LAUSR

Light regulates physiology, mood, and behavior through signals sent to the brain by intrinsically photosensitive retinal ganglion cells (ipRGCs). How primate ipRGCs sense light is unclear, as they are rare and challenging to target for electrophysiological recording. We developed a method of acute identification within the live, ex vivo retina. Using it, we found that ipRGCs of the macaque monkey are highly specialized to encode irradiance (the overall intensity of illumination) by blurring spatial, temporal, and chromatic features of the visual scene. We describe mechanisms at the molecular, cellular, and population scales that support irradiance encoding across orders-of-magnitude changes in light intensity. These mechanisms are conserved quantitatively across the ~70 million years of evolution that separate macaques from mice. Description Encoding illumination in primates Light is an important environmental factor for most organisms because it regulates many physiological functions and behaviors. Central to this regulation is a photoreceptive molecule called melanopsin and its actions within the intrinsically photosensitive retinal ganglion cells (ipRGCs), neurons that send signals from the retina to the brain. Little is known about the ipRGCs of primates. Liu et al. developed a method of identifying primate ipRGCs and used it to investigate how they sense the visual world (see the Perspective by Martin). They found that ipRGCs encode the overall intensity of environmental illumination using specializations that are distributed across scales of biological organization. These cells thus show insensitivity to image detail and a wide dynamic range. —PRS A rare type of primate retinal neuron encodes irradiance by blurring across space, time, and wavelength.