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Biomedical subjects

A I Fedotchev

Publications and source records attributed to A I Fedotchev.

At least 19 recordsLinked to original sources
PubMed1990

Stability of resonance EEG reactions to flickering light in humans.

In order to study resonance phenomena in the EEG response to flickering light, 10 subjects were exposed to intermittent photic stimulation with the frequency of flashes linearly changing from 1 to 15 Hz and vice versa. Spectral analysis of occipital electrical activity revealed the occurrence of peaks of spectral density in those frequency components which coincide with the frequency of flashes. Such resonance peaks were observed at individually specific frequencies of stimulation. To assess the stability of the characteristics of the resonance phenomena, a repeated trial with 4-fold higher rate of changing the flash frequency was performed 3 months later. In a repeated trial the resonance phenomena were less pronounced, but were registered at the same frequencies as in the initial trial, showing significant test-retest reliability. The data obtained are interpreted in terms of provoking the activity of multiple brain oscillators having a narrow tuning to individually specific frequencies of photic stimulation by flickering light with the changing frequency of flashes.

Adult↗
PubMed1988

[Effect of intermittent photostimulation of varying frequency on the formation of trace processes and spectral components in the human EEG].

The EEG of occipital areas was recorded in adult healthy male subjects on presentation of haphazardly alternating intermittent light stimuli with frequencies varying from 15 to 5 Hz and from 15 to 25 Hz every 5 sec. Two groups were distinguished in respect to a greater or lesser domineering of the main frequency band of the range. Dynamic spectral analysis revealed obvious shifts of the EEG spectral composition in respect to the background under the effect of the stimulation, an enhancement of different bands of the range in light flickering, and the suppression of the EEG trace responses to the time in the EEG range coinciding in frequency with the frequency range of the photostimulation. The above changes were mainly characteristic of the 2nd group of subjects and mostly of the left hemisphere of the brain.

Adult↗
PubMedDate not supplied

Electrical activity of the cortex and reaction times to auditory signals and light stimuli.

We investigated the electrical activity of the occipital, sensorimotor, and frontal zones in the right and left hemispheres of the cerebral cortex and times for bimanual motor response in healthy adult experimental subjects between the ages of 15 and 25 receiving photostimulation by means of pulse trains with frequencies increasing from 15 to 25 Hz and pulse trains with frequencies decreasing from 15 to 5 Hz. We observed nonspecific physiological reactions in the organism regardless of the type of photostimulation presented and also observed specific reactions dictated by the parameters of the light stimulus acting upon the brain. It was demonstrated that the action of the light was most effective when the frequency of the stimuli was gradually increased. The expressiveness of the alpha-band of oscillations in the electrical brain activity increased in this case, and the asymmetry of the bimanual motor responses changed significantly. A definite connection was noted between the physiological reactions of the experimental subjects and their subjective states.

Acoustic Stimulation↗
PubMedDate not supplied

[The rhythmic structure of the human EEG: the current state and trends of the research].

During the past decade, spectral analysis has become indispensable instrument for different kinds of EEG processing. With the development of dedicated computer system, investigation of shifts in human EEG rhythm under various conditions has improved considerably. However, it is difficult to make general conclusions from this line of research, since a large number of studies are carried out using the ambiguous experimental approaches and different methods. Present paper aims to evaluate a modern state of the art in the field of human EEG rhythmical structure investigation. The results from recent relevant articles are briefly reviewed according to the universal scheme (EEG rhythm--experimental condition--observed effect). Due to such presentation, the obtained results have been summarized and some tendencies of modern investigations have been revealed. The extension of studied frequency range of rhythmical EEG components to both high (> 35 Hz) and low (< 1 Hz) frequencies, the shift to a more detailed spectral structure analysis simultaneously with ignoring the fixed boundaries of traditional EEG rhythms, the growing attempts to reveal EEG rhythmical structure correlates of cognitive activity, and a wide utilization of dynamic approaches for the analysis of brain electrical activity are discussed in some detail. The observed data are indicate of high functional significance and perspectives of human EEG rhythmical structure investigation.

Brain↗
PubMedDate not supplied

[Dynamic processes in the human EEG].

The possible mechanisms which determine the temporal dynamics of discrete narrow-band spectral components of human EEG recorded by a single electrode in the state of rest were analyzed. The dynamics of short-segment spectra was observed by application of Fast Fourier Transform (FFT) to 5-s EEG epochs successively shifted by 0.32 s. For each subject the matrices were formed and presented in a graphic mode. Matrix rows represented the number of points in each short-segment spectrum, and the columns represented the number of short-segment spectra. The columns reflect the amplitude dynamics of a given frequency, and power transition between the columns reflects the frequency dynamics. The most common type of the amplitude dynamics consisted in short (2-8 s) periods of stable activity of the discrete spectral components replaced by symmetrical bifurcation or confluence of spectral peaks. The obtained results suggest by the presence of both additive and multiplicative mechanisms of oscillatory interactions in the EEG. More detailed analysis of the amplitude-modulated EEG processes is provided by application of some additive features of the FFT to both EEG and computer-simulated signals.

Adult↗
PubMedDate not supplied

[Photoinduced resonance phenomena in the human electroencephalogram as a function of frequency, intensity, and duration of stimulation].

The features of resonance phenomena in high-resolution EEG structure were analyzed for two intensities and three values of duration of exposure to 20 constant frequencies of intermittent photic stimulation in a range of 1-20 Hz with 1 Hz steps. It was shown that with a 6 s step duration, an irregular activation of multiple spectral EEG components for both light intensities occurs. With longer durations (12 and 18 s) of fixed-frequency stimulation, the EEG reactions are of resonance nature. Low-intensity flashes cause only the resonance activation of the intrinsic oscillator in the range of dominant alpha-EEG frequency. During a more intensive stimulation, the resonance EEG phenomena are observed for the whole range of stimulation frequencies. The interval of 6-12 s is supposed to be the relaxation period for a system of brain electrical activity generation. After this time, the low-intensity stimuli cause the adaptation of the system to light, whereas more intensive flashes cause more pronounced resonance EEG phenomena and physiological effects.

Electroencephalography↗
PubMedDate not supplied

[Resonance phenomena to rhythmic light stimulation with various intensity and frequency in human EEG].

The photoinduced resonance EEG response in the occipital area (O1 and O2) of right-handed men during 12-s intermittent photic stimulation was studied as a function of flash frequency (6, 10, or 16 Hz) and intensity (5 levels from 0.05 to 0.7 J). The EEG power in the narrow band coinciding with stimulation frequency was FFT-extracted in 3-s intervals before, during, and after each stimulation. It was found that increase in flash intensity was accompanied by an enhancement of the resonance EEG response and decrease in time of reaching its maximal value. These changes were to a greater extent characteristic for the right hemisphere. The low-intensity stimulation induced more pronounced resonance effects in the left hemisphere, whereas the high-intensity flashes to a greater extent involved the right hemisphere. The asymmetry of the EEG response to stimulation of the middle intensity was slight, and the time of reaching the maximal level of the resonance activation was about 6-8 s. A relatively high level of the resonance EEG response was observed during stimulation with the frequency of 10 Hz, even in case of its minimal intensity. The most pronounced resonance EEG response was induced in the right occipital area by the high-intensity 16-Hz stimulation. The enhanced sensitivity of the right hemisphere to intensity of flashes is interpreted as an indication of interhemispheric differences in nonspecific adaptive mechanisms of the brain.

Brain↗
PubMedDate not supplied

[Temporal changes in conscious and unconscious trace phenomena in six to seven-year-old children].

Development in time of unconscious trace reactions as well as a change in the time of reproduction of verbal material in natural conditions was studied by the conditioned reflex to time method on 107 school children aged from six to seven years and on 35 subjects of the same age from a kindergarten. It has been found that in schoolchildren the transfer of trace reactions to long-term storage is completed faster, and their voluntary acts in the course of conscious reproduction of an interstimuli intervals are more adequate than in the kindergarten children of the same age. The trace phenomena formed in natural conditions and in the laboratory experiment develop in time in a similar way. The change in time of conscious trace phenomena is of a more complex nature than of the unconscious phenomena. The practical significance of the data obtained is noted.

Brain↗
PubMedDate not supplied

[Biofeedback training and human functional state control].

Biofeedback (BFB) training paradigm has outstanding place among various approaches to non-phrarmacological human functional state correction. Being an universal way for voluntary self-regulation of physiological functions, it is characterized by efficacy, accessibility and absence of side effects. However, the lack of fundamental knowledge about the BFB mechanisms leads to existence of numerous difficulties and problems that seriously limit the BFB possibilities. Most difficulties seem to concern the problem of adequate choice of BFB type or parameter being voluntary controlled via feedback signals. Some ways to solve this problem are drown on the base of general systems theory. It is shown that BFB procedures could be especially effective in conditions of close interaction between the BFB mechanisms and the central regulatory mechanisms. Such interaction could be reacheb by utilization of certain characteristics of brain electrical activity reflected in the electroencephalogram (EEG). The most perspective seems to be the utilization of discrete narrow band EEG spectral components, individual resonance EEG oscillators or some correlates of human EEG amplitude modulation processes.

Biofeedback, Psychology↗
PubMedDate not supplied

[The dynamic and regional characteristics of the high-resolution EEG structure in voluntary activity].

For revealing the dynamics of interrelations between EEG components having stable tuning to individually determined frequencies a dynamical high resolution EEG structure analysis was used. There were three successive experimental stages: rest, motor reproduction of time interval and tapping. Significant increase of EEG components intercorrelations for the right frontal area, minimal number of significant relationships between EEG and movement temporal characteristics, and the occurrence of hemispheric asymmetry in the number of EEG-movement correlations were observed for time reproduction task. This task specifics and the possibilities of used approach for precise functional states differentiation are discussed.

Adult↗