The Foveal Visual Representation of the Primate Superior Colliculus

A defining feature of the primate visual system is its foveated nature. Processing of foveal retinal input is important not only for high-quality visual scene analysis but also for ensuring precise, albeit tiny, gaze shifts during high-acuity visual tasks. The representations of foveal retinal input in the primate lateral geniculate nucleus and early visual cortices have been characterized. However, how such representations translate into precise eye movements remains unclear. Here, we document functional and structural properties of the foveal visual representation of the midbrain superior colliculus. We show that the superior colliculus, classically associated with extra-foveal spatial representations needed for gaze shifts, is highly sensitive to visual input impinging on the fovea. The superior colliculus also represents such input in an orderly and very specific manner, and it magnifies the representation of foveal images in neural tissue as much as the primary visual cortex does. The primate superior colliculus contains a high-fidelity visual representation, with large foveal magnification, perfectly suited for active visuomotor control and perception. •Primate superior colliculus (SC) is highly sensitive to foveal visual input•SC visually sensitive neurons sample foveolar visual space non-uniformly•SC magnifies foveal visual images in neural tissue as much as primary visual cortex•Tiny foveal stimuli activate large SC tissue area due to fixational eye movements Chen et al. show that superior colliculus (SC) is highly sensitive to foveal visual input and that it magnifies foveal image representation much more than previously anticipated. Their topography data, with large foveal magnification, show that tiny foveal stimuli can activate a large portion of SC neural tissue due to fixational eye movements.