[Dynamics of induced EEG in the intervals between a target and trigger stimuli during formation of a set to emotionally negative facial expression].

A visual set was used as a model to study the influence of the increased memory load on the recognition of facial expression in 70 healthy adults. In order to additionally load the working memory, we lengthened the time gap between target (faces) and trigger stimuli. Such a lengthening from 1 to 8 s resulted in an increase of set plasticity (fewer mistakes in facial expression recognition). It also led to a reduction of the reaction time and less number of contrast illusions in recognition. We analyzed theta- and alpha-band EEG changes during individual segments of the time gap and suggested that repeated trials with a certain fixed interval between stimuli formed an inner representation of the interval duration. This inner representation up-regulates the visual attention in case of anticipation of a relevant event (stimulus) and down-regulates the attention when the stimulus is not expected. In case of the plastic set, the induced EEG synchronization in the alpha band is stronger in the trials with correct recognition in the middle of the inter-stimulus time gap. We think this synchronization reflects the action of the top-down cognitive control that suppresses the influence of irrelevant information on the brain activity. Theta-band dynamics in the inter-stimulus time gap can be associated with the emotional strain caused by the fact that a person had to retain in memory (for several seconds) the result of facial expression recognition.

[Theta and alpha-band EEG spatial synchronization under the conditions of visual set, formed to an angry face expression. A study of 5-11-year-old children].

EEG coherence in theta and alpha bands during set-forming and set-shifting was studied in 5-6-year-old (n=18) and 10-11-year-old (n=25) children. Set was formed to visual stimuli (facial photos with emotionally negative expression). Younger children displayed smaller coherence values, especially in the right hemisphere, than older ones. We also revealed differences in theta and alpha band coherence in cases of a rigid and a plastic set. For example, EEG-coherence values were smaller when cognitive processes were relatively rigid (i.e., in a case of a slower set-shifting). A strong correlation between electrophysiological and behavioral data supports the hypothesis that cortico-hippocampal and fronto-thalamic brain integration systems participate in facial expression recognition and provide cognition flexibility.

[Cognitive control in recognition of emotionally negative face in 5-10-year-old children].

We used the experimental model of cognitive visual set, designed by D.N. Uznadze, to study the influence of previous experience on emotional face expression recognition in pre-school (6.1 +/- 0.3 years) and elementary school (10.5 +/- 0.1 years) children. Our results suggest that the ability to form a cognitive set to an angry face expression develops in ontogenesis in strong concordance with functional maturation of prefrontal cortex that takes place at the age of approximately 10 years. At this age children display almost the same level of set plasticity and a similar kind of erroneous perceptions during set actualization as grown-ups. Children of younger age (6.1 +/- 0.3 years) display more perceverative erroneous perceptions, or assimilative illusions (probably of a priming origin), than the above mentioned groups. We consider this to be a result of a more strong influence of previous experience in their case.

[Individual typological differences in human behavior under conditions of reward choice assoicated with risk].

A choice between probability (100, 75, 50, 25, 10, 0%) and valuable reward were investigated in adult. In behavioral experiments, adult subjects put in a situation of a choice between greater, but risky prize and smaller, but received always, made the decision according to situational factors and specific features of character such as propensity to risk and care. In a situation of choice of behavioral strategy, subjects could be divided in "inclined to risk" and "careful". Tipologycal differences between groups were the greatest under conditions of 25% probability of getting a valuable reward. Probability prognosis was more efficient in persons "tended to risk", than in "careful" subjects. According to psychological tests, "impulsive" people appeared to be more inclined to risk than to cautiousness. For the group of persons that tended to cautiousness under conditions of 25% probability of getting a valuable reward, synchronism of EEG rhythms in the alpha and beta bands was revealed.

[Changes in face expression recognition caused by additional visual-spatial load].

Changes in face expression recognition and EEG synchronization arising from additional load on working memory were studied in healthy adults. Two types of additional task--semantic and visuospatial--were used to load working memory in an experiment with a visual set, formed to facial stimuli. During perception of new facial stimuli, both these types of additional task caused an increase of erroneous face expression recognitions in the form of assimilative illusions. Alpha-band (8-10 Hz) EEG synchronization analysis revealed that additional memory load causes a decrease of frontal attention system input in set-forming and set-shifting. As for theta-band (4-7 Hz) synchronization, it changed ambiguously at additional memory load--in right fronto-temporal region coherence function decreased; other coherence connections, especially intra-hemispheric and in the left hemisphere, increased. At issue is the crucial role of fronto-thalamic and cortico-hippocampal systems in plasticity of visual sets formed to facial expressions.

[Induced cortical electrical activity during different time-spans between warning and target stimuli].

A certain alpha-band EEG dynamics was revealed in healthy adults (n = 16) at the interval between a warning and a target stimulus in a simple visuospatial task (subjects were instructed to locate a specific letter in the table of letters). Two series of experiment--either with a 2-sec or a 9-sec inter-stimulus interval were conducted, each consisting of 60 trials. In both series, we observed an induced desynchronization of low alpha (8-10 Hz) at the first second after the warning stimulus and its desynchronization just before the target stimulus. In series with a 9-sec inter-stimulus interval at the 4-6 s of it we observed an alpha-band synchronization, especially distinct in high alpha (10.5-13 Hz). This synchronization gradually reduced towards the end of the inter-stimulus interval. We consider the above changes in alpha-band spectral power during the inter-stimulus interval to be induced by "inner impulsations" caused by an internal representation (set) of the stimuli time-sequence. Changes in the level of cognitive control during the inter-stimulus interval cause increases and decreases in fronto-thalamic system activity, which are manifested in changes of alpha-band spectral power. Analysis of theta-band dynamics suggests that cortico-hippocampal system doesn't participate in this process.

[EEG spatial synchronization at different set stages in 8-year-old children with different levels of selective attention fronto-thalamic system maturity].

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.

[Spectral power of theta and alpha EEG-bands in preschool children with different level of set plasticity].

Spectral power of theta and alpha EEG-bands at different stages of visual set was studied in 5-7-year-old children. Children with a plastic set had greater alpha-band spectral power values than children with a rigid set. At set formation stage children with a rigid set displayed an increase of theta-band EEG-power, which is a manifestation of "immature" arousal reaction. Children with a plastic set displayed at set formation stage an increase of alpha-band spectral power in bilateral occipital brain areas. Dynamics of EEG spectral power differed in children before and after 6 years of age. At set formation stage 5-6-year-olds displayed an above-mentioned "immature" arousal reaction, and 6-7-year-olds--an increase of alpha-band spectral power in occipital brain areas. At set actualization stage 6-7-year-olds displayed an increase of alpha-band spectral power in right posterior brain areas. At set extinction in this group a bilateral decrease of alpha-band spectral power in mid-frontal areas was observed. An importance for a quick set-shifting of certain brain areas' involvement in the process of visual perception is discussed.

[Context effects recognition of the emotional facial expression].

Influence of additional working memory load on emotional face recognition was studied in healthy adults. Visual set to emotional face expression was experimentally formed, and two types of additional task--visual-spatial or semantic--were embedded in the experiment. Additional task caused less plastic set, i.e., a slower set-shifting. This effect displayed itself in an increase of erroneous facial expression perceptions. The character of these erroneous perceptions (assimilative or contrast or visual illusions) depended on the type of the additional task. Pre-stimulus EEG coherence across experimental trials in theta (4-7), low alpha (8-10 Hz) and beta (14--20) bands was analysed. Data of low-alpha and beta-coherence supported the hypothesis that increased memory load caused less involvement of frontal lobes in selective attention mechanisms that are associated with set-forming. This results in a slower set-shifting. Increased memory load also led to a growth of theta-band coherence in the left hemisphere and its decrease in the right hemisphere. The account of theta-coherence decrease in the right hemisphere between prefrontal and temporal areas for a slower set-shifting is discussed.

Synchronization of EEG theta and alpha rhythms in an unconscious set to the perception of an emotional facial expression.

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 and shifting of selective attention in 8-year-old children with EEG-signs of immaturity of fronto-thalamic and brainstem activating systems].

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.

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.

Spatial organization of cortical electrical activity at different stages of a visual set in preschool and early school age.

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.

[Dependence of plasticity of set to emotional facial expression on working memory load].

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.

[Alpha- and theta-bands spatial synchronization in unconscious visual set formed for perception of emotional facial expression].

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.

[Cognitive set as a regulation factor in recognition of emotional facial expression].

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.

[Spatial synchronization of cortical electrical activity at different stages of visual set in preschool children].

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 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.

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

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 nonverbal set in preschool- and schoolchildren].

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.