Biomedical subjects

V N Dumenko

Publications and source records attributed to V N Dumenko.

62 records · Page 4Linked to original sources

PubMedDate not supplied

[The characteristics of the cortical potentials taking into account the high-frequency components in dogs during their instrumental learning studied using nontraditional analytical methods].

A new method of EEG coding (alternative to classical FFT) was worked up. It allowed to compensate for limitations of FFT and to obtain new information on the shape of EEG curve reflecting peculiarities of oscillations of potentials. Proposed technique of EEG coding seems to be adequate for revealing individual and regional features of EEG and their estimation at different stages of instrumental conditioning. Data obtained using this method confirm the reality of high frequency EEG components of small power. In addition, by the method used the intensification of slow wave EEG components was demonstrated in some cortical regions which could not be revealed by FFT.

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PubMedDate not supplied

[The characteristics of the phase relations between cortical potentials in dogs during the acquisition of motor-food conditioned reflexes].

Coherence-phase characteristics of cortical and bulbus olfactorius (BO) potentials were studied during the lever-pressing alimentary conditioning in dogs. These parameters were considered as the basic ones for forming the interareal functional relations in the process of conditioning. Variety of distributions of phase shifts between potentials in a wide frequency band (1-100, 1-256 Hz) at wakefulness permits to think about the spatial-successive processes participating in organization of the brain electrical activity. Values of phase shifts between cortical potentials were significantly less then those between the cortex and BO. At stable conditioned responses phase shifts between the cortical potentials diminished considerably due to intensification of the spatial synchronization processes while those between the cortex and BO increased to a higher degree.

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PubMedDate not supplied

[The dynamics of the high-frequency components of the brain electrical activity in dogs during cognitive activities].

Dynamics of parameters of low-voltage high-frequency components (HFC; 40 Hz and higher) of electrical activity (EA) of the brain in a broad frequency range (1-256 Hz) was studied in dogs in the process of conditioning using correlation and spectral analysis. Motor skill of pressing the pedal of the food dispenser in response to presentation of sound stimuli was elaborated. Spectra of power, coherence and phase of EA were studied in interstimulus intervals (2-3 minutes) and intervals (1 sec) of EEG reaction to conditioned stimuli preceding the motor response. It follows from the distinctions between the parameters of EA at these states that underlying them mechanisms are different. It is assumed that the dynamics of HFC (40-170 Hz) in interstimulus intervals (intensification of HFC and dominance of small phase shifts) is an expression of cognitive activity (forming of the internal integral image of forthcoming activity). Characteristics of EEG reactions to the conditioned stimuli (increase of phase shifts between potentials) are regarded as a "motor program" which ensure direct realization of multicomponent motor reaction.

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PubMedDate not supplied

[The dynamics of the high-frequency components of brain electrical activity (up to 200 Hz) during learning reflects the functional mosaic structure of the neocortex].

The study was aimed to reveal frequency ranges of correlated changes of power spectral densities of the brain electrical activity (EA) including the high-frequency components (HFC) in dogs (4 animals) by means of factor analysis technique. Spectral densities of EA in different cortical areas and olfactory bulb were factored. Relationships between the structure of the selected factors both by the parts of the total variance determined by them and their frequency loads suggest the regional and individual EA differences. In the process of learning (elaboration of motor skill of pressing the food-dispenser pedal with a forepaw) the factor organization of the EA became substantially more complicated, mainly, in the HFC-range (40-170 Hz). This was manifested in formation of narrower frequency subbands of the HFC each of which being highly loaded (0.7-0.8) by one of the factors. The evidence obtained by means of the FA was completely verified using original version of cluster analysis.

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PubMedDate not supplied

[The high-frequency electroencephalogram: the results and outlook].

At present, the significance of high-frequency (HF) components in brain electrical activity (EA) is widely discussed in literature. In particular, the gamma range of human EEG is considered as one of the indices of cognitive activity. In the paper a review is presented of the author's own data concerning the functional estimation of low-voltage HF components of the neocortical EA recorded in the broad band (1-100, 1-256 Hz) in the course of instrumental conditioning in dogs. Three different techniques of EA analysis were used in the study: 1) fast Fourier transformation (FFT) of EA in a broad band, 2) developed by us alternative method of non-harmonic expansion of the EEG curves taking into account their shape, 3) factor analysis of the EA spectral densities. Combination of these techniques allowed us to obtain some novel evidence indicative of high informativity of the HF fluctuations. Spatial cortical localization of the HF components of the EA is much more expressed in comparison with the traditional 1-30 Hz range. Results of factor analysis suggest functional heterogeneity of the HF band. Obtained data open new ways for researches concerning the phenomena of the functional mosaics in the neocortex as one of fundamental mechanisms in brain activity organization.

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PubMedDate not supplied

[An evaluation of the high-frequency components of the brain's electrical activity by using inhomogeneity indices].

The qualitative techniques are considered of mathematical description of curve inhomogeneity which adequately reveal non-stationary fragments in EEG samples with a pseudorandom process. The introduced inhomogeneity coefficient turned to be a sufficiently adequate indicator of the presence of short-term high-frequency bursts in the electrical activity of dog's brain and a sensitive index for discrimination of quasihomogeneous fragments by the level of "general activation". It is shown that the values of this coefficient reflect the individual features of the brain electrical activity of the animals and its dynamics in the process of alimentary motor conditioning. At the same time, this index is ineffective in revealing the regional differences. A novel approach is developed for signal inhomogeneity description which is based on the traditional harmonic analysis (Fourier transform).

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PubMedDate not supplied

[An analysis of changes in the background electrical activity of the dog neocortex during elaboration of food-getting conditioned reflexes].

Background electrical activity of different areas of the neocortex was studied at interstimuli periods during elaboration of food-procuring (instrumental) conditioned reflexes in dogs. By using the complex of EEG parameters obtained after a correlation-spectral analysis, it was possible to provide differentiated EEG characteristics of such externally similar conditions as rest in a situation of food-procuring and in an indifferent situation. Further, it has been found that the background activity parameters significantly differ in one and the same situation of food-procuring, depending on the functional state (passive rest and activation of attention). The data obtained point to the informative nature of background electrical activity of the neocortex, whose parameters reflect the peculiarities of specific functional conditions.

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PubMedDate not supplied

[Bursts of high-frequency synchronized electrical activity in the neocortex of dogs during food instrumental learning].

The EEG phenomenon was studied of high-frequency bursts (60-70 Hz, 70-80 mcV) in electrical activity of dog's neocortex (EA, 1-200 Hz) in the process of instrumental conditioning. These bursts of high-frequency oscillations appeared at the generalization state of the conditioned reflex during interstimulus intervals at the background of dominant EA of the lower frequency and voltage (10-40 mcV). Application of the developed by us novel strategy of the primary analysis of EA realizations (in particular, inhomogeneity coefficient) enabled estimation of the amplitude-frequency EA inhomogeneity, namely, high-frequency bursts. The regional peculiarities of the high-frequency bursts were revealed by means of the original technique based on the expansion of EA oscillation into a system of half-waves and construction of distribution maps on the basis of their parameters. The presented data verified our earlier findings obtained using other techniques (FFT analysis and factor analysis). These data testify to differential participation of cortical areas (even those which are close to each other within a distance of 3-5 mm) in the spatio-temporal organization of potentials characteristic for a given learning paradigm.

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