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Biomedical subjects

V V Lavrov

Publications and source records attributed to V V Lavrov.

7 recordsLinked to original sources
PubMed1992

[The activation and inhibitory postactivation effects of chemical interoceptive stimulation under normal conditions and in experimental neurosis].

The realisation of hemointeroceptive effects was found to begin with a period of the brain activation. In normal conditions a positive correlation was found between the EEG arousal response and the concentration of mustard administered into the stomach. In experimental neurosis, both regulatory influences of the hemointeroceptive stimulation were decreased.

Animals↗
PubMed1991

[An increase in the excitability of nonspecific cortical formations during a decrease in the level of influences from the brain stem reticular formation].

In chronic experiments on alert unrestrained cats with cortical implanted electrodes, the thresholds of EEG activation to electrical stimulation were investigated in normal cats and in animals with diminished influences from the mesencephalic RF. Comparative analysis of the thresholds revealed an increase of the cortical unspecific excitability in diminished reticular influences. The relation of this increase to the neurophysiological mechanisms of neurotic pathology is discussed.

Animals↗
PubMedDate not supplied

Increase in excitability of cortical nonspecific structures in the presence of a decreased level of influences from the brainstem reticular formation.

The results of the measurement of the threshold of electrical stimulation of the cortex sufficient to elicit the EEG activation reaction in the norm and under conditions of the reduction of influences from the brainstem of the reticular formation are presented. A decrease in the thresholds was observed in those conditions which are regarded as evidence of an increase in the excitability of the nonspecific cortical formations. The increase was uneven: it was maximal in the sensorimotor and minimal in the visual cortex. It is hypothesized that the data obtained in brain preparations with a decreased level of brainstem reticular influences may be applied to the understanding of certain phenomena of neurotic pathology in its neurophysiological aspect.

Animals↗
PubMedDate not supplied

[Electrical reactions in the cat brain during differentiation of photic stimuli].

Study of EEG responses to photic conditioned stimuli in cats has shown that the extent of brain activation depends not on the physical strength of the stimulus, but on its biological significance. The longest activation is recorded to a positive signal, even if it is the weakest flash of light. The intensity of EEG responses to negative stimuli is determined by the nearness of their physical parameters to those of the positive signal. Repeated presentation of a non-reinforced flash leads to a gradual extinction of EEG reactions. Brain activation in response to a reinforced positive signal persists unchanged even after a large number of its repetitions. The revealed properties of brain electrical reactions to stimuli of different significance accord with those previously recorded in response to acoustic stimuli. In both cases the data are in agreement with hypothesis of a central system of signal analysis, which performs the estimation of stimuli according to their biological quality.

Animals↗
PubMedDate not supplied

[The regulatory effect of the functional status of the cat on the perception of an external afferent stimulus].

Experiments were conducted on cats by conditioned food-procuring method. Behavioural, vegetative reactions and a set of electrophysiological characteristics were recorded. It was found that regulatory influence of an extraneous stimulus and of artificial excitation of the brain was expressed in an increase of reactivity to conditioned and unconditioned sensory stimuli and in disinhibition of effector responses. This influence was realized not only during the development of EEG activation reaction but could be preserved over a long period in conditions of the deactivated brain state. Regulatory influence of interceptive factors is characterized by a decrease of reactivity and by inhibition of effector responses. As in the case of external effects, the realization of this influence begins with a period of brain activation and is preserved for a long time in conditions of deactivated state.

Afferent Pathways↗
PubMedDate not supplied

[Analysis of photic signals by cats according to their intensity following transection of the superior quadrigeminal brachii].

In experiments on cats trained by the motor alimentary conditioned method to discriminate photic stimuli by intensity, EEG changes were studied when differentiating signals of different biological significance before and after transection of the brachii of the superior colliculi. The normal direct proportional dependence of pronouncedness of brain electrical reactions on the complexity of stimuli analysis was disturbed after transection. The operated animals retained only the capacity for a rough differentiation by brightness, the fine gradation of EEG responses to negative signals of different fineness being lost. The disturbance of interaction between the analysing and activating brain systems after transection of the brachii may be due to both the lack of non-specific ascending tonic influences of the midbrain reticular formation on the cortex, and to the destruction of many pathways for corticofugal control of the activity of the brainstem non-specific apparatus.

Animals↗