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Biomedical subjects

E A Cheremushkin

Publications and source records attributed to E A Cheremushkin.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

[Interhemispheric asymmetry of the spatial-temporal potentials of the human cerebral cortex under various conditions of the formation of verbal conditioning].

It was shown on the basis of electrophysiological data in 60 healthy subjects that the interhemispheric brain asymmetry in the course of formation and actualization of the verbal set depends on the context of the cognitive activity. More complex cognitive activity results in a development of regional interhemispheric differences in the studied characteristics of the spatiotemporal organization of cortical potentials. These differences are most spectacular in the frontal areas of the cortex.

Adult↗
PubMedDate not supplied

[Changes in the cortical electric activity in the course of set formation under conditions of increased loading of the working memory].

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.

Adolescent↗
PubMedDate not supplied

[Cognitive set depends on the involvement of the ventral and dorsal visual systems].

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.

Adult↗
PubMedDate not supplied

[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.

Age Factors↗
PubMedDate not supplied

[Emotionality and spatio-temporal organization of momentary EEG potentials].

With the aim to reveal features of the neocortical spatiotemporal organization of potentials characteristic of different genetically predetermined emotional levels, momentary values of EEG potentials were analyzed in inbred rats of MR and MNRA strains. A topogram was described by a basic parameter such as its general level (the mean of momentary values of potentials derived from 24 symmetrical electrodes bilaterally implanted into the brain cortex) and a similarity coefficient (correlation between the set of its momentary values and that of a standard topogram). The general level and similarity coefficient values were calculated for a series of successive topograms individually for the right and left hemisphere. Also, right- and left-side power spectra of these series were calculated. In rats of MR strain, significant (p < 0.05) peaks in the general level and similarity coefficient spectra were observed in the delta (2.0 Hz), teta (6.5 Hz) and alpha (9 Hz) frequency bands. In this strain, the general level power was higher at the right side, and the similarity coefficient power displayed the left-side dominance. In rats of MNRA strain, peaks in the delta(2.0 Hz) band coinsided in the general level and similarity coefficient spectra, whereas, independently, the general level spectra had peaks in the theta band (7.0 Hz), and similarity coefficient had peaks at frequencies 3.0, 4.5, and 6.0 Hz. The left-side general level spectral power was higher than the right-side general level spectral power in the delta and lower in the high-frequency theta bands. The similarity coefficient power displayed the left-side dominance for the peaks in the delta (2.0 Hz) and theta (3.0 Hz) bands, and it displayed the right-side dominance for the peaks in the theta (4.5 Hz) band. The specific features of the cortical spatiotemporal organization of potentials revealed in rats of MR and MNRA strains suggest different modes of functioning of at least two systems, reticulo-thalamo-corticaland hippocampo-cortical.

Animals↗
PubMedDate not supplied

[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.

Adult↗
PubMedDate not supplied

[The role of emotional-motivational processes in the mechanism of "insight" in the recognition of a latent visual image].

The task of the study was to determine the influence of emotional-motivational sphere on the phenomenon of out-of-logic mental activity. An accepted in laboratory model of recognition of concealed image in double image pictures was used. The electrical activity, recorded was analyzed by means of the method of computation of coefficient of community, elaborated in the laboratory, the results were presented in the from of stereometric map. The obtained results testify to the fact that emotional-motivational processes influence the mechanism of out-of-logic form of making solution; at out-of-logic form of making solution subjective evaluation of results dominates, what is reflected in the character of spatial distribution of coefficient of community.

Adult↗
PubMedDate not supplied

[Context-dependent EEG spectral characteristics during performance of tasks].

Spatial and frequency EEG characteristics of two groups of healthy adult subjects were examined in two series of experiments, which differed in conditions of the second cognitive task in a trial. The first task was the same in the two series: subjects had to evaluate size relationship between two closely spaced circles. The second task successively presented in trials of the first series consisted in the recognition of words/pseudowords, and in the second series, subjects had to localize a target letter in a matrix. It was assumed that the cognitive performance in the first series predominantly involved the ventral visual system, whereas during task performance in the second series, predominant involvement of the ventral and dorsal visual systems alternated. Multichannel EEG fragments recorded prior to the presentation of the task pairs were analyzed. Analysis of variance of the EEG spectral power revealed the generalized significant effect of the factor of the second task in the pair for delta band and lower beta subband, the power being higher in the first series. Factor brain hemisphere had a significant effect for the alpha band in the occipital area, the spectral power being lower in the left hemisphere for both experimental series. The task x hemisphere interaction was significant in the temporal cortical areas for the EEG power in alpha2 band, i.e., the predominant involvement of the ventral visual system was associated with stronger asymmetry of alpha2 rhythm and lower spectral power in this band in the left temporal area. Thus, the character of the forthcoming cognitive activity was shown to be reflected in spatio-frequency characteristics of the preceding EEG.

Adult↗
PubMedDate not supplied

[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.

Age Factors↗
PubMedDate not supplied

[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.

Adult↗
PubMedDate not supplied

[The role of the extralogical form of thinking in cognitive activity].

The aim of the study was an attempt to record neurophysiological processes connected with the mechanism of subconscious brain activity. Created in the laboratory method of construction of a topographical map of electrical processes interactions in 24 recorded points was applied. The obtained data testify that identification of evident and latent images in "double image pictures" is accompanied by similar relief of topomaps of interactions. Effect of "sudden vision" of latent image in a manner of "insight" is gradually prepared neurophysiologically, but is not realized by the subject and only at the last stage reaches the consciousness and is verbalized.

Adolescent↗
PubMedDate not supplied

[Systems organization of the electrical activity of the brain in recognizing a visual image based on data from the mapping of interconnection indices].

Eight subjects were studied by the method of topographic mapping of interconnection characteristics of the human brain electrical activity in the process of recognition of visual images. The method used in our studies differs from others by the fact that properties of the processes interconnections are mapped but not the characteristics of the very processes. Under recognition of images the relief of topographic map of interconnections of cortical electrical processes increases in the right and decreases in the left frontal areas. Thus both hemispheres participate in this process. The hypothesis is suggested about two types of spatial synchronization: of similar electrical activity and of the activity differentiated in the brain sections. The developed method proved to be informative for the studied structure of spatial-temporal organization of the human brain electrical activity.

Adolescent↗
PubMedDate not supplied

[The reflection of the augmenting-reducing phenomenon in the characteristics of the spatial-temporal EEG indices].

Phenomenon of augmenting-reducing was studied based on Livanov's concept on the spatial synchronization of biopotentials, multi-channel EEG recordings being used. Augmenting-reducing phenomenon is a certain type of response to any coming information. When single light flashes of increasing intensity were applied to 21 human subjects the phenomenon under study displayed wide spatial distribution. In experiments with rhythmical light stimulation the leading role of the spatially limited bioelectrical processes was shown. About 50% of the subjects retained interhemispheric asymmetry in the course of an experiment.

Brain Mapping↗
PubMedDate not supplied

[The mechanisms of uncognizable perception controlling human behavior].

The task of the study was to determine the influence of emotional-motivational sphere on the phenomenon of out-of-logic mental activity. An accepted in the laboratory model of the recognition of a hidden image double image pictures was used. Recorded multichannel EEG was analysed by the method of computation of coefficients of community elaborated in the laboratory. The results of computation were presented in a form of a stereometric map. The obtained results testify to the fact that the emotional-motivational processes influence the mechanism of the out-of-logic form of decision making. At the out-of-logic form of decision making a subjective evaluation of results dominates being reflected in the character of the spatial distribution of coefficient of community.

Adolescent↗
PubMedDate not supplied

[The characteristics of the spatial-temporal organization of the cortical potentials in the free-moving rabbit during training (a comparison of the stages in the generalization and specialization of the conditioned-reflex response)].

Analysis of successive topograms was applied to investigation of peculiarities of the spatio-temporal organization of cortical potentials of a rabbit at different stages of conditioning. Qualitative distinctions were shown between the stages in the character of regulation of the spatial synchronization (SS) related to variations in cortico-subcortical relations. Higher SS level at the stage of generalization changed for more complicated pattern of the spatio-temporal organization of cortical potentials. These complex spatio-temporal characteristics favoured facilitation of excitation spreading along the paths which provide specialization of the conditioned response under the action of the conditioned stimulus. Obtained results were correlated to specific membrane and synaptic modifications in the course of conditioning. The findings extend the notions of the cellular mechanisms which determine the features of the cortical SS at the stages of generalization and specialization of the conditioned reflex.

Animals↗
PubMedDate not supplied

[The effect of set on 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.

Adult↗
PubMedDate not supplied

[A comparison of the restructurings in the spatial-temporal organization of the cortical potentials from the human cerebral hemispheres with the EEG frequency characteristics during the solving of a cognitive task].

Spectral characteristics of the local and global EEG spatial-temporal organization were studied in 10 healthy subjects during solving the complicated intellectual tasks. Techniques of evaluation of successive topograms and point frequency mapping were applied. Two different types of the global spatial-temporal organization of brain potentials were observed. Increased delta in EEG spectra characterized the task solving. The alpha- and beta-rhythms occupied the limited part of the cortex. Point mapping enabled clarification of the spatial distribution of the dominant spectral frequencies and their redistribution under different functional loads. Comparison of the characteristics of the spatial-temporal organization of global bioelectrical processes and maps of the dominant rhythms in EEG power spectra made it possible to reveal the new relations in bioelectrical processes.

Adult↗