Binocular processing facilitates escape behavior through multiple pathways to the superior colliculus

The superior colliculus (SC) is the main brain region regulating innate defensive behaviors to visual threat. Yet, how the SC integrates binocular visual information and to what extent binocular vision drives defensive behaviors is unknown. Here, we show that binocular vision facilitates visually-evoked escape behavior. Furthermore, we find that SC neurons respond to binocular visual input with diverse synaptic and spiking responses, and summate visual inputs largely sublinearly. Using pathway-specific optogenetic silencing we find that contralateral and ipsilateral visual information is carried to binocular SC neurons through retinal, interhemispheric and corticotectal pathways. These pathways carry binocular visual input to the SC in a layer-specific manner, with superficial layers receiving visual information through retinal input, whereas intermediate and deep layers rely on interhemispheric and corticotectal pathways. Together, our data shed light on the cellular and circuit mechanisms underlying binocular visual processing in the SC and its role in escape behavior.