CORTICAL PROJECTIONS OF INFERIOR PULVINAR AND ADJACENT LATERAL PULVINAR IN RHESUS-MONKEY (MACACA-MULATTA) - AUTORADIOGRAPHIC STUDY

An autoradiographic technique was used to determine superior colliculus (SC) and pulvinar projections in the rhesus monkey. SC projected bilaterally to the inferior pulvinar (PI) while occipital cortex projected to PI and the lateral pulvinar (PL). PI had sustaining, topographical projections to layers IV, III and I of areas 18 and 19 (and VI and I of 17) which agreed with the central representation of the visual hemifield and suggests that there is more than 1 nemifield representation in prestriate cortex. PL adjacent to PI also projected to the same cortical areas and layers, while the portion of PL extending into the caudal pole of the pulvinar projected to layers IV, III and I of areas 20 and 21. Occipital cortices were associated by cortico-thalamocortical connections and also received direct lemniscal input via SC-PI and the dorsal lateral geniculate nucleus (DLG), while inferotemporal areas 20 and 21 received only cortico-thalamocortical connections. Apparently Stoffel''s principle of lamellation holds, 1 pulvinar subdivision projects to several cortical areas, adjacent pulvinar subdivisions have overlapping projections to these cortical areas and their layers and the pulvinar also projects to the same cortical area as DLG but to different layers. These connections were similar to those in lower mammals but not to those in the squirrel monkey and bushbaby.