Binocular Circuitry as a Model for Understanding Experience-Dependent Circuit Development across the Mammalian Cortex

The binocular circuitry in mammals (e.g., mice, cats, and primates) integrates two distinct visual cortical circuitries-the contralateral and ipsilateral eye circuitries-into a cohesive functional system for three-dimensional vision. These two circuitries, differing in their developmental timing and trajectories, demonstrate the intricate interplay between innate genetic programs and experience. The contralateral eye cortical circuitry, largely laid down by intrinsic mechanisms and maturing earlier, establishes an initial framework, whereas the later-developing ipsilateral eye circuitry, established and refined through visual experience, aligns with and is integrated into this framework to achieve precise functional connectivity. We propose that this mechanism of binocular circuitry development, wherein distinct circuits are progressively refined and integrated under the influence of environmental stimuli, exemplifies a fundamental organizing principle governing the development of the entire cortical architecture. Such integration enables different cortical areas to combine diverse streams of information, improving processing capabilities and optimizing neural circuits to support more sophisticated functions, ultimately facilitating advanced sensory-motor coordination and complex behaviors.