Explorations of pulvinar circuitry in the northern greater galago (Otolemur garnettii)

Abstract

The pulvinar is the largest thalamic subdivision in primates and has deep integration with cortical areas involved with visual perception. Unlike the lateral geniculate nucleus (LGN), which acts as the primary relay in the visual system, the pulvinar’s nuclei receive most of their driving input from cortex. In this dissertation, I examine the structure and circuitry of the pulvinar complex of the northern greater galago (Otolemur garnettii), a phylogenetically ancient model organism comparable to the common ancestor of all primates.

Here, three anatomical tract tracing experiments are presented and analyzed in the greater context of higher order thalamic nuclear function. First, early visual cortical neurons projecting to the seemingly mirrored representation within visual pulvinar are labeled using retrograde tracers and examined using retrograde tracers. Then these tracers are used again to explore pulvino-cortical projections to frontal, temporal, and parietal cortices. Finally, we use anterograde tracers visualized using both confocal and electron microscopy to place our findings in the greater context of higher order thalamic nuclei. This volume concludes by proposing that the pulvinar complex functions as a thalamic target within the visual cortical hierarchy thus resulting in parallel processing streams.