Abstract
The vertebrate retina is one of the most accessible parts of the central nervous system for clarifying the links between neural circuits and visual coding. Advanced imaging methods are already revealing fundamental features of retinal organization and function previously inaccessible to study. As a background for considering future directions I will review our current understanding of the cellular architecture of the primate retina. On the one hand, the retina is an elegantly simple structure at the periphery of the visual system where mosaics of receptor cells transmit signals to interneurons and ganglion cells whose axons project a representation of the visual world to the brain. However, the retina is also an amazingly complex neural machine that contains at least 80 anatomically and physiologically distinct cell populations. The interactions among most of these cell types are precisely arranged in a microlaminated sheet that provides the scaffold for ∼ 20 separate visual pathways. In the primate, much attention has been focused in the so-called ‘midget pathway’, yet these cells, despite their numerosity, only account for two anatomically distinct visual pathways. By contrast, the great majority of visual pathways exists at relatively low density and subserves diverse functions ranging from color vision and motion detection to the pupil reflex and setting biological rhythms. Microdissecting the structure and function of each of these diverse low-density pathways remains a key challenge for retinal neurobiology.