Seeing with Two Eyes: Integration of Binocular Retinal Projections in the Brain

In the visual system, accurate representation of images throughout each stage of processing requires the maintenance of topography in different but interconnected brain regions [1]. Topographic organisation also allows information from both eyes to be precisely integrated, underpinning depth perception and interpretation of the visual world. In the absence of this organisation within and between eye-specific projections, visual information becomes scrambled within the brain and function is compromised [2,3]. Despite advances in recent years that have given insight into the mechanisms responsible for topographic mapping of visual projections within the brain, comparatively less is known about the mechanisms that underpin the integration of binocular pathways. The aim of this review is to summarise what is known about the developmental processes that establish topography in binocular projections in key animal models. We review experiments in mice that examine the development of binocular projections to the superior colliculus and address the role of molecular guidance cues. We will also describe experiments in Siamese cats that shed light on the organisation of binocular projections to the lateral geniculate nucleus and visual cortex. Finally, we will discuss this research in the context of early diagnosis and rehabilitation strategies of loss of binocular vision in humans.