[Interhemispheric asymmetry of EEG rhythm connections during spontaneous awakenings after short sleep episodes during a monotonous psychomotor test]. / Mezhpolusharnaya asimmetriya svyazei ritmov EEG pri spontannykh probuzhdeniyakh posle kratkovremennykh epizodov sna pri vypolnenii monotonnogo psikhomotornogo testa.

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.

[The effect of music containing binaural beats on daytime fall-asleep dynamics]. / Vliianie muzyki, soderzhashchei binaural'nye bieniia, na dinamiku dnevnogo zasypaniia.

AIM: To test the hypothesis that listening to the music with the effect of binaural beats of theta and delta range during nap decreases sleep latency defined by 2nd slow wave sleep stage appearance, as well as improves its stability. MATERIAL AND METHODS: The experimental set of 20 min duration was established according to the counterbalanced scheme with 21 subjects. Each subject participated in two attempts: one attempt included sound stimulation (music) and another one was sham (silence). RESULTS AND CONCLUSION: The decrease in sleep latency during stimulation is not confirmed reliably. The increase in sleep stability has been confirmed reliably using nonlinear regression model. The findings can be used in the development of non-pharmacologic ways of sleep treatment.

[Relationships between the Flexibility of Cognitive Performance and the Response of Alpha-Rhythm in the Go/NoGo Task].

During the experiments, healthy subjects (n = 35) completed Go/NoGo task with a set towards the recognition of negative face expression; the visual stimuli were set in the middle of a 16-second-long interval between target (face) and triggering stimuli. The local changes in low-frequency alpha-oscillations in response to stimuli (desynchronization after a positive Go stimulus and synchronization after an inhibitory NoGo stimulus) take place in posterior frontal and anterior temporal lobes of the left hemisphere, i.e., in cortical areas directly involved in speech processes. In subjects with flexible set towards recognition, we observed synchronization of alpha-rhythm after inhibitory NoGo stimulus; in subjects with more stable set, this did not occur. Thus, we obtained new experimental data confirming that induced synchronization of alpha-oscillations reflects the enhancement of descending inhibitory control of the prefrontal cortex.

[Influence Additional Cognitive Tasks on EEG Beta Rhythm Parameters during Forming and Testing Set to Perception of the Facial Expression].

The research of changes of a beta rhythm parameters on condition of working memory loading by extension of a interstimuli interval between the target and triggering stimuli to 16 sec is investigated on 70 healthy adults in two series of experiments with set to a facial expression. In the second series at the middle of this interval for strengthening of the load was entered the additional cognitive task in the form of conditioning stimuli like Go/NoGo--circles of blue or green color. Data analysis of the research was carried out by means of continuous wavelet-transformation on the basis of "mather" complex Morlet-wavelet in the range of 1-35 Hz. Beta rhythm power was characterized by the mean level, maxima of wavelet-transformation coefficient (WLC) and latent periods of maxima. Introduction of additional cognitive task to pause between the target and triggering stimuli led to essential increase in absolute values of the mean level of beta rhythm WLC and relative sizes of maxima of beta rhythm WLC. In the series of experiments without conditioning stimulus subjects with large number of mistakes (from 6 to 40), i.e. rigid set, in comparison with subjects with small number of mistakes (to 5), i.e. plastic set, at the forming stage were characterized by higher values of the mean level of beta rhythm WLC. Introduction of the conditioning stimuli led to smoothing of intergroup distinctions throughout the experiment.

Relationship between the plasticity of a set to an emotional facial expression and the load on working memory.

The effects of increasing the loading on working memory (by introduction of an additional cognitive task into the experimental context) on the recognition of an emotional facial expression using a visual set model were studied in healthy adult humans. A relationship was found between the plasticity of the cognitive set to an emotional facial expression and working memory: increases in the load on memory slowed set substitution when the situation changed. The set became more rigid, as indicated by an increase in the number of trials showing erroneous assessments of facial expressions, i.e., contrast and assimilative illusions, at the test stage of the experiment. The role of internal states in the increase in the number of erroneous assessments of emotional facial expressions when working memory was loaded is discussed.

The role of the cognitive activity context in the conservatism of unconscious visual sets.

Studies in healthy adults were performed to compare measures of the rigidity of a verbal set in three series of experiments: in series 1, pseudowords were presented at the set-forming stage of the experiment, while common words were presented in the test stage; series 2 used the pseudoword/word conditions of series 1 with the additional task of identifying the position of a target stimulus in a matrix, requiring discrimination from other symbols in terms of two characteristics; in series 3, the pseudoword/word test was followed by an initial task consisting of identifying the matrix position of a target stimulus in conditions in which the need to discriminate was minimized. The results supported the hypothesis that the rigidity of a visual set depends on the cognitive activity context. This property is significantly dependent on the loading applied to working memory and the cognitive tasks solved by the subject, particularly the ratio of involvement of the ventral and dorsal visual systems in the cortical processing of sequentially acting verbal and non-verbal visual stimuli. The cognitive set paradigm serves as a model for experimental studies of the roles of the ventral and dorsal visual systems in organizing recognition functions.

Dependence of the cognitive set on the involvement of the ventral and dorsal visual systems in cognitive activity.

Measures of the stability of a non-verbal visual set were compared in healthy human subjects in three series of experiments: 1) controls, in which a pair of set-forming stimuli (images of circles) were presented; 2) in the context of a test with a non-verbal set, subjects were presented with an additional task consisting of recognition of pseudowords (words); and 3) as before, but the additional task consisted of identifying the position of a target stimulus in a matrix of letters. There was a significant decrease in the stability (rigidity) of the non-verbal set on introduction of the additional task consisting of identifying the spatial position of a target stimulus; conversely, there was an increase in rigidity when the task consisted of recognizing the quality of a stimulus. Coherence analysis of cortical potentials in the alpha range showed that changes in the spatial organization of cortical electrical activity were significantly different, depending on the nature of the additional task: when the additional task involved recognition of a verbal stimulus, coherence connections were strengthened in the frontal-temporal-parietal areas of the right hemisphere; presentation in the context of a visuospatial task resulted in greater changes being observed in the anterior areas of the right hemisphere. It is suggested that the successful performance of mental functions requiring relatively rapid shifts in unconscious sets on changes in situation occurs in conditions of alternation of different types of cognitive tasks when cortical processing of visual information is mediated predominantly by one of the visual systems - either the ventral ("what?") or the dorsal ("where?") and, correspondingly, with the involvement of the anterior and posterior cortical selective attention systems.