Different patterns of eye-specific input are relayed to overlapping populations in the mouse superior colliculus

Abstract

The mouse superior colliculus (SC) regulates critical behaviors such as prey capture and visual threat avoidance, each of which depend on binocular visual processing. In contrast to our previous understanding, recent work has demonstrated widespread and diverse binocular interactions in the mouse SC. The SC receives direct input from contralaterally and ipsilaterally projecting retinal ganglion cells (contra- and ipsi-RGCs), but the ways in which eye-specific information is filtered in the SC remain unclear. Here, we utilized a trans-synaptic, intersectional viral tracing strategy to label SC neurons receiving input monocularly from contra-RGCs (SC-C), monocularly from ipsi-RGCs (SC-I), or binocularly from both (SC-B). We show that a surprising number of SC neurons receive ipsi-RGC input and that the proportions of SC-C, SC-I, and SC-B neurons are consistent throughout the SC. Morphometric analysis revealed few differences between neurons receiving different eye-specific patterns of input. Consistent with this, we show that SC-C, SC-I, and SC-B neurons are comprised of similar proportions of five morphologically distinct subtypes. And, the expression of candidate molecular markers appears similar across innervation patterns. Together, these data suggest that eye-specific information is widespread throughout the SC targeting overlapping populations of neurons.