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Biomedical subjects

E A Cheremushkin

Publications and source records attributed to E A Cheremushkin.

At least 19 recordsLinked to original sources
PubMed2006

Dependence of the cognitive set on the involvement of the ventral and dorsal visual systems in cognitive activity.

Measures of the stability of a non-verbal visual set were compared in healthy human subjects in three series of experiments: 1) controls, in which a pair of set-forming stimuli (images of circles) were presented; 2) in the context of a test with a non-verbal set, subjects were presented with an additional task consisting of recognition of pseudowords (words); and 3) as before, but the additional task consisted of identifying the position of a target stimulus in a matrix of letters. There was a significant decrease in the stability (rigidity) of the non-verbal set on introduction of the additional task consisting of identifying the spatial position of a target stimulus; conversely, there was an increase in rigidity when the task consisted of recognizing the quality of a stimulus. Coherence analysis of cortical potentials in the alpha range showed that changes in the spatial organization of cortical electrical activity were significantly different, depending on the nature of the additional task: when the additional task involved recognition of a verbal stimulus, coherence connections were strengthened in the frontal-temporal-parietal areas of the right hemisphere; presentation in the context of a visuospatial task resulted in greater changes being observed in the anterior areas of the right hemisphere. It is suggested that the successful performance of mental functions requiring relatively rapid shifts in unconscious sets on changes in situation occurs in conditions of alternation of different types of cognitive tasks when cortical processing of visual information is mediated predominantly by one of the visual systems - either the ventral ("what?") or the dorsal ("where?") and, correspondingly, with the involvement of the anterior and posterior cortical selective attention systems.

Adult↗
PubMed2006

Emotionality and the temporospatial organization of instantaneous EEG potentials.

The characteristics of the temporospatial organization of cerebral cortical potentials at different levels of genetically determined emotionality were analyzed by constructing topograms of instantaneous EEG levels in the inbred rat strains MR and MNRA. Two parameters were calculated for each topogram: the total level and the similarity coefficient. Power spectra were calculated for the values and these were found to change in an oscillatory manner. Interstrain differences were found in the correlated changes in total levels and similarity coefficients, in the durations of changes in the total level, which were more marked than those of similarity coefficients, and the nature of interhemisphere asymmetry. In MR rats, the power spectra of both measures showed significant peaks with modes at 2.0, 6.5, and 9.0 Hz. In MNRA rats, peaks in the spectra of these measures both coincided (2.0 Hz) and differed (7.0 Hz in the spectrum of the total level and 3.0, 4.5, and 6.0 Hz in the spectrum of the similarity coefficient). These data suggest different types of functioning of the reticulothalamocortical and hippocampocortical systems in rats of these strains.

Animals↗
PubMed2006

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.

Adaptation, Psychological↗
PubMed2005

[Melanoma cell lines as the basis for antitumor vaccine preparation].

The aim of the study was to obtain cell lines from tumor samples, and to determine phenotypic cell characteristics in order to choose the optimal line for vaccine preparation. 15 cell lines with stable growth, varying in cultural growth character and cytomorphology, were obtained from samples taken from patients with metastatic skin melanoma. Immunofluorescense method was used to determine the expression of T- and B-lymphocyte markers, antigens of major histocompatibility complex (MHC) class I and II, and CD86 co-stimulating molecule in the cell lines. The expression of melanocyte differentiation antigens and cancer/testicular antigens was evaluated using immunocytochemical assay. The results allowed the authors to distinguish three types of melanoma cell lines according to the expression of MHC molecules: MHC-negative; MHC class I positive; MHC classes I and II positive.

Antigens, Neoplasm↗
PubMed1991

[Immunophenotype of lymphocytes of patients with malignant melanoma and its dynamics during immunotherapy with interleukin-2].

A Mab set was used to study immunological phenotype of lymphocytes of five patients bearing stage IV malignant melanoma and its changes developing in the course of interleukin-2 (Euro cetus) immunotherapy. Patients were shown to have lowered counts of T cells (mainly due to T-helper/inducers), B cells and lymphocytes expressing adhesion and activation molecules as well as abnormal immunoregulatory cell ratio. Two patients receiving interleukin-2 achieved a response. Follow-up of antigen expression revealed a rise in natural killer and immunoregulatory T lymphocyte levels in the responders whereas activation antigens and B cell levels were increased in all the patients.

Antibodies, Monoclonal↗
PubMed1990

[The diagnosis and treatment of primary malignant tumors of the sternum].

Results of examination and treatment of 24 patients with primary neoplasms of the sternum including chondrosarcoma (18 cases), solitary plasmacytoma (5) and osteogenic sarcoma (1) were analysed. The diagnosis was based mainly on X-ray procedures and was further improved by computed tomography which allowed to precisely evaluate the extent of intrathoracic mass and its relation to adjacent mediastinal structures. Surgery was the main procedure used for the treatment of primary tumors of the sternum. Sixteen patients were operated on, and not a single case showed involvement of the mediastinum. Closure of defect was the major difficulty involved in the surgical treatment. Adequate resection of the sternum followed by autoplasty yielded good results.

Adult↗
PubMedDate not supplied

[Spectral characteristics of EEG during formation a set to illusory length perception (Müller-Lyer illusion)].

A cognitive set to illusory perception of linear relationships was formed in 56 young healthy subjects. After 10 presentations of Müller-Lyer figures, 39 subjects formed the stable set. In 17 subjects the unstable set was formed. The spectral power of the EEG led from different cortical areas was studied at different stages of set formation. Analysis of variance showed that the factors "set stage" and "group" x "set stage" x "hemisphere" exert significant influence on the EEG spectral power in the delta range in the frontal area. In the subjects with stable set, the power of this spectral component increased at the stages of set formation and actualization and returned to its initial values during set extinction. The between-group difference was more expressed in the left hemisphere. In subjects, which formed the stable set, the power of the occipitotemporal alpha rhythm in the reference state was higher than in subjects with the unstable set. In the process of set formation, the dynamics of the alpha spectral component (8-10 Hz) was more expressed in the stable group: its power increased to a greater extent at the stages of set actualization and extinction. In both groups, there were no significant changes in the alpha2 power over the course of the experiment.

Adult↗
PubMedDate not supplied

[Dependence of the verbal set on the cognitive activity context].

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.

Adolescent↗
PubMedDate not supplied

[Relations between two types of the spatial-temporal organization of the human brain potentials during formation and actualization of set to a visual nonverbal stimulus].

The functional state of the brain cortex estimated by the dynamic changes in the global spatio-temporal organization of brain potentials (STOP) was studied at different stages of the cognitive set formed on the basis of the image of two circles of different diameter. Thirty five subjects (predominantly, right-handed) were examined. The method of quantitative estimation of successive topograms was used for the analysis of the STOP. Two coexisting types of the STOP were described. The relations between them define the functional state of the brain. Quantitative characteristic of these relations is reflected in the value of the coefficient of dynamic variation (CDV). Group of subjects with the stable and unstable set had significantly different values of CDV during the experiment. These groups of subjects also had different topographic characteristics of the CDV.

Adult↗
PubMedDate not supplied

[System changes in the cortical electrical activity and their role in integrative processes in the brain (a synergic approach)].

In the paper, the general theory of systems is applied to a description of the spatio-temporal organization of the summary cortical potentials, synergetic approach is applied for the insight into the functioning of their system changes. This made it possible to consider the human and animal cortical potentials recorded under different experimental conditions from the single viewpoint. The system organization of cortical potentials in multiple derivations was revealed by comparison of momentary topograms (a sequence of momentary values of cortical potentials in all recording points). This technique enables simultaneous estimation of the spatial and temporal characteristics. In the analyzed data array, the independent changes in different types of subsystems of spatial relations between the momentary potential values were found. These subsystems possess both the spatial and temporal characteristics. Parameters of such coexisting dynamic subsystems widely distributed over the cortex present information about the different indices of the system spatio-temporal organization of cortical potentials (STPO), however, only the ratio between the reflected processes is related with the functional features of cortical activity. The brain state and specificity of performance is to a greater extent determined by a reorganization of the topogram relief. The described relatively stable global system relations of cortical potentials during the organism adaptation to the environment principally change under conditions of goal-directed or voluntary activity. In parallel with the increasing role of developing short-term STPO variations, it was found that each stage of performance is characterized by the dominant topogram reliefs. Such reliefs probably present the "order parameters". They can determine spatial characteristics of the new self-organizing in transition periods dynamic systems of cortical potentials, which are related with the forming new functional states of the cortex. It was demonstrated that the functional possibilities of the brain cortex are determined both the dynamics of topogram reliefs and competing or cooperative interaction of the cortical STPO subsystems. The obtained evidence suggest that in parallel with the regional processes closer related with the projection areas of the brain cortex, a global spatio-temporal organization of cortical activity widely distributed over the cortex forms. The role of this organization of the cortical potentials in the integrative brain activity and expedient human and animal behavior is discussed on the basis of the authors' experimental and literature data.

Animals↗
PubMedDate not supplied

[Dependence of stability of the visual cognitive set on motivation].

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.

Adult↗
PubMedDate not supplied

[The variation of two types of spatiotemporal organization of brain potentials at different stages of a cognitive set based on illusory perception of length (Muller-Layer illusion)].

The spatiotemporal organization of brain potentials (STOP) under conditions of their multichannel recording was studied was studied in 35 young healthy subjects during formation, actualization, and extinction of the cognitive set on the basis of illusory perception of length (Müller-Layer illusion) by means of quantitative comparison of successive electroencephalotopograms (ET). The ET is an array of momentary values of potentials simultaneously recorded in all the derivations. An ET is characterized by a relief and mean level. Time changes in these characteristics determine a certain type of cortical STOP. Two main types of STOP were revealed. The interaction between these two types of STOP depended on the kind of performance of a subject and was ferlected in the coefficient of dynamic variation (CDV) of ETs. The CDVs were significantly different in subjects with stable and unstable forms of the cognitive set; in the latter this value was higher. The spectral characteristics of the EEG and STOP dynamics were compared. Analysis of power stectra revealed the significant intergroup differences in the alpha 1 frequency range both in the EEG and STOP; the power of this frequency range was higher in subjects with the stable set.

Adolescent↗
PubMedDate not supplied

[Role of working memory in forming the cognitive visual set].

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.

Adolescent↗
PubMedDate not supplied

[EEG spectral characteristics at different stages of the unconscious visual set in two motivation conditions].

Multichannel EEG were recorded in young healthy subjects in two series of experiments during formation, actualization, and extinction of the visual unconscious set to the perception of unequal circles under conditions of increased motivation of subjects to the result of their performance. In the first series of experiments, subjects were promised to be rewarded (a small money price) for each correct response (the "general" rise of motivation). In the second series, subjects were promised to be rewarded for correct responses only in cases when one of the circles was larger than the other one (the "directed" rise of motivation). The dynamics of the EEG spectral power derived under these two conditions was compared with similar indices obtained earlier during formation of the same set without any special motivation of subjects (control). In all experimental conditions, before the presentation of the stimuli the EEG power in the alpha range was higher in subjects with the stable set. The dynamics of changes in the alpha power at set stages was principally similar in all conditions. In all the experimental conditions, in subjects with unstable set the EEG power in the delta range was highest at the stage of set actualization. The most pronounced generalized changes in the EEG power in the theta-range during the "general" rise of motivation in subjects with stable and unstable forms of set and greater variability of the reaction time to the probe stimulus suggest that the task performance under these conditions required greater tension than under conditions of the "directed" rise of motivation.

Adolescent↗
PubMedDate not supplied

[Changes in the spatial organization of cortical electrical activity during increasing working memory load].

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.

Adolescent↗
PubMedDate not supplied

[The effect of pre-test verbal instruction on spatial organization of cortical electrical activity].

Analysis of coherence of cortical electric activity performed in 30 healthy subjects revealed changes in the spatial organization of cortical electric activity after listening the instruction, i.e., loading the explicit working memory with a sequence of operations of the cognitive task to be solved in the course of the experiment. Comparison of instructions presenting several cognitive tasks showed that greater load of the working memory is associated with higher coherence of cortical activity, especially, in the parietotemporal and occipital areas.

Brain Mapping↗
PubMedDate not supplied

[EEG coherence during unconscious visual set under conditions of increased motivation of subjects].

Prestimulus EEG was recorded in the state of "operative rest" after the instruction and at the stages of formation, actualization, and extinction of unconscious visual set to perception of unequal circles. Two motivation conditions were used: (1) subjects were promised to be rewarded with a small money price for each correct response (a "general" rise of motivation) and (2) only correct assessments of stimuli of a certain kind were rewarded (a "selective" rise of motivation). In both conditions, additional motivation of subjects to the results of their performance led to an increase in EEG coherence most pronounced in the theta and alpha 1 frequency ranges in the left temporal area of the cortex. During the "general" rise of motivation the EEG coherence (as compared to the control group) was higher in a greater number of derivation pairs than during the "selective" rise. EEG coherence in "motivated" subjects was increased already at the stage of operative rest. Later on, at the set stages, no significant changes were revealed. Thus, the realized set formed by the verbal instruction, which increased motivation of subjects to the results of their performance, produced substantially more prominent changes in coherence of cortical potentials than the unconscious set formed during perception of visual stimuli.

Adolescent↗