-ranges were differently directed. Taking into account the known from the literature data these changes specify decrease in activation of primary visual cortical areas. Revealed data could support our hypothesis concerning mechanism of visual-motor disturbances during microsleep with open eyes.

Visual-motor coordination is necessary for successful performance of everyday activities. Many tasks, such as driving or operating devices in the workplace, require a variety of coordination patterns with different levels of compatibility between the eyes and the hand. The psychomotor test was developed which makes it possible to analyze visual-motor coordination disorders caused by a decrease in the level of wakefulness. A small circular target (14 mm in diameter) was moving with a low constant velosity (12 mm/s) in a circular trajectory (80 mm in diameter) with a period of 20 s. Subjects were instructed to keep the mouse-driven cursor inside a target, overstepping the limits of the moving target was considered as an error. To test the attention level, an additional stimulus was introduced which appeared for 3 seconds with an interval of 15 to 40 s. When the stimulus appeared, it was required to touch it with the cursor and click the mouse button. Cursor trajectories have a temporal resolution of 120 Hz. Eye movements were recorded with a PC-based Eyegaze Development System (LC Technologies, USA) measuring corneal reflectance with a collection rate of 120 Hz. Monotonous character of the test performance induced drowsiness and led to errors 25-30 minutes after the beginning of the experiment. Changes in physiological vigilance level was evaluated with EEG recording. Analysis of the dynamic characteristics of smooth and saccadic eye movements and hand movements showed their high sensitivity to a decrease in efficiency of operator's activity caused by a drop in the level of wakefulness. It is suggested that further development of this approach to measuring eye-hand coordination will promote working out a contactless method for the express diagnostics of the critical levels of drowsiness as well as for the definition of professional characteristics of an operator.

The proposed modification of boundary element method (BEM) makes it possible to solve direct EEG problem taking into account individual head geometry. This modification decreases computational cost thus enabling practical usage of BEM for localization of EEG dipole sources. The method developed was applied for error estimation of dipole localization using spherical approximation with the aid of BESA software. It was shown that the localization error of BESA for real head geometry could reach 2 cm.