[Spectral correlation analysis of the potentials of the neocortex and certain subcortical structures during low-frequency electrical stimulation of nonspecific thalamic nuclei]. / Spektral 'no-korreliatsionnyi analiz potentsialov neokorteksa i nekotorykh podkorkovykh struktur pri nizkochastotnom élektricheskom razdrazhenii nespetsificheskikh iader talamusa.

The spectral-correlation analysis of biopotentials in the cortex and some other brain structures (the anteroventral thalamic nucleus, dorsal hippocampus, lateral geniculate body, mid-brain reticular formation), in chronic experiments on alert rabbits, revealed that during electrical stimulation of thalamic mid-line nuclei within the ranges of 1-3, 4-7 and 8-10 c/s, there occured a rearrangement of the EEG frequencies; a dominant, narrow-band peak at the stimulation frequency, appeared. The coherence of the biopotentials of different cortical areas, of the cortex and subcortical formations increased during the stimulation at the frequency of the stimulation, reaching maximum values between the potentials of the visual and sensorimotor cortical areas.

[Correlation between bioelectrical processes of the cortex, thalamus, midbrain reticular formation during formation of a defensive conditioned reflex in rabbits]. / Sootnoshenie mezhdu bioélektricheskimi protsessami kory, talamusa i retikuliarnoi formatsii srednego mozga pri formirovanii oboronitel'nogo uslovnogo refleksa u krolika.

EEG power spectra of the sensorimotor area of the neocortex, the dorsal hippocampus, midbrain reticular formation and anteroventral thalamic nucleus, as well as corresponding coherence functions and phase spectra, undergo changes during formation and performance of defensive conditioned reflex in rabbit. The conclusion is draen that in the process of conditioning a morphofunctional system of brain structures is established including the above mentioned formations. Their functional integration occurs on the basis of theta-rhythm. The execution of a conditioned act requires isorhythmicity of electrical processes within the theta-range in the studied structures and an adequate level of their excitability, which is manifested in the dominance of 6,0 c/s frequency.

[Spectral characteristics of the bioelectrical activity of the cerebral cortex upon electric stimulation of subcortical structures]. / Spektral'nye kharakteristiki bioélektricheskoi aktivnosti kory bol'shikh polusharii pri élektricheskoi stimuliatsii podkorkovykh obrazovanii

A spectral-correlation analysis of electrical activity of the rabbit cerebral cortex was made with the use of Dnieper computer, after electrical stimulation (100-250 c/s) of the midbrain reticular formation, the thalamic nonspecific formations (midline nuclei) and different nuclei of the posterior part of the hypothalamic area (ventromedial and posterior hypothalamic nuclei and the lateral field). The background spectrograms were characterized by a high variability; their frequencies ranged from 0,5 to 12 c/s. Under the influence of the electrical stimulation of the indicated formations, a well-pronounced, dominating peak appeared in the spectrograms of the cortical EEG, in the band from 4 to 7 c/s, and the similarity of biopotentials in this rhythm increased. The experimental data show that enhancement of spatial synchronization of the cortical biopotentials under conditions of electrical stimulation of the indicated subcortical formations is based on increased rhythmic oscillations within the theta-band and on a greater coherence in this range.