[The role of the thalamic ventrolateral nucleus in the cortical effect on the activity of vestibular neurons]. / Rol' ventrolateral'nogo iadra talamusa v realizatsii kortikofugal'nogo vliianiia na aktivnost' vestibuliarnykh neironov.

Electrocoagulation of lateral vestibular nucleus (NVL) reduces inhibitory effect of the motor and somatosensory areas and enhances the inhibitory effect of limbic, vestibular, and orbital cortical areas. Facilitating effect was enhanced by electrostimulation of the motor area and reduced by the stimulation of other cortical areas. Following the coagulation of the NVL, the ascending afferent flow to the cortex seems to be reduced. This results in diminishing of the cortical neurones tone and readjusts the descending influences upon the NVL neurones activity.

[Cortical mechanisms of regulation of neuron activity of Deiters vestibular nucleus during vibration]. / Korkovye mekhanizmy reguliatsii aktivnosti neironov vestibuliarnogo iadra Deitersa pri vibratsii.

The peculiarities of the effect of vestibular, somatosensory, motor and limbic areas of brain cortex on the activity of neurons of lateral vestibular nucleus (LVN) are studied in the nembutal and chloralose anesthetized rabbits by the extracellular lead method before and after vibration exposure. It is found that the responses of neurons of Deiters's nucleus at all frequency ranges to stimulation of different areas of the cortex were predominantly of inhibitory type, being more pronounced during stimulation of the vestibular and motor areas. The facilitating corticofugal effect was noted in 20-30 % of cells and more pronounced influence was during stimulation of somatosensory and limbic areas of the cortex. During vibration there was a multidirectional effect of cortical areas on the neuronal activity of LVN. The vibration stimulus decreases an inhibitory effect and increases stimulating influence of vestibular cortex on the activity of Deiters's nucleus. The noted effect was more pronounced in neurons with low frequency of initial activity. On stimulation of other areas of the cortex an increase of inhibitory and suppression of facilitating descending effects were noted. The greatest amount of inhibited neurons was recorded during stimulation of motor cortex. The peculiarities and functional significance of the observed effects are discussed.