This project investigates how a key brain region for visual processing combines sensory and non-sensory signals one synapse from the eye, using neural imaging and behavioural techniques that we have developed. The superficial layers of the Superior Colliculus (sSC) receive strong input from retina and are thought to send purely visual signals to the deeper layers that generate motor actions. Observations in our laboratory, however, show that sSC does more than pure vision: its visual responses are strongly shaped by non-sensory signals such as arousal and locomotion. We need to understand how the sSC performs this combination, both in terms of computation and of neural circuits involving different cell types. Moreover, we need to go beyond overall brain states and passive viewing, to probe interactive conditions where visual stimuli are used for specific decisions and actions. Finally, we need to understand to what extent the non-sensory signals received by sSC originate in the cerebral cortex, and how non-sensory signals combine with visual signals from the retina. We can now answer these questions thanks to novel 2-photon imaging, optogenetics and behavioural techniques that we have recently developed to study the activity of neurons in the sSC of awake, behaving mice. These experiments will shape our understanding of how the brain integrates sensory and non-sensory inputs. They will reveal how neurons one synapse away from retina already do much more than pure vision, combining visual signals with strong non-sensory signals related to brain state, to behavioural state, to decision, and to action.