Cortical visual areas of the cat project differentially onto the nuclei of the accessory optic system.

Cortical projections to the nuclei of the cat's accessory optic system were demonstrated by anterograde transport and degeneration methods. Areas 21a, 21b, AMLS and PMLS were found to project to the medial, lateral and dorsal terminal accessory optic nuclei. Selective projections from area PLLS to the lateral terminal nucleus and from areas 17 and 18 to the medial terminal nucleus were noted. No terminal labeling was detected following injections of areas ALLS, DLS, 20a, 20b, 19, 7 or the splenial visual area. The accessory optic system has been implicated in the control of optokinetic nystagmus. Additional evidence supports a role for ipsilateral visual cortical projections in mediating optokinetic pursuit in the naso-temporal direction under monocular conditions. Thus the visual cortical projections we describe may partially underlie the observed functional laterality of monocularly elicited optokinetic pursuit in the cat. The present results further indicate that suprasylvian areas AMLS, PMLS and 21 are the cortical regions primarily responsible for descending visual influences on the cat's accessory optic nuclei.