Stereoscopic vision depends on correct matching of corresponding features between the two eyes. It is unclear where the brain solves this binocular correspondence problem. Although our visual system is able to make correct global matches, there are many possible false matches between any two images. Here, we use optical imaging data of binocular disparity response in the visual cortex of awake and anesthetized monkeys to demonstrate that the second visual cortical area (V2) is the first cortical stage that correctly discards false matches and robustly encodes correct matches. Our findings indicate that a key transformation for achieving depth perception lies in early stages of extrastriate visual cortex and is achieved by population coding.
The information necessary for binocular depth perception may result via emergent properties of ensemble behavior. We demonstrate, with direct experimental evidence from both awake and anesthetized monkeys, that the integration of neuronal signals across a population may help to achieve binocular correspondence. We show that V2 could be a critical stage for solving the binocular correspondence problem. We suggest that the transformation from physical stimulus to perception begins to happen in V2 and might be inherited by higher cortical areas in both the dorsal and ventral pathways where complex 3D percepts are generated.
Fig. 1. Falsematching is discarded in V2 of anesthetized monkeys.
Fig. 2. Responses in V2 are not explained by the energy model.
Online Paper:
www.pnas.org/lookup/suppl/doi:10.1073/pnas.1614452114/-/DCSupplemental
Solving visual correspondence between the two eyes via domain-based population encoding in nonhuman primates