[Study of the ancient tecto-thalamo-cortical pathway of the visual system in rats]

Recording the evoked potentials and neuronal activity, electrophysiological studies have been made on tecto-thalamo-cortical tract in rats. The existence of a system of efferent projections in the superficial, visual layers of the superior colliculi was shown which are diffusely present in the nucleus lateralis posterior (n. LP), indicating low level of morpho-functional organization of this region of the dorsal thalamus in rats. In response to electrical stimulation of the n. LP, in laterocaudal parts of the visual system (fields 17 and 18a of the cortex) the evoked potentials of primary-negative polarity were observed which are associated mainly with the superficial (I--IV) cortical layers. Predominant representation of tecto-thalamo-cortical system in the laterocaudal visual area of the cortex indicates the tendency to separate representation (with respect to cortical areas and cortical layers) of retino-geniculate and retino-tecal visual systems in rats.