Selective binocular integration in mouse visual cortex: binocular but not monocular neurons respond distinctly to congruent stimuli

Even though binocular integration is a foremost example of integrative computations in the brain, it remains unknown how the visual cortex mediates it. Here, we investigated neuronal responses to binocular stimuli in layers 2/3 of mouse primary visual cortex (V1) and lateromedial (LM) area with in vivo two-photon imaging. We presented mice with three types of binocular stimuli: congruent gratings, orthogonal gratings and a flashing Mondrian pattern in binocular conflict with a grating. We looked for congruency-specific responses to the binocular stimuli, but found that most neurons responded homogeneously across stimulus types. Responses of cells with a strong monocular preference for the contralateral eye responded similarly to monocular and binocular stimulation, while responses of cells with a preference for ipsilateral stimuli showed a strong but nonspecific suppression to all binocular stimuli. Only cells without a strong monocular preference (i.e. binocular cells) exhibited linear integration of monocular responses to incongruent stimuli and binocular facilitation to congruent gratings. Responses to ipsilateral components of a binocular display were found to be poor predictors of binocular responses regardless of eye preference of individual cells. We conclude that most neuronal responses to binocular stimuli in mouse V1 & LM are uninformative about the congruency of the monocular components, with the exception of binocular cells which show either linear or supralinear integration.