Behavioural states control binocular vision through input-specific mechanisms.

Binocular vision is essential for high-acuity stereopsis, depth perception and goal-directed behaviours, but whether binocular visual processing is modulated according to an animal's behaviroal state remains unknown. By combining behavioural tracking with calcium imaging in layer 2/3 excitatory neurons in the binocular zone of the primary visual cortex (bV1) of adult mice, we demonstrate that binocularity and binocular integration change rapidly in a state-dependent manner via eye-/input-specific cellular mechanisms: responses to contralateral eye stimulation are strongly enhanced during high arousal states, much more so than ipsilateral responses, and binocular integration shifts from sublinear to supralinear summation, which both are explained by the differential modulation of thalamic and callosal inputs to bV1 neurons. We thus propose that the state-dependent modulation of bV1 neurons adapts an animal's visual perception to its behavioural demands by reducing the relative impact of binocular vision during high-arousal states while enhancing the impact of peripherally-derived monocular vision.