Projection of the mammalian superior colliculus upon the dorsal lateral geniculate nucleus: Organization of tectogeniculate pathways in nineteen species

Abstract

Anterograde and retrograde transport methods have been used to analyze the projection of the superior colliculus upon the dorsal lateral geniculate nucleus in 19 mammalian species. Our retrograde findings reveal that tectogeniculate neurons are relatively small, and lie dorsally within the superficial gray. These small tectogeniculate neurons are spatially related to a dense tier of W-cell retinal input. Our anterograde tracing results show that tectogeniculate axons are visuotopically distributed to small-celled regions of the lateral geniculate in all nineteen species. In the majority of these species, the small-celled, tectally innervated regions of the lateral geniculate lie adjacent to the optic tract and contain W-cell-like neurons. Our findings suggest that neuroanatomical demonstration of the tectogeniculate projection is a relatively simple and straightforward way of revealing regions of the lateral geniculate which contain W-cells. This is true even in species in which the lateral geniculate lacks obvious cellular laminae, and in regions of the lateral geniculate where W-cells are few in number. The present data are especially interesting in light of the cortical projections of tectally innervated, small-celled regions of the lateral geniculate to the patches or puffs within layer III of area 17. Since these regions of small-celled geniculocortical axons are co-extensive with zones ("blobs") rich in cytochrome oxidase, it might be that information carried over the tectogeniculate circuitry plays an important role in the functions of the blob system.

Demonstration of artificial visual percepts generated through thalamic microstimulation

“…The results presented thus far do not rule out the possibility that electrical stimulation in our task directly drives saccades, for instance, by engaging motor pathways via retinal collaterals to the superior colliculus (19) or by retrograde stimulation of tectothalamic projections from the superior colliculus (20), rather than generating a visual percept to which the animal reacts. We therefore performed additional experiments (two in each animal) in which two targets were presented in quick succession and the animals were required to saccade to them sequentially.…”

Morphologically Distinct Classes of Relay Cells Exhibit Regional Preferences in the Dorsal Lateral Geniculate Nucleus of the Mouse

“…This area, also known as the dorsal lateral shell, is distinct from other regions of dLGN because it contains a high concentration of calbindin-positive cells and serves as the recipient zone for the collilculo-geniculate projection (Reese, 1984;Grubb and Thompson, 2004). This region shares a similar homology to the tecto-recipient zones noted in the C-laminae of carnivores (Demeulemeester et al, 1991) and the koniocellular division of some primates (Harting et al, 1991). At least three classes of identified direction-selective RGCs project to this area: a group of Off cells that respond to upward motion (Kim et al, 2008(Kim et al, , 2010 superior colliculus and thus may be part of a unique colliculo-geniculate feedback loop that involves information conveyed by these RGC types.…”

Neural bases of the non-conscious perception of emotional signals

“…Although the superior colliculus projects to the inferior parts of the pulvinar 76 , and the amygdala receives projections from the medial pulvinar 109 , direct connections between the inferior and medial nuclei of the pulvinar remain to be described. Moreover, the superior colliculus also projects directly to the intercalated layers of the lateral geniculate nucleus 110 , and it was shown recently that , the optic tectum and the nucleus rotundus (Rt; an analogue of the visual pulvinar (Pulv)) in the thalamus (Th), and the amygdala (AMG). The visual Wulst area (Vis; the analogue to the mammalian primary visual cortex) is also displayed.…”

“…145). The superior colliculus is also connected to extrastriate areas through the pulvinar 76 and the lateral geniculate nucleus 110 , and activity in these cortical areas can persist after destruction of V1 but not after subsequent destruction of the superior colliculus 146 . Therefore, these direct mechanisms also affect cortical visual processes when the emotional stimulus is perceived nonconsciously, modulating extrastriate functions in a precise, category-specific, fashion 147,148 .…”