The characteristics of the temporospatial organization of cerebral cortical potentials at different levels of genetically determined emotionality were analyzed by constructing topograms of instantaneous EEG levels in the inbred rat strains MR and MNRA. Two parameters were calculated for each topogram: the total level and the similarity coefficient. Power spectra were calculated for the values and these were found to change in an oscillatory manner. Interstrain differences were found in the correlated changes in total levels and similarity coefficients, in the durations of changes in the total level, which were more marked than those of similarity coefficients, and the nature of interhemisphere asymmetry. In MR rats, the power spectra of both measures showed significant peaks with modes at 2.0, 6.5, and 9.0 Hz. In MNRA rats, peaks in the spectra of these measures both coincided (2.0 Hz) and differed (7.0 Hz in the spectrum of the total level and 3.0, 4.5, and 6.0 Hz in the spectrum of the similarity coefficient). These data suggest different types of functioning of the reticulothalamocortical and hippocampocortical systems in rats of these strains.
This report concerns the important question of the specificity of the organization of the different stages of formation of a conditioned reflex, considered at the level of membrane-synaptic modifications, which are compared with changes in the spatial organization of slow cortical potentials. A defined sequence of involvement of cellular mechanisms is demonstrated during learning, which may be responsible for various features of the spatial organization of slow cortical potentials. Changes in cellular excitability in cortical neurons are probably connected with oscillations in the overall level of instantaneous topograms and, thus, with the general level of spatial synchronization; the involvement of excitatory and inhibitory synaptic connections (with efficiencies corresponding to different stages in the reflex) may determine the formation of the relief seen in topograms. Parameters at both levels depend on the effects of the hypothalamus on the cortex.
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