Responses to conflicting binocular stimuli in mouse primary visual cortex.

Binocular vision requires that the brain integrate input from both eyes to form a unified percept. Small interocular differences support depth perception (stereopsis), while larger disparities can cause diplopia or binocular rivalry. The neural mechanisms by which early visual circuits process concordant versus conflicting binocular signals remain incompletely understood, particularly in the case of large disparities. Here, we used visually evoked potential (VEP) recordings, unit recordings, and 2-photon calcium imaging in the binocular region of mouse primary visual cortex (bV1) to examine how distinct forms of binocular disparity engage local circuits. Using a dichoptic display, we found that interocular phase disparities reduced VEP magnitude through decreased neuronal firing early in the response (40-80 ms after stimulus onset). In contrast, orientation disparities also decreased VEP magnitude, but via increased firing later in the response (100-200 ms). This late activity was enhanced in both regular-spiking (putative excitatory) and fast-spiking (putative parvalbumin-positive inhibitory) units. In contrast, calcium imaging revealed that somatostatin-positive interneurons were suppressed during orientation conflict. These findings suggest that phase differences suppress bV1 responses via feedforward mechanisms, while orientation disparities prolong activity through disinhibition mediated by somatostatin-positive interneurons. Our results identify distinct circuit pathways recruited by different forms of binocular conflict, clarify how early visual cortex contributes to binocular integration, and provide a foundation for investigating perceptual suppression and rivalry.