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At healthy people (n = 35) on model of the cognitive set on an angry face is shown: introduction of positive and negative coordinated stimuli Go/NoGo in the inter-stimuli interval can change considerably the top-down positive and negative influences of prefrontal cortex on the cortical areas participating in a visual perception and by that to influence plasticity of the set. The cortical topography of the top-down influences in response to NoGo is determined by local changes of power of fluctuations of potentials in alpha rhythm range. Changes of spatial synchronization of alpha potentials occurs only in their low-frequency range, depending on the level of plasticity of the set. At its rigid forms coherent communications between prefrontal and other cortical zones it is obviously more expressed in the left hemisphere. Apparently at rigid forms of cognitive activity left-side cortical activation with more essential involvement of speech, semantic functions, plays the compensating role.

Using a cognitive set to emotional facial expression as a model, induced synchronization/desynchronization of the cortical theta- and alpha-activities were studied in adult healthy people under conditions of increased load on the working memory (additional task of the verbal stimuli recognition). A correlation was found between behavioral (increase in the set rigidity) and electrophysiological (decrease of the induced theta-rhythm synchronization) data. A hypothesis is suggested that the earlier revealed increase in the tonic prestimulus theta-activity and suppression of the poststimulus phasic activation of the cortico-hippocampal system are one of the mechanisms of the decrease in plasticity of the cognitive function of the emotional facial expression recognition under conditions of the increased load on the working memory. Reciprocal relations between two functional systems of the brain activity integration (cortico-hippocampal and fronto-thalamic) in the process of recognition of emotional facial expression are 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.

Visual set (by D.N.Uznadze) was studied in three groups of 8-year-old children: children with EEG-signs of immaturity of fronto-thalamic activation system; children with a deficit of non-specific activation from mesencephalic reticular formation; children with normal development of these systems (control group). Children with a deficit of non-specific activation split in two groups: one group was similar to the control group in set-forming, set-shifting and response time dynamics; another group haven't displayed a set actualization stage and had a considerably bigger response time during attention shifting. Children with immaturity of fronto-thalamic system, when compared to the control group, had considerably more contrast illusions at set-testing stage and considerably bigger response time during attention shifting at set actualization stage. These data suggest a participation of fronto-thalamic system in set-forming and set-shifting.

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.

EEG coherence in the alpha and theta bands during set formation and testing was studied in healthy adult subjects (n = 35). The set was formed to pictures of faces with a negative emotional expression (an angry face). Different patterns of the EEG spatial synchronization were revealed for the theta and alpha bands, especially, in subjects who formed the rigid set (erroneous perception of the facial expression in the form of contrast and assimilative illusions). An increase in coherence in the theta band was observed in subjects of this group (n = 23) between the dorsolateral frontal and temporal regions of the right hemisphere. A neural mechanism underlying the visual illusions was suggested. Analysis of the EEG coherence in the theta and alpha bands makes it possible to obtain the "windows" for the insight into operation of the cortico-hippocampal and fronto-thalamic functional systems of the integrative brain activity and involvement of these systems in perception of facial expression. The fronto-thalamic system is involved in a more generalized activation of the brain cortex, especially of its frontal regions. The theta rhythm system seems to facilitate the integration of the frontal and temporal cortices of the right hemisphere and association of the right temporal region with the parietal and central regions of both hemispheres.

The effect of increasing working memory load (by introduction of an additional cognitive task into the experimental context) on the recognition of emotional facial expression in a visual set paradigm was studied in healthy adult subjects. The link between plasticity of the cognitive set to emotional facial expression and the working memory was revealed. It was found that an increase in the working memory load was associated with a delay of set shifting in a modified situation. The set became more rigid which appeared as increasing number of trials with erroneous assessments of facial expression in the form of contrast or assimilative illusions. The significance of inner states and priming for the insight into psychophysiological mechanisms of erroneous assessments under conditions of the working memory loading is discussed in terms of the concept of the integration of bottom-up and top-down streams.

Set-forming and set-shifting were studied in children of three age groups: five to six-, six to seven- and nine to ten-year-old. Set effect displayed itself in contrast illusions in most of the subjects (69 of 73). Age differences in set plasticity and in reaction time to a probe stimulus were revealed. Five to six-year-old children formed a more rigid set than older ones. According to EEG coherence function in theta- and alpha-bands and behavioral data, a hypothesis of two systems being involved in set-forming and set-shifting is proposed. These systems are: a fronto-talamic system of selective attention, and a system of cortico-hippocampal connections that are involved in cortical processing of novel visual information and in episodic memory. The age of 6-7 years is shown to be critical in forming a plastic type of cognitive set.

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.

Changes in the alpha-rhythm synchronization were revealed at different stages of cognitive visual set in 5- to 7-year-old children. We found a clear-cut correlation of these changes with set plasticity. In children with a plastic set, the EEG synchronization between the frontal and other brain regions substantially increased in the period of set-shifting (the actualization stage). At the set extinction stage, after set-shifting has already taken place, the EEG-synchronization becomes minimal. On the contrary, in children who formed a rigid set, EEG coherence considerably increases at the set extinction stage. This finding suggests that the rigid set still affects the cognitive activity even after (judging from oral reports) the set shift has been completed. The age-related differences in cognitive set formation clearly correlate with the time course of the EEG synchronization between the frontal and other brain regions. We think that the ability to form a plastic visual set depends on the frontal cortex maturation, which occurs at the age of 6-7 years, and its age-related effect on the brain cognitive functions.

The experimental evidence that the cognitive set shifting in healthy humans depends on the context of cognitive performance is discussed. Lability/rigidity of the experimentally formed unconscious visual set is largely determined by the type of additional task ("what?" or "where?", i. e., stimulus recognition or spatial localization, respectively) introduced into the context of the experiment. It is suggested that the acquired set more readily shifts to a new one more adequate to modified conditions in case of alternation of the ventral and dorsal visual pathways involved in the information processing in the context of cognitive performance.

Rigidity of a verbal set was compared in three series of experiments: (1) pseudowords were presented at the set-forming stage and were changed for common words at the testing stage; (2) in the same conditions as in 1, an additional task of target localization in the matrix by two distinctive features was introduced; (3) in the additional target localization task, the spatial component was strengthened whereas image recognition component was reduced. The results confirmed our hypothesis about the context-dependence of the rigidity of the visual set. This characteristic substantially depends on a working memory loading and cognitive tasks performed by a subject, in particular, the relationship between the degrees of involvement of the ventral and dorsal visual systems into the cortical processing of sequential verbal and nonverbal visual stimuli. The experimental paradigm can serve as a model for the investigation of the roles of the ventral and dorsal visual systems in the recognition function.

Healthy adults were examined in three series of experiments with formation of an unconscious visual set: 1) the set was formed by repeated presentation of pairs of unequal circles (control); 2) an additional task of recognition of words/pseudowords was introduced into the context of the set-forming trials; 3) in the task additionally introduced, a subject had to spatially localize a certain target letter in a letter matrix. Scores of stability of the visual set to circles were compared. Coherence of the cortical electric activity in the alpha band was analyzed. We revealed a significant decrease in stability (rigidity) of the nonverbal visual set in the series with the additional task of spatial localization of the target stimulus. On the contrary, the set rigidity increased in the series with additional recognition of the verbal stimulus. EEG coherence patterns and behavioral data suggest that successful cognitive performance that demands dynamic situation-dependent shifts of unconscious sets takes place under conditions of alternation of tasks involving, predominantly, either the ventral ("what?") or dorsal ("where?") visual streams and, respectively, anterior or posterior systems of selective attention.

A top-down processing model and the role of frontal and prefrontal cortex in the neural mechanisms of recognition of verbal and non-verbal visual stimuli, are discussed. Stimulus recognition is considered to be a result of integration of the bottom-up and top-down streams. The cognitive set phenomenon can be used for studying the downward control in the neurocognitive visual system and in functional organisation of stimuli recognition.

In order to reveal the character of motivation influence on the stability of the unconscious visual set, young adult healthy subjects were promised to be rewarded for correct solution of the cognitive task. A substantial increase in set stability was observed under conditions of augmented motivation of a subject to the result of his performance. Positive and negative aspects of the impact of the increased motivation of a subject on his cognitive activity at the stages of set formation and actualization are discussed.

The cognitive set can be formed in healthy humans (75 subjects have been examined) on the basis of the Müller-Lyer's visual illusion. The effect of this set is expressed as a contrast illusion similar to the effect of the set, which is formed on the basis of the real size of visual stimuli (pictures of circles). Time of the simple motor reaction to the probe stimulus (light spot) depends on the factor of set stability. In subjects with the stable set the reaction time and its variability are substantially longer than in persons with the unstable set. Analysis of correctness of perception of the visual stimuli and the reaction time shows that the set which has been formed at the unconscious level leads to a certain rigidity in cognitive activity. Thus, factor of lability/stability of sets is an important feature of human cognitive activity.

By means of backward masking, the time of perception of letter stimuli presented to the left and right visual fields, was determined in practically healthy persons who were given different doses of alcohol, and in patients with chronic alcoholism. Evoked electrical activity to the same stimuli was recorded in identical conditions. A small dose of alcohol (0.41 g/kg) increases in healthy subjects the time of perception of visual signals only if they are presented in the left visual field: a medium dose (0.82 g/kg) increases the time of stimuli perception in both halves of the visual field, but obviously more so in the left one, in patients with chronic alcoholism the time of perception is substantially longer in the left visual field. A small dose of alcohol does not affect evoked electrical cortical activity in healthy persons. Distinct regional differences are exhibited in the action of the medium dose of alcohol on the cerebral cortex of healthy persons. Evoked potential in the central area is depressed to a greater extent than in the visual and associative (Brodman field 37) zones. With chronic alcohol intoxication, evoked activity in the right hemisphere is depressed considerably more than in the left one.

Recording of averaged evoked potentials to two successive visual stimuli shows that associations, temporary connections, direct and feedback, can be elaborated in man between two unrecognized stimuli. The magnitude of cortical late response to the first stimulus in the complex diminishes as a result of action of the inhibitory feedback temporary connection. This inhibitory effect is more pronounced when the second stimulus is emotionally significant for the subject. The evoked potential to the second stimulus in the association between unrecognized visual stimuli is considerably facilitated. The role is discussed of direct and feedback temporary connections between unrecognized stimuli in some unconscious psychic phenomena in man.

Recognition of short time intervals (10, 60, and 180 ms) between visual stimuli presented to the left or right hemisphere was studied in adult healthy people. The interval of 180 ms is recognized better than that of 10 or 60 ms. Learning with repeated tests with 180 ms intervals proceeds better than that with short intervals. The predominance of the left hemisphere has been revealed only for perception of 10 ms interval. The other time intervals asymmetry is not observed. It is suggested that the left hemisphere is predominant in estimation of short (less than 60 ms) time intervals. In formation of time nervous model a significant role is played by local activation of the cortical zone where the standard stimulus is addressed.

11 right-handed subjects with normal vision were examined. The analysis of latencies and amplitudes of the late AEP components elicited by verbal stimuli, presented in different halves of the visual field, revealed that the late positive evoked potential P300 to a single word with neutral meaning develops in the right occipital area with a shorter latency and a greater amplitude, than in the left one. Interhemispheric differences are not observed in "the associative" zone (presumably at the junction of the temporal, parietal and occipital areas). In the process of perception of an emotional word interhemispheric relations are considerably changed: in the left occipital area the P300 wave latency is considerably shorter, than in the right one; no differences in the amplitude of P300 are visible. The changes in P300 wave latencies reflect a local nonspecific activation of the cortex, directly connected with the analysis of the emotional verbal signal. The obliteration of interhemispheric differences in P300 wave amplitude is largely due to background emotional excitation.

Averaged evoked potentials (AEP) to verbal (letters) and nonverbal (random shapes) stimuli exposed in the left and right visual fields were registered in healthy subjects with normal vision. Analysis of the later AEP latencies pointed to asymmetry in the temporal parameters of the interhemispheric interaction. The late AEP latency is shorter in the right hemisphere than in the left hemisphere. The difference is more pronounced in responses to nonverbal stimuli. The earlier development of the evoked potential in the right hemisphere (or the later one in the left hemisphere) accounts for the interhemispheric difference in the temporal parameters of the late AEP components. Comparison of the latency of the component P300 to verbal and nonverbal stimuli presented in the ipsilateral or the contralateral visual fields reveals a transfer of the results of the cortical processing of visual information in the course of interhemispheric interaction.

The wave P300 was recorded in both hemispheres in order to study interhemispheric differences in the process of perception of unrecognized verbal stimuli. The stimuli--unrecognized words, neutral and emotional--were alternately presented at random in the left and right visual fields. In response to an unrecognized emotional word, the amplitude of the P300 wave increases diffusely in both hemispheres, as compared to the response to a neutral word, with no changes in interhemispheric differences. They change considerably in the process of an "unaccountable" emotion, caused by an unrecognized word, due to unilateral activation of the right hemisphere. The conclusion is made on the predominant role of the right hemisphere in the cortical organization of such unconscious function as "unaccountable" emotion.

The study was made on healthy adult subjects. The reaction time of the hand (RT) was measured under two conditions: 1) the choice of reaction (right or left hand) is determined by the nature of the warning stimulus; 2) decision on the choice is taken, depending on the second, trigger stimulus. Stimuli are presented at random sequences to different visual fields. The reaction time to the visual signal presented to the visual field ipsilateral to the hand is significantly shorter (by 15 to 26 msec) than to the stimulus in the contralateral visual field. In a simple motor reaction, when no discrimination of trigger stimulus and the decision on the choice of reaction is required, a hemispheric asymmetry of reaction time is manifested: the left hemisphere only responds differently to direct visual stimulation and to that mediated through the contralateral hemisphere.

In healthy adult subjects recognition was studied of geometrical figures presented unilaterally, and of separate letters presented unilaterally and dichoptically to the right and left visual fields. At near-threshold exposition, separate letters are better recognized in the right visual field, than in the left one, regardless of the method of presentation. There is no asymmetry in recognition of geometrical figures. In conditions of backward masking asymmetry of perception of separate letters is likewise observed, but they are better recognized in the left visual field. This suggests that the perception time of separate letters is shorter when they are addressed "directly" to the right hemisphere.