Form and Function of S-cone Opponent Circuits in the Primate Retina

Abstract

Visual information is carried from the retina by the axons of >20 ganglion cell types, which project throughout the brain. While many of these parallel pathways are cone-opponent, not all the color information leaving the retina is used for color perception, as many ganglion cells instead mediate non-image forming visual functions. However, our understanding of how the visual system uses spectral information is currently limited to the most common cone-opponent ganglion cells and their role in color perception. This thesis aims to expand our understanding of both how and why the visual system extracts color information by investigating the diversity S-cone opponent ganglion cells. I investigated the diverse visual functions mediated by color-coding circuits in the macaque parafovea by combining 3D reconstructions of retinal circuits from serial electron microscopy with single cell electrophysiology, computational models and human psychophysics. When the spatial arrangement of cone-opponent inputs is taken into account, this work reveals cone-opponent receptive fields can contribute to a diverse range of visual functions beyond hue perception, such as edge detection and circadian photoentrainment. More generally, the work in this thesis is inconsistent with the standard view of primate vision that emphasizes cortical processing and limits the role of retinal coding to efficient compression and transmission of visual information. Instead, the complexity and diversity of cone-opponent processing reported here indicates that the retina may play a more active role in the computations defining visual perception and behavior.