The inferior pulvinar complex in owl monkeys: architectonic subdivisions and patterns of input from the superior colliculus and subdivisions of visual cortex

Abstract

Patterns of connections with other visual structures and architectonic characteristics were used to subdivide the inferior pulvinar complex of owl monkeys into three distinct nuclei termed the central inferior pulvinar, IPc, the medial inferior pulvinar, IPm, and the posterior inferior pulvinar, IPp. IPc occupies about 70%; IPm about 20%, and IPp about 10% of the inferior pulvinar complex. Encapsulating fiber bands distinguish the boundaries of the three nuclei. IPm is also identified by a much greater packing density of neurons than IPc and IPp. Both IPp and IPc receive input from the superior colliculus, but the terminations in IPp are denser. Visual cortical Areas 17, 18, MT, DM, M and PP (Allman and Kaas, '76) project to IPc and IPm in patterns that indicate that central vision is represented dorsorostrally and peripheral vision ventrocaudally in both nuclei. Terminations in IPm from Area MT are particularly dense. None of these visual areas projects to IPp. Rather, input to IPp appears to originate in cortex rostral to Area MT in the temporal lobe.