Retinal projections to the inferior and medial pulvinar nuclei in the Old-World monkey.

Horseradish peroxidase (HRP) and wheat germ agglutinin conjugated to HRP (WGA-HRP) were used as anterograde tracers to study the macaque monkey retinofugal pathways. Labeled axons were mapped beyond the lateral geniculate nucleus to the inferior (PI) and medial (PM) pulvinar nuclei, where they terminated. Retinofugal fibers project to the medial part of PI, adjacent to the brachium of the superior colliculus. A smaller projection to PM leaves the ventrolateral aspect of the lateral geniculate nucleus and travels parallel to the stria terminalis to reach the dorsal surface of the thalamus and PM. HRP reaction product was bilateral in PI and predominantly contralateral in P)M.