Melanopsin-expressing photosensitive retinal ganglion cells (pRGCs) represent a third class of retinal photoreceptor. These cells are intrinsically photosensitive, but also receive inputs from rod and cone photoreceptors, acting as the primary sensory conduit mediating non-image-forming responses to light. Multiple subtypes of pRGC have been described in… (More)
Retinal photoreceptors entrain the circadian system to the solar day. This photic resetting involves cAMP response element binding protein (CREB)-mediated upregulation of Per genes within individual cells of the suprachiasmatic nuclei (SCN). Our detailed understanding of this pathway is poor, and it remains unclear why entrainment to a new time zone takes… (More)
Melanopsin (OPN4) is a retinal photopigment that mediates a wide range of non-image-forming (NIF) responses to light including circadian entrainment, sleep induction, the pupillary light response (PLR), and negative masking of locomotor behavior (the acute suppression of activity in response to light). How these diverse NIF responses can all be mediated by… (More)
A recent study defines a novel role of melanopsin-expressing ipRGCs, showing that these inner retinal photoreceptors function as retinal irradiance detectors and provide a local measure of luminance to regulate functional adaptation in the mammalian retina.