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Biomedical subjects

E A Kostandov

Publications and source records attributed to E A Kostandov.

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

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↗
PubMed2006

[Significance of the cognitive context in formation of unconscious visual sets].

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

Brain↗
PubMed2001

[A cognitive set and top-down processes in the functional organization of visual recognition].

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

Animals↗
PubMed1995

[The characteristics of the cognitive defect in patients with different variants of late paranoia].

Evoked cortical activity in response to acoustic stimuli (oddball paradigm) was studied in patients with different paranoid disorders. The analysis covered the N150 negative wave and positive complex P300. In patients with paranoid schizophrenia and paranoid form of involutional psychosis cortical responses to the stimuli and cortex effects were not recorded. Such cognitive deficiency is believed to be typical for schizophrenia.

Aged↗
PubMed1994

[The psychophysiological criteria for assessing the excitable type of psychopathy].

In the excitable psychopaths and persons with some psychopathic traits (Leonard's "accentuated personality") the study was made of a cognitive function of discriminating microintervals and event-related potentials to visual stimuli. A qualitative difference in the accomplishment of the cognitive task between the two groups was found. Disturbances of the cognitive function, learning deficiency and reduction of the P300 wave provide grounds for referring this ""antisocial personality disorder" to pathology of the limbic system of the brain.

Adult↗
PubMed1993

[Disorders in the mechanism of information selection in schizophrenic patients].

Two groups of schizophrenics with negative and positive syndromes were studied by registering cortical evoked potentials in response to acoustic stimuli of different meaning (odd-ball paradigm). Disfunction of selective attention is related to the impaired ability to differentiate relevant and irrelevant information. Disturbances of information selection were more pronounced in the patients with paranoid schizophrenia.

Acoustic Stimulation↗
PubMed1991

[Relation between cognitive activity of excitable psychopathic personalities and the pattern of reinforcement].

Excitable psychopathic personalities manifest qualitative and quantitative disorders of cognitive activity directly unrelated to emotional reactions. If the result of the activity is estimated by some other person with the aid of positive and negative reinforcement stimuli, deficit of the training is marked to a much greater degree than in cases where the excitable personality itself draws, on the basis of information available in the feedback stimulus, the conclusion whether its decision was right or erroneous.

Adult↗
PubMed1990

[The negative consequences of the joint session of the 2 Academies in Soviet biological psychiatry].

The liquidation of the scientific school in the brain pathology based by distinguished psychiatrist A. S. Shmar'ian, serves as an example of the negative role in the development of Soviet psychiatry played by the joint session of the USSR Acad. Sci. and Acad. Med. Sci. dedicated to the problems of I. P. Pavlov's physiological theory (June-July, 1950), and the joint session of the Presidium of the USSR Acad. Med. Sci. and the National Society of Neurologists and Psychiatrists (October, 1951). The absurd fight against dissidence in science harmed the studies in neuropsychiatry, where Soviet school had been among the most advanced world schools.

Academies and Institutes↗
PubMed1990

[Differences in the effect of diazepam on realized and non-realized conditioned emotional reactions].

Evoked cortical potentials in response to conditioned visual stimuli were recorded in excitable psychopathic personalities in the course of formation and reproduction of temporary relations with a realized or non-realized emotional word. Diazepam (10 mg intramuscularly) suppresses cortical reaction worked out previously with the aid of a realized emotional word and fails to produce and action if that word was non-realized. The fact of the lack of the diazepam effect on conditioned emotional reactions formed at the non-realized level should be taken into consideration in the treatment of patients with disturbances in the emotional sphere.

Adult↗
PubMed1987

[Disorder of selective attention in patients with late-manifesting schizophrenia with a syndrome of involutional paranoia].

Selective attention was studied by registering cortical evoked potentials to acoustic stimuli in mental patients and mentally healthy subjects of old age. Disorder of selective attention in the patients was manifested in an impaired ability of the higher portions of the central nervous system to differentiate between essential and non-essential external stimuli as well as in a weakened inhibition of irrelevant information.

Aged↗
PubMed1986

The influence of subliminal emotional words on functional hemispheric asymmetry.

The P300 component of the evoked potential was recorded over both hemispheres in order to study interhemispheric differences in the process of perception of subliminal verbal stimuli. The stimuli--subliminal words, neutral and emotional--were presented at random to the left or right visual fields. In response to an unrecognized emotional word, the amplitude of P300 wave increased diffusely over both hemispheres as compared to that to a neutral word, with no changes in interhemispheric differences. The interhemispheric difference changed considerably in the presence of an 'unaccountable' emotion caused by a subliminal word. This suggests a unilateral activation of the right hemisphere and a predominant role of this hemisphere in the cortical organization of the unconscious function 'unaccountable' emotion.

Adolescent↗