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T M Efremova

Publications and source records attributed to T M Efremova.

At least 19 recordsLinked to original sources
PubMed1973

Power spectra of cortical electric activity in the rabbit in relation to conditioned reflexes.

In chronic experiments on rabbits spectral and correlation characteristics of cerebral cortical potentials were computed to study the elaboration of a conditioned defense reflex. was found that the frequency spectra of the EEG are subject to consistent changes: a narrow-band frequency constantly developing in the theta range. During exposure to a positive conditioned stimulus, the maximum of this frequency increased relative to the pre-stimulus period and a maximal coherence of electrical processes was observed in a narrow theta range between the electrical processes of the cortical analyzers to which the conditional and unconditional stimuli were addressed. Different relationship was noted in the theta range during presentation of a differential or extinguishing stimuli: it became slightly slower than in the pre-stimulus period, and the coherence of the theta rhythms was less than maximal, remaining high at the other frequencies. It was concluded that the presence of highly coherent electrical processes in the theta range is important for the formation of conditioned reflex in the rabbit cerebral cortex. The processes of internal inhibition are characterized electrographically by disagreement of electrical processes in the theta range in respect to phase or frequency.

Animals↗
PubMedDate not supplied

Participation of nonlinear dynamic processes in the formation of the high-frequency EEG of the rabbit.

The informativeness of the high-frequency EEG for the assessment of the functional state of the brain has been proven by means of a new method of analysis of the EEG which is suitable, by contrast with the traditional spectral correlation analysis, for the description of nonlinear processes. Evidence has been obtained in favor of the hypothesis that a deterministic chaotic component, the parameters of which depend on the region of recording of the EEG and which changes conjointly with change in the functional state of the brain, is present in the EEG of the neocortex and hippocampus of the rabbit.

Animals↗
PubMedDate not supplied

Chaotic components in the high-frequency EEG of rabbit cortex during formation of a conditioned defensive reflex.

The chaotic component of the high-frequency EEG of the rabbit cortex was studied during the development of a conditioned defensive reflex to nonrhythmic light stimulation with electric reinforcement applied to the animal's paw. Regular changes in the dynamic parameters of the chaotic component of the high-frequency EEG were demonstrated. Characteristic changes in the asymptotic evaluations of the correlational dimensionality of the attractor of the chaotic component (DCC) of the high-frequency EEG were detected in the cortical regions studied both during the action of the conditioned stimulus and in background conditions before presentation of combinations. These changes affected both the afferent and efferent cortical regions of the conditioned reflex arc, as well as regions not directly addressed by the conditioned or unconditioned stimuli. These results allow the dynamics of changes in the morphofunctional structures of the conditioned reflex to be seen at the cortical level during learning. Significant differences in the early and late stages of conditioned reflex formation were detected.

Aggression↗
PubMedDate not supplied

[Chaotic component of human high-frequency EEG in the state of quiet wakefulness].

Chaotic component of human EEG oscillations in the high-frequency band (14.7-100 Hz) was investigated. EEG was recorded from four points in symmetrical frontal and occipital scalp areas. The results of the non-linear analysis of the high-frequency EEG indicate the existence of the deterministic chaotic component with a high attractor correlation dimension. It was significantly different from the respective values of the Gaussian noise filtered in the same frequency band. In the state of quiet wakefulness (eyes closed), the dimensions of chaotic components of the EEG in all derivations did not differ from each other. Analysis of correlation pairs between the ensembles of correlation dimensions of the high-frequency EEG revealed reliable patterns of significant connections between the neocortical areas with individual features in different subjects. When the functional state of the brain was changed by hyperventilation, both the values of the correlation dimensions and the structure of inter-area connection patterns changed. We believe that the nonlinear component of high-frequency EEG is a sensitive and local characteristic of the functional state of the human brain.

Brain↗
PubMedDate not supplied

[The participation of nonlinear dynamic processes in the formation of the high-frequency EEG in the rabbit].

By means of a new method of the EEG analysis, suitable, in contrast to traditional correlative-spectral analysis, for description of nonlinear processes, the informativeness of high-frequency EEG is proved for evaluation of functional brain state. Evidences are obtained in favour to the hypothesis that in the rabbit neocortex and hippocampus EEG a determinate chaotic component is present whose parameters depend on the area of EEG recording and change together with the change of functional brain state.

Animals↗
PubMedDate not supplied

[Correlation between bioelectrical processes of the cortex, thalamus, midbrain reticular formation during formation of a defensive conditioned reflex in rabbits].

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.

Animals↗
PubMedDate not supplied

[Cytochemical changes in the nucleic acids and proteins in the limbic structures of the rabbit brain during formation of a defensive conditioned reflex].

The intensity of cytochemical changes of nucleic acids and proteins of neurones in structures of the limbic circle was studied with the method of two-wave visible cytospectrophotometry and histoautoradiography at the early and late stages of conditioned defensive reflex formation. It was shown that at both stages there occurs an intensification (of different degree) of cytochemical changes level in all of the studied limbic structures. A the late stage of reflex elaboration, there is a redistribution of the level of cytochemical changes in the studied brain structures. It is concluded that a specific morphofunctional system of activated brain structures corresponds to each behavioural situation.

Amygdala↗
PubMedDate not supplied

[Spectral-correlation analysis of high-frequency EEG components of the rabbit cerebral cortex during orienting and defensive responses].

A change was shown in the EEG power spectra of the sensorimotor, visual and auditory neocortical areas and the dorsal hippocampus, and corresponding coherence functions in the range of 14.6-110 c/s during an orienting reaction and the formation of a defensive conditioned reflex in rabbits. It was suggested that the rhythm of about 5 c/s appearing during formation of the conditioned reflex, serves for the functional integration of the brain structures which is specific for a certain functional state.

Animals↗
PubMedDate not supplied

[The dynamic characteristics of the chaotic component of the high-frequency EEG of the rabbit during the acquisition and extinction of the orientation reflex].

The chaotic component of the high-frequency EEG of the rabbit was studied during repeated presentation of non-rhythmical light stimuli. The chaotic component was found to be sensitive to the action of these stimuli, its reactions being variant in different cortical areas. Dimension changes were revealed corresponding to a manifestation of the phasic and tonic components of the orienting reaction. In the course of orienting reflex extinction the chaotic component characteristics changed in correspondence with the activation level shifts in the cortical areas under study.

Animals↗