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Biomedical subjects

I E Kanunikov

Publications and source records attributed to I E Kanunikov.

At least 19 recordsLinked to original sources
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↗
PubMed2006

[Reflection of cortical activation pattern in the human EEG phase structure].

Investigation was fulfilled on healthy subjects (22) and on outpatients (62). The EEG by the standard scheme as recorded at resting with open and closed eyes and under different functional loads. These records were processed in accordance with the EEC phase structure with the aid of computer animation technology. The main idea of the phase structure technology consists in rejection of one supporting lead. Time shifts were measured only between two neighbouring electrodes, so that the oscillations under comparison were always highly coherent. Time errors were evaluated according to crosscorrelation function maximum shift. The differences between high- and low-frequency EEG rhythms were shown to be only quantitative from the phase structure viewpoint. Qualitatively, the rhythm properties were equal and came to slow (second) phase structure oscillations. Low frequency activity compared to high frequency one was characterized by greater phase shifts from electrode to electrode. Phase shifts of potentials are forming the structure which, as a whole, is very similar in different people and is reproduced in different states. Initial EEG waves appearance is statistical linked with main sensory projections: visual (occiput), auditory (temples) and somatic (parietal region) with addition of frontal region. Redistribution of phase leadership in favor of occipital pole and to both temporal regions when eyes are open is described. It is apparently dependent on the sensory surge level from thalamus to a given cortex region. Phase gradient direction seems to reflect the cortex current density gradient which is parallel to surface. It can be used for localization of compact sources lying near to cortex.

Adolescent↗
PubMed2004

[Individual dynamics of the EEG running wave under various conditions of activity].

In 25 healthy subjects at resting with their eyes closed and open, a current phase structure of the EEG was measured, i.e. a trajectory and velocity of oscillation spreading over the head surface in temporal-occipital area. Visual computer multiplication revealed stable individual specifics of the EEG "running wave" dynamics which were then confirmed independently proceeding from the statistical significance criteria. Some subjects had characteristic transversal modulations of the EEG waves (from the left fo the right and vice versa), other subjects manifested longitudinal modulations along the diagonal from the cortex left anterior areas to the right posterior those (in some of them) or along the same diagonal in the opposite direction (in others). When opening the eyes, the character of the EEG "running wave" undergoes dramatic changes. Among other parameters, a growth of the trajectory share occurs in occipital area along with acceleration of the "running wave" spreading on all other trajectories. Both effects are bound to each other and the sharper dynamics is specific for subjects characterised as sympathotonic those as compared with para-sympathotonic.

Brain↗
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

[Evaluation of EEG(D2) and CNV correlation dimension in various forms of visual attention in human].

In 16 healthy subjects, the EEG and the CNV (contingent negative variation) correlation dimension was studied during preparing to pay attention to one of three attention tasks: the situations "What", "Where" and "What and where". Two easily discernible symbols (squares and circles) were used as stimuli. The findings show that, irrespective of the attention form, the correlation dimension of the EEG, the CNV amplitude, and the evoked potential's N1-P3 component amplitude had maximal values in the temporal leads. The temporal visual system seems to play a domineering part in the tasks of spatial and non-spatial attention to stimuli in humans.

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↗
PubMed2001

[Correlation of spatial EEG synchronization with verbal-logical and visual-spatial abilities in humans].

The EEG was recorded from five monopolar leads: a spontaneous one as well as the EEG during verbal-logical or visual-spatial tests, in humans. The subjects with prevailing visual-spatial abilities had a spontaneous EEG with a low intercorrelation between the hemispheres and a higher level of the EEG synchronisation in parietal-occipital areas as compared with the frontal those, whereas subjects with prevailing verbal abilities had an inverse correlation of the above EEG parameters. The parameters' interrelationships in subjects' spontaneous EEG seem to reflect an individual and specific character of cerebral neurodynamics suggesting a negative correlation between the verbal-logical and visual-spatial abilities in humans.

Adult↗
PubMed2000

[Reflection of the type and successfulness of the cognitive activity in the human EEG: application of nonlinear methods in psychophysiology].

The information processing by the human brain was studied in two types of cognitive activity: solving a visual-spatial task and a verbal task. One of the Wechsler tests represented a visual-spatial task, whereas a speed-reading was used as a verbal task. A correlation dimension calculated from the EEG time series, was shown to depend on individual capabilities. Subjects with a higher correlation dimension in frontal brain areas executed more successfully the spatial task.

Adult↗
PubMed1999

[The indices of EEG spatial synchronization in normal 10- to 12-year-old schoolchildren and in learning difficulties].

10-12-year-old schoolchildren were divided into three groups: a normal one, a group with psychological problems, and a third one with medical problems. The EEG was recorded at resting and while reading a text. An obviously higher global spatial synchronisation was found in the normal group as compared with the "medical" one. In the "psychological" group, a diffuse hyperresponsiveness was found in the transition state from resting to activity. The above differences seem to be due to a morpho-functional immaturity and a functional insufficiency of two different portions of the brain ascending activating system. Evidently the "medical" group children have an immaturity of the bulbar and midbrain reticular formation, whereas the "psychological" group children have, probably, an immature diencephalic activating system (the thalamus).

Adaptation, Psychological↗
PubMed1998

[Dependence of human EEG spatial synchronization on the geomagnetic activity on the day of experiment].

Spontaneous EEG was registered under different activity conditions in 26 volunteers. The EEG synchronisation parameters were compared with the geomagnetic and solar activity on the day of experiment. A positive correlation of the EEG data with the geomagnetic activity was revealed, being most obvious in the frontal and central areas. A negative correlation between some local EEG synchronisation parameters and different indices of the solar activity, was also revealed. The degree of synchronisation of the spontaneous EEG seems to reflect sensitivity of the human nervous system to the Earth's magnetic field. A stressor response to strong short-term disturbances in the geomagnetic field reveals itself in the form of enhancement of the EEG global synchronisation. A sedative effect of slow magnetic oscillations is locally revealed in the parameters of the EEG synchronisation within the left hemisphere as well as the interhemisphere synchronisation.

Adolescent↗
PubMed1997

[The effect of sex on the spatial synchronization of the EEG].

The data obtained shows that women are characterised by a significantly larger interindividual variations of the EEG synchronizing than men (except the synchronizing in the left hemisphere). The findings are supposed to be due to a higher level of unspecific cortical activation in men.

Adolescent↗
PubMed1993

[The form of the spontaneous EEG waves under different conditions of mental activity].

Value of the average level of asymmetry of the EEG waves' fronts (ALA) was shown to decrease in posterior leads and increase in anterior leads during the transition from the rest to mental activity. An inter-hemisphere asymmetry of the ALA was found, the asymmetry having a similar direction for all the pairs of symmetrical leads. Two independent factors are supposed to affect the ALA: the level of the cortex activation and the specifics of information processing by the given hemisphere.

Adolescent↗
PubMed1991

[The mean level of EEG wave asymmetry as a possible correlate of the property of lability of the cerebral hemispheres].

The human nervous system's lability was studied with the aid of critic fusion frequency (CFF). The CFF was compared with the mean level of asymmetry of the EEG waves' fronts (MLA). The CFF was shown to be a relatively stable individual parameter whose value depended on the value of difference between occipital and frontal areas' MLA and those in the lower frontal areas.

Adult↗
PubMed1991

[The reflection of functional differences between the hemispheres in the form of the EEG waves].

The EEG was recorded in 3 symmetrical sites of the human brain with subsequent calculation of the parameter of mean level of asymmetry (MLA) in the EEG wave fronts. The MLAs were shown to change after functional loads of visual-spatial and verbal-logical types. The MLA seems to be an informative parameter of qualitative specifics of neural processes in the left and right hemispheres.

Adolescent↗
PubMed1984

[The problem of the functional meaning of EEG indices and the principle of dominance].

CNV was studied from the Ukhtomsky dominant theory standpoint in subjects performing four different types of tasks. The CNV appears to have a complicated spatial-temporal organization and can be satisfactorily described with the aid of four relatively independent components differing from each other in their location, time of development and sensitivity to varying of monitored variables.

Contingent Negative Variation↗