On Tuesday, April 7, 2015,
David Berson, Dept. of Neuroscience, Brown University, will be presenting “Intrinsically Photosensitive Retinal Ganglion Cells” as part of the Light InSight Lecture Series.
A small subset of retinal ganglion cells exhibit robust light responses even when all influences from classical photoreceptors (rods and cones) are eliminated. These intrinsically sensitive retinal ganglion cells (ipRGCs) use a novel photopigment called melanopsin to generate their intrinsic light responses. Though discovered in rodents, ipRGCs are present in humans and, apparently, all other vertebrates. These neurons are essential for a variety of reflexive or homeostatic responses to environmental illumination, including photic synchronization of circadian rhythms, constriction of the pupil and neuroendocrine responses, photic pain, and modulation of sleep and mood. These findings help to explain why many physiological responses to light responses persist in mammals, including humans, with retinal blindness resulting from loss of rods and cones. We are pursuing many new lines of inquiry about these cells, including their unexpected diversity (comprising at least six types), their diverse functional roles in visually driven behavior, and their surprising ability to distribute their output signals within the retina itself. These ‘centrifugal’ signals appear to activity-dependent development of the visual system and retinal adaptation to environmental light.