Role of the posterolateral nucleus of the thalamus in mechanism of information transmission to the visual cortex.

It has been demonstrated in chronic experiments on wakeful rabbits that the posterolateral nucleus of the thalamus exerts tonic and phasic facilitatory influences on the formation of responses of the visual cortex elicited by a light flash. The tonic influences were expressed in an increase in the amplitude parameters of the responses of the visual cortex in conditions of the formation in the posterolateral nucleus of the thalamus of a focus of heightened excitability (anode polarization), and their perceptible diminution with potassium depression in this nucleus. The phasic influences were expressed in the formation in the visual cortex of thalamocortical responses elicited by pulse stimulation of the posterolateral nucleus of the thalamus, which displayed a close interaction with the responses of the cortex elicited by the light flash. This interaction consisted in a noticeable facilitation of the responses of the visual cortex against the background of a conditioning pulse stimulation of the posterolateral nucleus. The facilitatory effect of the phasic influences was more significant than the effect of the tonic influence.