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Biomedical subjects

B V Bakharev

Publications and source records attributed to B V Bakharev.

At least 19 recordsLinked to original sources
PubMed1991

[Cytoplasmic RNA in neocortical neurons in vitro].

The investigation of the ratio of neuronal cytoplasmic RNA mono- and two-chain sections was performed in thin neocortical slices by means of fluorescent probing. Changes of the relative intensity of Acridine Orange red luminescence indicated a decrease in the quota of monochain sections in the common neuronal RNA pool. In eight hours of superfusion it was authentically less than in the control slices and in the slices which were incubated during four hours. Deep profiles of red fluorescence became plane in the process of incubation. It was suggested that the essential decrease in the red luminescence intensity of cytoplasmic RNA in vitro, observed between four and eight hours, may be conditioned by disintegration of polysomes to monosomes, and this, in its turn, may cause the decrease in ribosomal synthetic activity.

Acridine Orange↗
PubMed1986

[Prolonged excitation of individual neocortical neurons. Structure of spontaneous firing].

Spontaneous firing of single neurons was studied during L-glutamate-induced stable activation in the cat cerebral cortex. The autocorrelation analysis of the trains of discharges showed, that periods of increased and decreased probability of discharges were constant in general. A single neuron seems incapable of radically affecting the interneurons connected with it. The type of spontaneous firing is mainly associated with the level of activation of the neuronal assembly where the neuron belongs.

Action Potentials↗
PubMedDate not supplied

Prolonged excitation of individual neocortical neurons, structure of background impulse activity.

The background impulse activity of individual neurons was recorded extracellularly in the cerebral cortex of the cat during the prolonged microionophoretic delivery to these neurons of L-glutamate. Glutamate ionophoresis ensured the transition of the neuron to an elevated, but stable level of activation. An autocorrelation analysis of the trains of impulses showed that in spite of the multiple rise in the average discharge frequency, the type of background impulse activity and the periods of increased and reduced probability of discharges for the most part remained constant. The obtained data indicate that an individual cell is unable to influence substantially the interneurons connected with it, while the type of background activity of a neuron is determined primarily by the level of activation of the cellular ensemble incorporating this neuron.

Animals↗
PubMedDate not supplied

Phase relationships between the rhythmic activity of cortical structures of the rabbit at different midbrain reticular formation stimulation frequencies.

An investigation of the phase shifts between rhythmic constituents of the electrical activity of the hippocampus, somatosensory, motor, and visual areas of the neocortex of the rabbit during an increase in the frequency of stimulation of the reticular formation from 60 to 1000 imp/sec revealed the fluctuating character of the decrease in the phase shift in the theta range in pairings involving the visual area and of its increase in the remaining pairings. In the delta range, at the same time, an increase was observed in the phase angle in pairings between the hippocampus, somatosensory, and motor areas at a stimulation frequency above 200 imp/sec, while in the alpha range the changes in the phase shift were variously directed in character.

Alpha Rhythm↗
PubMedDate not supplied

[Rhythmical processes in the cerebral cortex bioelectrical activity in arousal reaction: qualitative nonlinear analysis involving refractoriness].

An integral equation that takes into account the absolute and relative refractory periods of cortical cells was added to the earlier obtained integral equations describing the cooperation of excitatory and inhibitory neurons of the cerebral cortex, and its substantiation was suggested. The steady states and the stable region of oscillations of the mean membrane potential of excitatory neurons were investigated depending on the mean afferent influx value on the assumption of the normal threshold distribution of cells. The existence of a parameter multitude in the region of stability was shown when a suppression of the delta-rhythm and an enhancement of the theta-rhythm up to its dominance take place increasing nonspecific afferent influx, which shows up a white noise, and decrease of the theta-rhythm during further increase in nonspecific activation. Simultaneously the frequencies of the major cerebral rhythms increase. The conformity of the theoretically calculated dependences of changes of the spectrum upon increasing nonspecific afferent influx to the experimental data obtained during the electrical stimulation of the rabbit midbrain reticular formation was demonstrated.

Afferent Pathways↗
PubMedDate not supplied

[The influence of the potential dependence of the amplitude of postsynaptic potentials on rhythmic processes of bioelectric activity of the cerebral cortex].

The dependence of the postsynaptic potential amplitude on the membrane potential was entered into the earlier derived integral equations describing the interactions between excitatory and inhibitory populations of neocortical neurons. The influence of the potential dependence on steady states and the stable region of oscillations of the mean membrane potential of neurons were investigated. Encephalograms of humans and animals in different functional states were numerically simulated. The real form of a power spectrum of electroencephalogram was obtained. The occurrence of the nonregular spindle-shaped activity was revealed, which expands the frequency of basic oscillations and widens the spectral peak. In the unsteady region, the existence of a limiting cycle and the possibility of arising of the pathological activity observed upon abnormal brain functioning were shown with the help of the numerical nonlinear analysis.

Algorithms↗
PubMedDate not supplied

[Electroencephalogram structure].

The representation of an electroencephalogram as a convolution of harmonic functions having negative decrements with discrete (evenly discontinuous) white Gaussian noise was considered. A substantiation of this representation is given. It was numerically shown that the convolution of the decrement damping alpha-rhythm of one frequency with discrete white noise is a narrow-band chaos, an irregular spindle-shaped activity, which results in the appearance of close spectral components in the spectrum of power. The estimation of the autocorrelation function represented a damping cosinusoid shifted in phase depending of the factor of fading. The absolute value of convolution described an envelope of the output signal. The average duration of spindles decreased as the module of the decrement increased.

Cerebral Cortex↗
PubMedDate not supplied

[The cross-correlation relations of the electrical activity of the cortical structures at different levels of the activation of the midbrain reticular formation in the rabbit].

Changes of correlation coefficients and coherence of the delta-, theta- and alpha-rhythms were studied between the somatosensory, motor and visual neocortex areas, dorsal hippocampus and dentate fascia at stimulation frequencies of the midbrain reticular formation from 60 to 1000 imp/s. It was shown that correlation coefficient between the structures studied increased at 60-200 imp/s and decreased at the further increase of stimulation frequency. In pairs with the visual area the correlation coefficient changed but little. The delta-rhythms coherence tended to decrease with the increase of stimulation frequency. Coherence of the theta-rhythms between the neocortical areas and the hippocampus increased with the increase of stimulation frequency up to 200 imp/s and decreased at higher frequency stimulation while in pairs of these areas with the dentate fascia it continued to rise with the increase of stimulation frequency up to 1000 imp/s. The coherence of the alpha-rhythms was almost unchanged at 60-200 imp/s and mostly had an increase at higher frequency stimulation.

Alpha Rhythm↗
PubMedDate not supplied

[Dependence of the spectrum of electrical activity of the neocortex and hippocampus in rabbits on the intensity of the stimulation of the midbrain reticular formation].

Study of dominating spectral maxima in delta-, theta- and alpha-ranges of the electrical activity of rabbits' neocortex and hippocampus showed that an increase of the frequency of the mesencephalic reticular formation stimulation from 60 to 200 imp/s led in both structures to an enhancement of the theta-rhythm (up to 130% in the neocortex and 147% in the hippocampus) and suppression of delta- and alpha-activity (correspondingly up to 67 and 34% in the neocortex and 37 and 48% in the hippocampus) with subsequent weakening of this effect at frequency increase up to 1000 imp/s. In the hippocampus, the reticular stimulation was more effective with respect to the theta- and delta-rhythms, and in the neocortex--with respect to the alpha-rhythm. In both structures the theta-rhythm amplitude changed less than the amplitude of the delta- and alpha-activities. Dependence of the amplitude of dominating rhythms on intensity of reticular formation stimulation differed from the analogous frequency dependence of the same rhythms.

Animals↗
PubMedDate not supplied

[Cross-correlation analysis of the background activity of visual cortex cells separated by different distances in the alert rabbit].

Values of correlation coefficients (CC) and forms of cross-correlation functions of impulse activity were studied in neurones recorded with one microelectrode or simultaneously with two sticked together microelectrodes with tangential distance between tips of 70 and 140 mcm. Three main types of cross-correlation functions were singled out differing by peaks form and modes positions. The greatest variety of forms and the greatest percentage of significantly correlated discharges of cellular pairs were found among the neurones recorded with one electrode. Mean CC of cells recorded with one electrode was significantly greater than mean CC of the neurones recorded with two microelectrodes. Comparison of the character of intercellular correlation with amplitudes of recorded spikes showed that discharges of neurones with greater amplitude mainly forestalled discharges of cells with low amplitude.

Action Potentials↗
PubMedDate not supplied

[Electrophysiologic correlates of habituation and conditioned reflex elaboration].

The average correlation coefficient between the EEG of different parts of the cortex gradually decreases as the rabbit is habituated to the experimental surroundings. Elaboration of an electo-defensive conditioned reflex leads to its enhancement which is replaced by a phase of temporary decrease, to be followed again by an enhancement of EEG correlation. The pronouncedness of theta-frequencies in the spectral and coherent functions behaves in a similar way. Successive changes of delta-activity level reveal no regularity.

Animals↗