Vestibulopathy was produced by creating GPEE in the system of vestibular nuclei (Kryzhanovsky et al., 1976c). The functional structure of the vestibular complex is such that it may become the basis of the formation of GPEE of vestibular neurons under pathologic conditions when the inhibitory mechanisms are upset. The distinguishing features of the vestibular neurons includes their constant background impulse activity (De Vito et al., 1956; Gorgiladze, 1966; Wilson et al., 1966; Ito et al., 1969), which may be connected with the presence of proper multisynaptic pathways in the nucleus (Precht, Shimazu, 1965; Shimazu, Precht, 1965). These pathways are believed to be connected with the multipeak EPSP which originate in the secondary vestibular neurons when the vestibular nerve is stimulated (Ito et al., 1969b) and with the tonic vestibular neurons which originate after the monosynaptic response of the prolonged secondary discharges. Multisynaptic excitation in vestibular nuclei can be produced by intranuclear interneurons via the feedback system (Brodai et al., 1962). Besides the intranuclear mechanisms, the vestibular complex has many activating connections (Brodel et al., 1962). At the same time, vestibular neurons can apparently independently generate spontaneous impulses, as these impulses were recorded under the conditions of deep nembutal anesthesia, when the reticular formation and other areas of the central nervous system were ‘switched off’, and under the conditions of curarization, the removal of the cerebellum and the section of the vestibular nerves (Gorgiladze, 1966). The spontaneous impulse activity of the secondary neurons may be possibly caused by definite properties of their membrane (Bruggencate et al., 1972). The population of the secondary vestibular neurons is heterogeneous; more than five types of neurons have been ascertained in it (Shimazu, Precht, 1966). The neurons of type I are divided into tonic and phasic ones (Precht, Shimazu, 1965; Shimazu, Precht, 1965). Tonic neurons possess the properties of spontaneous impulse activity and a low threshold of their reaction to acceleration, and they slowly change the frequency of the impulse during acceleration. Kinetic neurons do not possess the properties of spontaneous impulse activity; they have a high excitation threshold as regards acceleration, and intermittently change the frequency of the impulse flow.
KeywordsVestibular Nucleus Vestibular Stimulation Vestibular Nerve Vestibular Neuron Lateral Vestibular Nucleus
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