Pulvinar connectivity has been studied using a variety of neuroanatomical tracing techniques in both New and Old World monkeys. Connectivity studies have revealed additional maps of the visual field other than those described using electrophysiological techniques, such as P3 in the capuchin monkey and P3/P4 in the macaque monkey. In this chapter, we argue that with increasing cortical size, the pulvinar developed new functional subdivisions in order to effectively interconnect and interact with the cortex.