Contributions of Retinal Direction Selectivity to Central Visual Processing

The brain monitors the sensory environment via signals from the sensory periphery, such as the olfactory epithelium, the inner ear, and the retina. Understanding how sensory stimuli are processed throughout the sensory hierarchy, and how this relates to behavior, is a central outstanding question in the field of neuroscience. The processing of visual motion in mice offers unique opportunities for addressing these questions thanks to a rich literature on the anatomical and physiological properties of motion-sensitive neurons across the visual system, paired with recent developments of cutting-edge genetic and imaging approaches. A visual scene typically contains motion originating from either moving objects or optic flow caused by self-generated movements. Neurons encoding the direction of visual motion are said to be 'direction-selective'. It was historically believed the circuits responsible for creating direction selectivity de novo exist within the visual cortex. Yet, in mice, direction-selective responses can be found already in the retina, suggesting in this model organism visual motion analysis starts at the earliest stage of the visual hierarchy. This minireview presents emerging literature demonstrating how retinal direction-selective cells make causal contributions to central visual motion processing and visually guided behaviors in mice, and their potential clinical relevance, and outlines experiments for testing remaining questions. Research in this field will undoubtedly continue to advance our understanding of the basic principles of the visual system and how sensory neurons extract fundamental features of the world.