Chia-Sheng Lin

Projections from the medial nucleus of the inferior pulvinar complex to the middle temporal area of the visual cortex.

Medial, central and posterior nuclei have been previously identified within the inferior pulvinar complex of owl monkeys (Lin & Kaas, 1979). In the present experiments injections of [3H]-proline into the posterior thalamus, including the medial nucleus, produced densely labeled terminals in the middle temporal area of the visual cortex (Allman & Kaas, 1971). Injections of the retrograde tracer, horseradish peroxidase, into the middle temporal area labeled most of the neurons in the medial nucleus and only occasional neurons in the central and posterior nuclei. The posterior nucleus appeared to project to the cortex rostral to the middle temporal area in the temporal lobe, and the central nucleus projects to the visual cortex caudal to the middle temporal area. We conclude that the middle temporal area is the major cortical target of the medial nucleus in the inferior pulvinar complex and that the central and posterior nuclei have other cortical targets. Thus, these findings support the view that the inferior pulvinar complex consists of three distinct nuclei, which should lead to further progress in understanding its connections and functions.