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

The superior colliculus (SC) is the main brain region regulating defensive behaviors to visual threats. Yet, how the SC integrates binocular visual information and to what extent binocular vision drives defensive behaviors remains unknown. Here, we show that SC neurons respond to binocular visual input with diverse synaptic and spiking responses, summating 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. We further show that binocular vision facilitates visually evoked escape behavior. Together, our data shed light on the cellular and circuit mechanisms underlying binocular visual processing in the SC and its role in defensive behaviors to visual threats.