Abstract
The koniocellular (K) layers of the dorsal lateral geniculate nucleus (LGN) and the calbindin-rich subdivisions of the inferior pulvinar nucleus are considered part of a thalamic matrix system which projects diffusely to superficial cortical layers. Activity in the matrix system is proposed to coordinate oscillatory activity in thalamocortical loops. Here we studied connections of LGN K layers and IPul in marmosets following injections of retrograde tracer, Fast Blue, in V1 and V2. We adopted a high-throughput neuro-histology pipeline, which enabled simultaneous brain region identification based on cytoarchitecture and fluorescent tracer localization. A computational routine was established to automatically cross-register fluorescent neurons to individual subdivisions of LGN and IPul. We found that both V1 and V2 receive inputs from K layers and IPul, whereas dominant outputs of magnocellular and parvocellular layers of LGN were to V1 only. Retrograde labeled cells in lateral division of IPul merged seamlessly into the retrograde labeled cells in K layers. We hypothesize that the K layers and IPul form a contiguous functional subdivision of the dorsal thalamic matrix.
