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Evoked EEG theta and alpha rhythm synchronization/desynchronization responses to facial stimuli were studied in healthy subjects (n = 35) in an experiment involving formation of a set to an emotionally negative facial expression. The magnitude of the evoked theta activity synchronization response in the group of subjects with the plastic type of set was greater and the latent period was shorter than in the group with the rigid type of set. These differences were particularly clear in the temporal and parietal-occipital areas. A sufficiently high level of the phasic theta potentials synchronization response, reflecting the level of activity of the corticohippocampal feedback system during the perception of facial stimuli, was required for rapid substitution of the set to facial expressions. In subjects with plastic sets, the evoked low-frequency alpha potentials response was apparent as synchronization, while that in subjects of the "rigid" group consisted of desynchronization. These results were interpreted in terms of the concept of Klimesch (2007) that the evoked alpha potentials synchronization response is a measure of inhibition in cognitive activity. The alpha potentials synchronization response reflects the process of inhibitory control, which plays an important coordinating role in organizing the plastic properties of the set in relation to its inhibition when it ceases to correspond to new stimuli. The involvement of the tonic and phasic forms of cortical activation, mediated by the corticohippocampal and frontothalamic brain systems, in the functional organization of the cognitive set to an emotionally negative facial expression is discussed.

Coherence functions in cortical electrical potentials in the theta (4-7 Hz) and alpha ranges (8-13 Hz) recorded during the formation and testing stages of a visual set to facial images bearing an emotional expression (an angry face) were studied in healthy adult subjects (n = 35). Differences in the spatial synchronization between theta and alpha potentials were seen, especially in rigid forms of the set, in which cases of erroneous perception of facial expressions were seen with contrast and assimilative illusions. This group of subjects (n = 23) showed increases in theta potentials between the dorsolateral areas of the frontal cortex (the orbitofrontal cortex) and the temporal area in the right hemisphere. A mechanism is proposed for the development of visual illusions. Analysis of the coherence functions of cortical potentials in the theta and alpha ranges generates a "window" which can be used to study the operation of the two functional systems integrating brain activity, i.e., the corticohippocampal and frontothalamic, in the perception of a facial expression. The frontothalamic system is associated with more diffuse types of cortical activation, especially in its anterior areas. The theta rhythm system evidently facilitates integration of the frontal cortex with the temporal area in the right hemisphere and the connections of the latter with the parietal and central zones in both hemispheres.

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.

Parameters of the formation of a visual nonverbal set and the rate of its replacement with a new set were compared in children of three age groups: 5-6, 6-7, and 9-10 years. The vast majority of subjects (27 of 30 preschool children and 42 of 43 third-grade children) showed clear set effects. Age-related differences in set plasticity and the dynamics of reaction times to test stimuli were observed. The set was more rigid in children aged 5-6 years than in older children. Differences in the dynamics of the spatial organization of alpha and theta activity were seen in the anterior areas of the cortex at different stages of the set in children of different age groups. Analysis of cortical potentials coherence functions and behavioral parameters led to the hypothesis that the frontothalamic selective attention system and the corticohippocampal connection system responsible for the cortical processing of new visual information and episodic memory function are involved in organizing the visual set. A critical age (from six to seven years) was identified in the formation of plastic types of visual nonverbal sets.

The coherence functions of cortical electrical potentials were studied in 35 healthy adults in the alpha (8-13 Hz) and beta (14-25 Hz) ranges, recorded at the stages of formation and testing of a visual set to images of faces bearing different emotional expressions. At the set actualization stage, the frontal area showed significant increases in intra-and interhemisphere coherence of potentials in the alpha range and coherence of potentials between the frontal and temporal areas of the cortex in the right hemisphere. These analytical results support the suggestion that the formation and actualization of a set to emotional facial expression are predominantly associated with activity in the frontal areas of the cortex. This conclusion is based on the view that the extent of spatial synchronization of electrical potentials is a measure of the functional relationships between corresponding cortical areas and their cooperativity, and thus reflects the state of their activity.

Experimental data from healthy humans on the context dependence of cognitive activity involved in the process of substituting a previously formed unconscious set with a new set appropriate to the altered conditions are discussed. The mobility/rigidity property of the visual set changes depending on the nature of the additional task introduced into the context (stimulus recognition or identification of the spatial position of a stimulus). It is hypothesized that the process of set substitution is facilitated when the context of cognitive activity includes alternation of the involvement of the ventral and dorsal visual systems in information processing.

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.

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.

The regulatory function of set in cognitive activity and the organization of human behavior is discussed. The effect of set is identified by means of the recording of the N150 and P300 components of evoked cortical potentials in response to sounds of varied significance (the oddball paradigm); this offers the possibility of shifting from a phenomenological description of this phenomenon to a study of its neurophysiological basis.

The role of unrecognized forms of reinforcement in the function of the discrimination of microintervals of time was investigated in emotionally excitable adults. The word "good" [""khorosho""] (positive reinforcement) and a word associated with the subject's negative emotions (negative reinforcement) were utilized as feedback stimuli. Experimental confirmation was obtained of the hypothesis that unrecognized phenomena of the external milieu can exert an influence on conscious mental activity and on the learning process in man. Unrecognized semantic stimuli can fulfill the function of a reinforcing factor, and thus participate in the process of learning a cognitive activity accomplished at the conscious level.

The P300 component of the evoked potential was recorded over both hemispheres in order to study interhemispheric differences in the process of perception of subliminal verbal stimuli. The stimuli--subliminal words, neutral and emotional--were presented at random to the left or right visual fields. In response to an unrecognized emotional word, the amplitude of P300 wave increased diffusely over both hemispheres as compared to that to a neutral word, with no changes in interhemispheric differences. The interhemispheric difference changed considerably in the presence of an 'unaccountable' emotion caused by a subliminal word. This suggests a unilateral activation of the right hemisphere and a predominant role of this hemisphere in the cortical organization of the unconscious function 'unaccountable' emotion.