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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.

In healthy adults (n = 35) was used the model the set study of recognition angry facial expression. The load on working memory by extending the interstimuli time up to 16 sec between the target (facial image) and starting (spot light) stimuli does not lead to a significant slowdown of switching of the set. Differences in the magnitude of the induced synchronization of the alpha rhythm in interstimulus period obtained in the subjects with the change in recognition of emotional facial expressions and the subjects "without errors". At the last group synchronization is clearly more pronounced. The implementation of successive cognitive acts is modulated by selective attention, whichis evident in the level of changes the induced synchronization/desynchronization of alpha range potential. The proposed mechanism "inhibitory control" provides the flexibility of cognitive processes by suppressing effect on cortical processes irrelevant factors during interstimulation pauses. This "protective" mechanism, we believe due to little effect of the loading on working memory.

In a series of studies of influence of past experience on an recognition of emotionally negative facial expression where obtained experimental facts which we consider as the formation signs of under certain conditions high-plastic cognitive (flexible) sets ("not fixed sets", according to D.N. Uznadze) when there switching or updating was not accompanied by illusory distortion of recognition. The studies of this form of set revealed: 1--the induced reaction of synchronization of a teta-rhythm to target stimulus was larger, than in cases with rigid set; 2--the induced reaction of an alpha rhythm to target stimulus is expressed in its synchronization, at the others cases--in a desynchronization; 3--at increase in a time interval between target and trigger stimuli observe alpha rhythm synchronization in the prestimulus period and in time intervals between them, at other cases it wasn't observed; 4--at children this form of set observed at the age of 10-11 years when "mature" set on an facial expression is formed.

The model of cognitive set to emotionally negative facial expression was used in the study (35 young healthy subjects) of EEG events in a 8-second interval between the target and triggering stimuli. Coherence of brain potentials recorded from different cortical areas of the right and left brain hemispheres in the alpha and theta bands was analyzed in time segments within pre- and poststimulus intervals. A certain dynamics in the spatial synchronization in the alpha-band was revealed, which might reflect modulation of selective attention in time periods of the cognitive process providing its plasticity and set shift in response to a change in the situation. It is suggested that the source of attention modulation is the inner representation of the intervals between significant stimuli formed in the prefrontal cortex as a result of learning. Analysis of changes in the spatial synchronization in the theta band at individual stages of the set to angry face suggests that the corticohippocampal system is not directly involved in the time interval estimation but is linked to the emotional memory.

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.

The effect of increased working memory load (introduction of additional cognitive task into the context) was studied in adult healthy subjects (n = 35, 16 men, 19 women) in experiments with cognitive set. The EEG coherence in the frequency bands theta (4-7 Hz) and alpha (8-13 Hz), as well as alphal (8-10 Hz) and alpha2 (11-13 Hz) was analyzed and compared to the control data obtained in the experiments without additional memory load. Additional memory load was accompanied by an increase in the rigidity of the set to facial expression and substantial change in the pattern of the spatial synchronization of cortical potentials: coherence of potentials in the theta bands increased between the left and right frontal areas and between the frontal and temporal areas. A hypothesis is suggested that the rigidity of the set to emotionally negative facial expression is associated with the activation of the cortico-hippocampal system, which is justified by a substantial increase in coherence in the theta band in the frontal area known as the key structure in the functioning of cognitive sets. Loading the working memory is associated also with substantial weakening of the spatial synchronization of the low-frequency alpha rhythm, which presumably reflects the increase in the role of the fronto-thalamic system of selective attention in the process of recognition due to redistribution of attention induced by the additional cognitive task included in the context of current activity of a subject.

Visual cognitive set was studied in two groups of 8-year-old children: with normal development of fronto-thalamic system (FTS) (n = 21) and with functional immaturity of this system (n = 29). In most of the children with the FTS-immaturity a formed visual set was rigid. EEG was recorded from the frontal, central, temporal, parietal and occipital regions, and coherence function in theta-, alpha- and beta-bands was analyzed. The most vivid differences between two groups of children were revealed at the set actualization stage. If the set was a plastic one, the value of coherence function between frontal and dorsal areas was higher in children with FTS-immaturity, than in "normal" ones. In the group with FTS-immaturity the dependence of coherence function on the set's plasticity was more vivid, than in children without FTS-immaturity. In all children with a rigid set value of coherence function was higher during set formation, actualization and extinction, than at resting condition with eyes opened. In the group with FTS-immaturity the coherence of theta-band considerably increased at the set actualization stage, mainly in the right hemisphere. We consider this to be the evidence of a comparatively bigger role of cortico-hippocampal system and implicit episodic memory the set shifting. Probably these processes compensate the FTS-dysfunction and make a set more plastic.

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.

Alpha- and theta-band EEG synchronization/desynchronization, induced by the presentation of emotionally negative stimulus (angry faces), was studied in 35 healthy adults. In subjects with a plastic set induced theta-synchronization was greater, and its latency was shorter, than in subjects with a rigid set. This difference is particularly apparent in temporal and parieto-occipital brain regions. A sufficiently high level of theta-synchronization is essential for a quick set-shifting. This synchronization reflects the activity of cortico-hippocampal feedback system and its participation in the perception of emotional faces. In subjects with a plastic set this process induces alpha-synchronization, and in subjects with a rigid set--desynchronization. W. Klimesh (2007) suggests, that induced alpha-synchronization reflects processes of inhibition in cognitive activity. This inhibition plays an important role in the set-shifting. The role of tonic and phasic forms of cortex activation, produced by cortico-hippocampal and fronto-thalamic systems, in the shifting of a cognitive set to facial face expression is discussed.

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.

Coherence function of the EEG in the bands of 8-13 (alpha rhythm) and 14-25 Hz (beta rhythm) was analyzed in 35 healthy adult subjects during formation and testing of a visual cognitive set to pictures of faces with different emotional expressions. The intra- and interhemispheric coherences of the potentials in the frontal area and coherence between the right frontal and temporal derivation were shown to increase at the stage of set actualization. The results of the analysis confirm the suggestion that the frontal cortical areas are predominantly involved in formation and actualization of the set to facial emotional expression. The conclusion is based on the idea that the spatial synchronization of the brain electrical potentials is an index of the functional relations between the corresponding cortical areas and their cooperative involvement in a certain kind of activity (their simultaneous activation).

Effect of previous experience on the function of recognition of emotional facial expression was studied with the model of an unconscious visual set. It was found that repeated perception of pictures of face with angry expression caused a substantial effect on subsequent recognition of emotional facial expression. Recognition could be distorted, and expression of the face with "neutral" expression could be erroneously perceived as emotionally negative. Both contrast and assimilative illusions were observed. Evidence is presented that the described effect is the result of the set formation to emotional facial expression. The involvement of the prefrontal cortex into the structural-functional system of facial expression recognition is discussed. Kettel's test revealed significant correlations between the factor of rigidity of the set to emotional facial expression and the scores of personality traits such as social boldness--shyness on the H Scale, on the one hand, and the level of anxiety on the other.

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.

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.

Visual set for perception of unequal circles was formed in 5-6-year-old preschool- (n = 30) and schoolchildren (n = 43). Children of 5.3-6.1 years old formed a less rigid set than 9-10-year-olds. The reaction time to a probe stimulus significantly depended on the set stability and stage. The role of structural maturation of the frontal cortical areas in set formation and stability is discussed. The factor of set rigidity was shown to be significant for cognitive activity.

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.

Ivan Solomonovich Beritashvili (Beritov) is one of the great Russian physiologists who have created the Russian route of the modern science of behavior. He has proposed and experimentally substantiated a concept of psychoneural activity according to which the behavior controlled by images is the main and higher form of the behavior of vertebrates. Behaviors on the basis of conditioned reflexes and images are qualitatively different activities underlain by different neural substrates. Recently, the Beritashvili's principle ideas have been confirmed by multiple experimental studies of the animal and human cognitive behavior. At present, the concept of the procedural memory formed by training and acquisition and episodic memory formed on the basis of images is commonly accepted. The episodic memory stores the environmental events and phenomena perceived by an animal or a human. Each time when the image is reproduced during perception of environment or its part, an animal performs the same behavioral act as during the actual perception. Beritashvili's viewpoint that the procedural and declarative memories are controlled by different brain structures has been confirmed by experiments.

Stability of the cognitive set to nonsense words in healthy adult subjects was compared in two experimental conditions: (1) subjects had only to recognize pseudowords/words; (2) in each trial after the pseudoword/word recognition, subjects had to press a button in response to a visual probe stimulus and only after this action to pronounce a recognized pseudoword/word. It was shown that complication of the cognitive performance in the second condition did not affect the set rigidity. However, the pattern of the cortical electric activity substantially changed: the EEG power in the theta frequency range and coherence function, in particular, interhemispheric, in the frontal cortical areas were higher in the second condition. The increase in coherence function in the frontal areas was most pronounced in the theta and alphal ranges. It was suggested that increase in activity of the frontal regions of the brain cortex facilitates shifts of visual sets under increasing load of the working memory.

The importance of Asratyan's conditioned switching-over phenomenon as an experimental model for investigation of the control function of the inner states (sets) in behavior is discussed. It is argued that experimental investigation of the animal conditioned switching-over phenomenon at the novel cognitive stage of exploration of neural mechanisms of behavior using the modern conceptual models of brain operation and conceptual apparatus can be a promising approach to understanding of the physiological basis of human unconscious cognitive sets and their role in perception of external signals and organization of voluntary behavior.

Analysis of EEG coherence performed in 60 healthy adult subjects revealed some changes in the spatial organization of cortical electrical activity produced by complication of the context of cognitive performance (increasing the working memory load). Changes in the degree of coherence of cortical potentials within the local areas were observed already at the stage of the "operative readiness" immediately after the instruction, i.e., representation of the cognitive task sequence in the explicit working memory. The observed changes were different in the anterior (decrease in the degree of coherence) and posterior (increase in coherence) areas of the cortex. Context-related increase in the local coherence was more pronounced in the temporal, parietal, and occipital areas of the left hemisphere than in the right hemisphere.

It was found in healthy adult subjects (n = 90) that under conditions of complication of cognitive tasks (increasing number of relevant stimuli), the stability (rigidity) of the unconscious cognitive sets markedly rises. These changes in both verbal and nonverbal sets depend on the working memory loading. The revealed dependence of the motor reaction time to the probe stimulus on the sequence of the set stimuli in a context and on the set stage suggests that unconscious cognitive sets can regulate selective attention.

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.

It was shown in adult healthy subjects (n = 60) that the set depends on the context of cognitive activity. Under conditions of its complication, when a subject had to solve successively several tasks, the stability of the verbal set markedly increased. This was expressed in a longer effect of "blindness" characteristic for the set to pseudo-word reading and increase in the time of reaction to a probe stimulus.

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.

A psychological set was formed in 30 healthy adult subjects by means of successive exposition on the screen (with the intervals in 3-7 sec) of 30 single pseudo words written in the Latin letters. This series of stimuli was immediately followed by similar presentation of 36 single Russian words which consisted of the letters written in the same way as some characters of the Latin alphabet. At the beginning of the second train of stimuli all the subjects began to read the well-known Russian words as senseless. In 11 subjects this effect disappeared after 1-2 Russian word presentations and in 19 subjects only after 6-36 presentations. Analysis of the reaction time to the presentation of the visual probe stimulus suggests that the formation of preparatory set improves selective attention to the stimuli acting in a given situation and thus consolidates the cognitive processes.

Regulatory function of the set in human cognitive activity and organization of behaviour is discussed in the paper. The effect of the set is revealed by means of recording auditory event-related potentials in "oddball"' paradigm. Such kind of experiments give an opportunity to study not only phenomenology, but psychophysiological basis of this mental phenomenon.

The key point in the psychophysiological study of consciousness is the problem of finding out qualitative differences in reactions (event-related potentials) on recognized and unrecognized verbal and nonverbal stimuli. The role of the neural mechanisms of focused attention and the functional hemispheric asymmetry in neurobiology of consciousness is discussed.

The interstimulus intervals (10, 60 and 180 ms) discrimination were studied in psychopaths and subjects with psychopathic features (accentuated individualities after Leonard). Event related potentials to visual stimuli (successively presented strips with above mentioned intervals) were recorded. Essential intergroup differences were found in the cognitive performance and its dynamics. The deterioration of cognitive processes, learning deficiency and P300 decrease manifested by psychopaths allow to propose the existence of inherent or acquired pathology of the limbic brain, a key structure of the motivational and emotional behaviour.

The formation of late evoked cortical responses, N150 and P300, correlates with some factors determining cognitive activity (selective attention, different types of memory, decision making process). Influence of different significance stimuli in a particular situation results in creation of an integral "psychonervous image" reflecting a context of these stimuli, whole complex of cognitive tasks to be solved. It influences significantly on the magnitude of cortical evoked reactions to different stimuli that allows to make a correspondence with the "psychological set" phenomenon and its role in the evaluation of the perceived stimuli.

Neural mechanisms are considered of such unconscious psychic phenomena as subliminal perception of semantic stimuli, psychological defence, unaccountable emotions. The results are given of many years studies conducted by means of conditioned, electrophysiological and psychophysiological methods. The possibility is proved of semantic analysis of perception on unconscious level and formation of association with the help of unrealized emotionally significant words. At present it is possible to describe only few neural mechanisms of consciousness and unconsciousness; however, the development of contemporary psychophysiology allows to state that the analysis of this problem from scientific positions is the most correct way to learn the nature of the brain processes which are the basis of these complicated psychic phenomena.

In adult emotionally excitable persons the role was studied of unrecognized reinforcement forms in the function of differentiation of time microintervals. As feedback stimuli the word "good" (positive reinforcement) and a word connected with negative emotions of the subject (negative reinforcement) were applied. Experimental confirmation was obtained of the hypothesis that unrecognized phenomena of environment can influence conscious psychic activity, the process of man learning. Unrecognized semantic stimuli can function as a reinforcing factor and in this way participate in the process of learning of cognitive activity realized at conscious level.

A number of experiments shows that the character of human cortical response to a conditioned stimulus is to a considerable degree determined by properties and significance of the second stimulus in the combined pair. In a combination of two stimuli differently expressed depression of cortical response to the first stimulus takes place. If the "reinforcing" stimulus is emotionally significant and is recognized then the changes of evoked cortical activity in response to conditioned stimulus are complex and of different signs; they result from simultaneous action on cortical structures of both inhibitory and activating "nonspecific" influences. In this case the facilitation of the cortical response is revealed by comparison with the tests of indifferent stimulus before pairing or with tests where association between two indifferent stimuli is formed. A considerable increase of evoked response after elimination of the "reinforcing" emotional stimulus testifies that this facilitation is merely relative, and along with activating influence via feedback has an inhibitory action on cortical structures which perceive the conditioned stimulus.

In elderly people, in comparison with the young ones, the latency of wave P300 is increased in response to all applied acoustic signals, the amplitude of P300 is lower only in response to significant stimuli. No age changes of the wave N150 parameters are noticed. P300 (or N150) wave amplitude depends on signal significance of the sound; it is the lowest in response to significant stimuli and the highest to the ignored ones. Possible reasons of this paradoxical phenomenon are discussed. Preferential participation of different stages of cortical information processing is determined by the difficulty of perceptive task solution. Cortical electrical reaction to separate stimuli is significantly determined by the context of the information perceived in the given period, creating psychological state of the personality.

Two parts of a geometrical figure are consecutively presented to healthy adult subjects in the left and right visual fields; the subjects have to compare them mentally and to decide whether these parts form a standard figure or not. Correctness of the reaction is controlled by a computer which lights up on the screen the words "good" or "error". The number of correct decisions of this visual-spatial task does not depend on the hemisphere to which information is addressed. The reaction time is substantially shorter if the information comes "directly" to the right hemisphere. Due to better training in the left hemisphere interhemispheric difference in reaction time gradually disappears in repeated tests. Training to mental "constructing" takes place only in the tests following positive feedback stimulus. Analysis of amplitude-temporal parameters of P300 wave shows that at correct decision of the visual-spatial task the level of activation in the right hemisphere is higher than in the left one.

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.

Reaction time was recorded in adult healthy people at pauses of 80, 110, 150, 200, 300, 500 and 800 ms between the warning and the triggering stimuli. The warning signal determined the choice of reaction. The stimuli were presented to different halves of the visual field at random. 200 ms pause between the warning and the triggering stimuli is critical for the reaction time. Beginning with this interval, the reaction time was considerably reduced. When information from the triggering stimulus reached "directly" the hemisphere which was "to produce" the motor response, reaction time was considerably shorter, than at non-coincidence of these two factors. The influence of their combination on reaction time is particularly pronounced at 150-500 ms pauses between the warning and the triggering stimuli. The data obtained suggest that the decision making results in a lateralized activation of the hemisphere, which is "to produce" the motor reaction. As a rule, reaction time is not influenced by spatial location of the warning signal. The results of the work should be taken into account when organizing activity of an operator.

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.

The analysis of the late positive wave (component P300) of an averaged evoked potential, recorded to visual stimuli in different experimental situations has shown that local activation of the cerebral cortex during conscious experience (Pavlovian "light spot") is of a dynamic nature and is determined by signal significance of stimuli and predominant voluntary activity. In cases when it is necessary to decide on the choice of reaction anterior areas of neocortex are activated. If the function of perception is dominating the local activation essentially occurs in corresponding cortical area at which the perceived stimulus is timed. The cortico-thalamo-cortical mechanism of focused attention and its role in providing for conscious human experience is discussed.

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.

The influence of seduxen (diazepam) on cortical potentials P300 evoked by neutral and emotional words was studied in adult subjects having life conflicts. The therapeutic dose of seduxen (10 mg) had no significant effect on the amplitude of the late positive cortical response P300 to neutral words. Seduxen depresses the emotional activation of the cerebral cortex; that is manifested in selective elimination of those changes in latency and amplitude of P300 wave which are observed in response to emotionally significant words. Under the action of seduxen, the interhemispheric difference in the latency of cortical response disappears due to latency increase in the right hemisphere.

Average evoked potentials (AEP) were recorded in practically healthy subjects to "meaningless" figures and letters, presented to different halves of the visual field. Analysis of the amplitudes of AEP late components to verbal and non-verbal stimuli reveals hemispheric asymmetry. A higher amplitude of the late positive evoked response (P300) to a "direct" stimulation both by verbal and non-verbal stimuli (in the contralateral field of vision) is recorded in the left hemisphere than in the right one. Similar stimulation of the right hemisphere does not reveal sucha difference. In the left hemisphere the P300 wave is of a clearly greater amplitude to a "direct" stimulation (contralateral visual field) than to an "indirect" one (ipsilateral visual field), regardless of the nature of the stimulus. No such difference is observed in the right hemisphere. The magnitude of the late negative wave (component N200) to non-verbal stimuli is greater in the right hemisphere both in response to "direct" and "indirect" stimulations. No intrahemispheric difference has been found in the amplitude of late evoked responses of the cerebral cortex to verbal and non-verbal stimuli.

The study was made on adult humans in a conflict situation. A combination of a non-verbal visual stimulus with an unrecognized emotional word substantially changes interhemispheric functional relations. The latency of the P300 potential in response to the first stimulus becomes reduced in the left occipital area. The potential amplitude considerably diminishes in all the recorded cortical areas (occipital, associative and central), but the reductions more pronounced in the left hemisphere. The nature of the P300 wave changes in response to the conditional stimulus is determined by psychophysiological properties of the "reinforcing" stimulus, in particular by its being non-recognized. Conditioned changes of the P300 wave in tests, where the "reinforcing" stimulus is not recognized, are very stable, and are not extinguished, despite repetitive presentation of the signal without combining it with the emotional word.

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.