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Biomedical subjects

V T Shuvaev

Publications and source records attributed to V T Shuvaev.

At least 19 recordsLinked to original sources
PubMed2006

Cross-interval histograms for analysis of brain electrical activity.

A method for constructing cross-interval histograms for time-localized EEG fragments of particular types is described. The basic principles of the method are presented. Examples of cross-interval histograms constructed for EEG extrema and their derivatives are presented. Cross-interval histograms were shown to include peaks, troughs, and other features. Cross-interval histogram and cross-correlation histograms are compared. The method yields qualitatively new data on interactions between changes in biopotentials in different areas of the brain and allows rapid processes to be studied.

Brain↗
PubMed2006

[Characteristics of the parietal cortex activation in humans during different attention tasks].

The cortical activation was estimated by the event-related potential (ERPs) methods during selection tasks of lateralized visual stimuli requiring different forms of attention: 1) form of stimuli, 2) stimuli position, 3) combined attention of form and position. The ERPs were recorded in 15 young healthy adults in 6 leads P3, P4, T3, T4, T5, T6, and endogenous ERPs components: CNV (contingent negative variation), N1, P3 and the complex [N1-P3]. Differences between the ERPs at "attended" and "non-attended" stimuli were considered as indices of selection attention of particular feature of visual stimuli. Such indices of form and position were revealed selectivity in parietal leads. The most eminent ERPs components, the pronounced activation gradient during increase of attention demands were revealed in parietal regions (vs. temporal ones). In our opinion, parietal cortex has a high priority in selection attention system.

Adolescent↗
PubMed2006

[Interhemisphere differences of extrastriate cortical activation during attention and selection of lateralized visual stimuli in humans].

The cortical activation was estimated by event-related potentials (ERPs) methods during selection tasks of lateralized visual stimuli in right and left hemi-fields requiring different forms of attention: 1. Attention of a stimuli form, 2. Attention of a stimuli position, 3. Combined attention of form and position. ERPs were recorded in 15 young healthy adults in 6 leads: P3, P4, T3, T4, T5, T6 and endogenous ERPs components: CNV (contingent negative variation), N1, P3 and complex [N1--P3]. The differences between ERPs at contra- and ipsilateral stimuli in the right and left hemispheres were considered as indices of asymmetry. The asymmetry was revealed in right hemisphere in all kinds of attention forms. The level (amplitude) of right-side asymmetry was depended on the level of attention: The significant relation between the right-side asymmetry and subjects' reaction time was also revealed. It is proposed that such an asymmetry is the evidence of better spatial differentiation of visual stimuli in right hemisphere in humans.

Adolescent↗
PubMed2005

Effects of selective visual attention in the parietal and temporal areas of the human cortex using evoked potential data.

Studies of 11 young subjects addressed the analysis of evoked potentials in the parietal and temporal areas to sequential presentation of visual symbols on the left and right sides; symbols were squares and circles and were observed passively and in conditions of selective attention to target stimuli presented to the subjects in random order and requiring rapid and precise motor responses. Comparison of monopolar evoked potentials in leads P3, P4, T3, T4, T5, and T6 with bipolar potentials in leads P3-T3, P3-T5, P4-T4, and P4-T6 in conditions of passive and selective attention showed that voluntary attention was accompanied by significant rearrangements in evoked activity in the parietal and temporal areas. This was evident as: 1) an increase in correlations between evoked potentials in the parietal and temporal areas; 2) stabilization of monopolar evoked potentials over time, i.e., increases in the correlations of sequential evoked potentials, in both associative visual areas; 3) stabilization of bipolar parietal-temporal evoked potentials in terms of increases in their sequential correlations. It is suggested that selective attention facilitates linked activity of the two associative areas, which is needed for performance of visual selection.

Adolescent↗
PubMed2004

Genetic determination of neurophysiological mechanisms of cortical-subcortical integration of bioelectrical brain activity.

The contribution of genetic factors to the formation of the neurophysiological mechanisms of cortical-subcortical integration was studied in 12 pairs of monozygotic and five pairs of dizygotic twins (aged 18-25 years). Intrapair similarity of the nature of spatial interactions between bioelectrical activity in the cerebral cortex, assessed from different combinations of statistical interactions of EEG from 16 monopolar recordings, was assessed in each pair of twins (and among 544 non-related pairs of subjects in both groups). The results suggest a high level of general population invariance and relatively small inherited and phenotypic variability in the morphofunctional systems making up the major neurophysiological mechanisms of brain integration as a whole. The ontogenetic formation of stem and subcortical regulatory structures, which have a leading role in the systems combination of different parts of the brain into a single formation, appears to occur in all individuals by the same principle, as disturbance can apparently affect the fundamental monomorphic features of the species. In turn, we might expect to find large interindividual variability in the establishment of interregional connections of the neocortex, the role of inherited and environmental factors being different in the processes forming long and relatively short intercortical interactions.

Action Potentials↗
PubMed2003

Assessment of the state of activation of the cortical zones in humans during visual attention and selection.

The state of cortical activation during visual symbol shape and position selection tasks was assessed in humans in terms of the magnitude of prestimulus negativity (contingent negative variation, CNV) and the amplitude of the N1-P3 complex in evoked potentials (EP). Evoked potentials in the frontal parietal, occipital, and temporal leads were recorded in 18 young healthy subjects in two sets of experimental conditions: in a screened chamber and in an "open field" beside the experimenter, who communicated the results to the subjects and guided them towards quicker and more precise responses to the target stimuli. The maximum magnitudes of CNV and evoked potentials during selective attention were seen in the parietal areas, and additional increases of activation indexes were observed in the "open field," where subjects' motivation was enhanced. The state of readiness (CNV) was an informative measure of cortical activation, as it determined the parameters of subsequent evoked potentials; the more marked the readiness, themore marked and stable were EP. Comparison of the situations of passive observation and selective reactions to stimuli revealed a reciprocal relationship between CNV in these conditions: the greater the magnitude of CNV in "passive" conditions, the smaller the difference between CNV in "passive" conditions and during selective attention and vice versa. We termed this "additivity of involuntary and voluntary attention." The fact that activation indexes were greatest in the parietal areas suggests that the occipital-parietal system is dominant in visual selection tasks in humans.

Attention↗
PubMed2003

[Manifestations of selective visual attention in human parietal and temporal cortex according to evoked potentials].

The event-related potentials (ERPs) in visual discrimination task in parietal and temporal cortical areas were recorded in 11 young adults during passive observation (involuntary attention) and target selection (voluntary attention). The voluntary selective attention resulted in: 1) increased ERP correlation between the parietal; and temporal cortical areas; 2) increased correlation of sequential ERPs in monopolar leads (P3, P4, T3, T4, T5, T6); and 3) increased correlation of sequential ERPs in bipolar leads (P3-T3, P3-T5, P4-T4, P4-T6). The findings suggest that voluntary attention maintains a concordant activity of the parietal and temporal cortical areas in execution of visual selection tasks.

Adolescent↗
PubMed2002

[Activation of the human cortex during visual attention and selection].

Cortical activation in visual discrimination tasks was estimated by measurement of the CNV (contingent negative variation) and N1-P3 components of visual ERPs in frontal, parietal, occipital and temporal leads recorded in 18 young healthy adults. In all investigated tasks, the maximal values of CNV and ERPa were observed in parietal regions. The estimation of cortical readiness state (CNV) is quite a useful procedure in the attention tasks because amplitude and stability of ERPs depend on preceding cortical excitability. The prevalence of parietal activation in visual attention tasks may be considered as the dominance of occipito-parietal way (stream) in human visual attention system.

Adult↗
PubMed2002

[Genetic determination of the neurophysiological mechanisms of the cortico-subcortical integration of bioelectrical activity of the brain].

Contribution of genetical factors to neurophysiological mechanisms of cortico-subcortical integration was investigated in 12 pairs of the monozygotic and 5 pairs of dizygotic twins (aged from 18 to 25). In each pair of twins as well as in all 544 unrelated pairs of subjects from both groups, interpairs similarity of the character of the spatial interaction of bioelectrical activity of the neocortex for different combinations of statistical correlations of EEG (from 16 monopolar electrodes) was estimated. The data obtained allow to suggest a higher common population invariance and a relatively small hereditary and phenotypic variability of morphofunctional systems, which underlie neurophysiological mechanisms of the brain integration in general. Apparently, the formation of the brain stem and subcortical regulatory structures in the ontogenesis, the structures that play the main role in the realization of system combination of different parts of the brain into united formation, occurs to all individuals according to a single principle since its disturbance can probably affect the fundamental monomorphal features of the species. In turn, one can expect a great interindividual variability of establishing of the intraregional connections of neocortex, the role of genetic and environmental factors in the formation of short and relatively long interactions being complex.

Adolescent↗
PubMed1996

[Functional transformations of the human brain during emotional self-regulation with biofeedback].

By means of a special technique, mobilising of a subject's selective attention upon the dynamics of the subjective sphere states, was reached. An involved biofeedback was positively reinforced by avoidance of an expected electric stimulus. The subjects revealed occurrence of an adaptive correction of their general behaviour. The EEG computer analysis manifested a specifics of structural-functional maintenance of different states evoked in the training process.

Adult↗
PubMed1995

[The corticostriatal mechanisms of behavior].

Experiments in dogs, cats and monkeys revealed that, along with the diffuse principle of afferent terminal arrangement within the striatum, there exist some features of terminal organisation by the anterior-posterior and medio-lateral gradients. The data obtained suggest that the prefrontal cortex and the caudate nucleus head maintain programming of intentions and the evaluation of performed actions.

2-Aminoadipic Acid↗
PubMed1995

[Neurophysiological mechanisms of the cortical-subcortical interrelationships in the organization of behavior].

Specific intersystem relationships seem to exist characterising interrelationships among neurons within pools of which plasticity of a single neuron is able to maintain integration processes of the whole system. The neurons under study seem to become united into various functional blocks during different phases of conditioned behaviour which determines a formation of a dominant condition of the centres and vectors of a specific behavioural action in a given situation and at a given time.

Animals↗
PubMed1994

[The structure of the neuronal activity of the caudate nucleus in monkeys making a decision and realizing the motor program in different variants of a task of delayed spatial choice].

Spatial-selective neurons were found in the monkey caudate nucleus, the neurons being divided into two groups: one of them reflects the location of conditioned signals, the other--the direction of future motor response. The decision-making process is reflected in the unit activity in two aspects: as formation or choice of a concrete motor program, and as a transitory moment from instructive to executive phase of the behaviour.

Animals↗