[The effect of scopolamine on the spatial organization of rat cortical potentials]. / Vliianie skopolamina na prostranstvennuiu organizatsiiu potenstialov kory golovnogo mozga krys.

The influence of scopolamine (1 mg/kg, i.p.) on the spatial organization of the neocortical electrical activity was studied in rats. A decrease in the spectral power and coherence of brain potentials in the range of the dominant theta-rhythm peak (6.00-7.25 Hz) and their increase in the adjacent low-frequency band were observed. Both indices were decreased in the wide beta band (19.00-30.00 Hz). The described changes took place over the whole areas of the right hemisphere and parieto-temporal region of the left hemisphere. The obtained results are discussed with respect to the role of the cholinergic brain system in the higher nervous activity.

[Changes in the direct and interhemispheric responses of the pyramidal tract after tetanization of the cortex and lateral hypothalamus]. / Izmenenie priamykh i mezhpolusharnykh otvetov piramidnogo trakta posle tetanizatsii kory i lateral'nogo gipotalamusa.

Changes in pyramidal tract response after unilateral neocortical and lateral hypothalamic tetanization were analyzed in unanesthetized and nonimmobilized rabbits. Membrane and synaptic modifications were revealed in intra- and interhemispheric connections. Changes in excitability of callosal collaterals of pyramidal tract neurons in contralateral hemisphere and changes in somatodendritic excitability in ipsilateral hemisphere could be oppositely directed. Plasticity of callosal connections may contribute to the interhemispheric asymmetry during learning.

Neurobiology of the integrative activity of the brain. Dynamics of the activational and inhibitory types of synchronization of cortical neurons during the realization of a defensive reflex and of internal inhibition.

An increase in synchronization of the activational type (coincidence of the presence of impulse activity), and a decrease of the inhibitory type (coincidence of both the presence and absence of impulse activity), in the operation of close-lying neurons were observed in the visual and sensorimotor areas of the new cortex and in the hippocampus of wakeful non-immobilized rabbits in response to the combination of flashes of light with electrodermal stimulation (EDS) of the extremity. An increase in the synchronization of the neurons of the inhibitory type took place in the visual cortex in response to flashes against the background of the conditional inhibitor, i.e., continuous light, and changes in synchronization, similar to the effect of pain reinforcement but significantly weaker, appeared in the sensorimotor cortex and in the hippocampus. An increase in synchronicity of the activational type took place primarily in pairs of neurons with increase in the same direction in the frequency of impulse activity in response to a stimulus, and of the inhibitory type, took place with its decrease. In addition, both kinds of changes in synchronization appeared in a significant portion of the pairs of neurons with changes in the frequency of impulse activity of different directions.

[The dynamics of the activating and inhibitory types of cortical neuron synchronization during the realization of a defensive reflex and internal inhibition]. / Dinamika aktivatsionnogo i tormoznogo tipov sinkhronizatsii neironov kory pri realizatsii oboronitel'nogo refleksa i vnutrennego tormozheniia.

In the visual and sensorimotor areas of the neocortex and in the hippocampus of alert nonimmobilized rabbits, in response to combinations of light flashes with electrocutaneous limb stimulation an increase was observed of synchronization in the activity of the near-by neurones by activation by inhibitory type (coincidence of the presence and absence of impulse activity). In response to flashes against the light background--conditioned inhibitor--in the visual cortex synchronization of neurones increased by inhibitory type, and in the sensorimotor cortex and hippocampus changes of synchronization appeared, similar to the action of pain reinforcement but considerably weaker. The increase of synchronization by the activation type took place mainly in the neurones pairs with unidirected increase of impulses frequency and by the inhibitory one--with its decrease. Along with this, in a considerable part of neurones pairs both changes of synchronization appeared at the impulses frequency changes of different direction.

[Study of phase relations of potentials in the rabbit cerebral cortex in various functional states]. / Issledovanie fazovykh otnoshenii potentsialov kory mozga krolika pri razlichnykh funktsional'nykh sostoianiiakh.

Phasic shifts of cortical biopotentials were studied in rabbits during background activity and photic stimulation. It has been found that in most cases the phasic shift of dominating theta-waves gradually increases with the distance between the electrodes both under conditions of the background activity and photic stimulation. This confirms the presence of the phase gradient at which most motor reactions are realized. Photic stimulation increases the number of synphasic oscillations in the EEG recorded from neighbouring points and decreases the dispersion of values of the phasic shift between the EEG of the sensorimotor and visual cortices, i.e. it makes phasic shifts more stable. Irradiation of excitation from the visual analyzer to the motor one in response to photic stimulation is realized in most cases against the background of high values of the correlation coefficients, coherent function and phasic shift from 0 to 10-11 degrees.

[Phase relationships of cerebral cortex potentials in the rabbit during the execution of motor responses]. / O fazovykh otnosheniiakh potentsialov kory mozga krolika pri osushchestvlenii dvigatel'noi reaktsii.

EEG waves phase relations in the sensorimotor and visual cortical areas were studied in 12 rabbits before and during a motor reaction in response to light stimulation. Phase relations in the background activity were characterized by a considerable dispersion (from 26 to 45 degrees). Light stimulation increased the quantity of synphasic EEG oscillations in adjacent cortical points and stabilized the phase shift between EEG waves in the sensorimotor and visual cortical areas. Motor reactions of rabbits to light occurred when theta-rhythm with the most constant phase shift was observed in the EEG of these areas.

[Spatial-phase relations of dominant fluctuations of brain potentials in the rabbit]. / Prostranstvenno-fazovye otnosheniia dominiruiushchikh kolebanii potentsialov mozga u krolikov.

Phase shifts of cortical electrical activity and their role in excitation irradiation from the visual zone to the motor one were studied in rabbits before and during light stimulation. Different variations of the phase relations were observed both in the background activity and during stimulation. In most cases, however, a gradual increase in the theta-waves phase shift was observed parallel with an increase in the distance between the recording electrodes. The most motor reactions were carried out by the animal, if a phase shift gradient was expressed. Therefore the brain status characterized by spatial phase gradient of the theta-waves was supposed to be optimal for realization of the motor reaction. Light stimulation increased the quantity of synphasic oscillations between EEG processes in the points situated not far from each other and decreased the variability of the phase shift value between the sensorimotor and visual cortex, i.e. stabilized the phase gradient. This stabilization was expressed in the increase of wave coherence. Motor reactions of the rabbit in response to stimulation were realized when the most stable phase shift between the theta-waves in the sensorimotor and visual cortex was recorded.

[Significance of theta-rhythm phases for excitatory transmission in the cerebral cortex]. / O znachenii faz teta-ritma dlia peredachi vozbuzhdeniia v kore golovnogo mozga.

The dependence of the number of motor reactions on the phase of theta-rhythm in the cerebral cortex, during which photic stimuli were presented was studied on unanaesthetized rabbits. Single flashes were presented to animals with 1--15 min intervals when theta-rhythm was dominant in the visual cortex. Each experimental session included 10--45 photic stimuli. It was found that the probability of rabbit's motor reaction to a photic stimulus depends on the phase of the theta-rhythm with which it coincides. The onset of a motor reaction to light in the majority of cases coincided with the positive phase of the theta-rhythm, which seems to be an optimal condition for the transmission of excitation in the cortex. The number of movements in response to light increases when the amplitude of the positive theta-rhythm oscillation is greater than the negative one. Recurrent inhibition in neural systems of the cerebral cortex seems to limit irradiation of excitation in case of big theta-rhythm amplitudes.

[Correlation between the theta rhythm energy characteristics in the cortex and motor reactions in rabbits]. / O korreliatsii énergeticheskikh kharakteristik teta-ritma v kore s dvigatel'nymi reaktsiiami u krolika.

The effect of the theta-rhythm energy on the transmission of excitation from the visual analyser to the motor one was studied in an automatized controlled experiment. It has been found that the probability of motor reaction to a photic stimulus correlates with definite energetic characteristics of theta-rhythm in the sensorimotor and visual cortical areas. Most favourable for the appearance of rabbit's motor response to photic stimulation is the similarity of mean theta-rhythm values in different cortical areas. It is assumed that recurrent inhibition in neuronal cortical systems delimits the excitation irradiation in the cortex in the case of high theta-rhythm amplitudes.

[Spatial synchronization of rabbit brain biopotentials upon repeated electrical stimulation of the cortex]. / Prostranstvennaia sinkhronizatsiia biopotentsialov bol'shogo mozga krolika pri povtornykh élektricheskikh razdrazheniiakh kory

A study was made on 23 rabbits of the degree of spatial synchronization in response to repeated electrical stimulations of one or simultaneously two cortical areas: the sensorimotor or visual, or simultaneously the sensorimotor and visual, or sensorimotor and precentral respectively. Enhancement of the synchronization induced by the stimulation, globally spread over the entire cortex and was followed by its decrease. However, in the two directly stimulated areas of the cortex, the similarity of bioelectrical oscillations persisted for a long time, which testifies to the establishment of selective relations between them.