[Effect of the motor cortex on heterogeneous afferent flows in the mediodorsal nucleus of the thalamus].

In experiments carried out on cats anaesthetized with Nembutal evoked potentials were recorded in the thalamic mediodorsal (MD) nucleus and in the projection and motor cortical areas with local cooling of the latter and the use of either single or paired stimuli of the same or different modalities. Visual and somatic excitatory inflows to the MD have been established, involving signals of specific and reticular genesis. Coming by separate ways they form isolated populations of neurones in the MD. A facilitating modulating influence of MD has been defined on the realization of afferent bursts produced in the motor cortex by visual and, particularly, somatic stimuli. It was found that in spite of its polyfunctionality, the motor cortex specifically influences heterogeneous inflows to the MD, exerting a more intensive and different action on the somatic afferentation as compared with the visual one. It is assumed that the specific and direct influence of the motor cortex on these impulses is exercised due to a functional subdivision of its corticofugal pathway into separate subsystems.