Transformations of photic information in melanopsin pathways - PROJECT SUMMARY/ABSTRACT Animal sense light for perception as well as the regulation of physiology and behavior. While cells in the retina that transmit photic information to the brain to support these latter ‘non image’ functions have been identified (the intrinsically photosensitive retinal ganglion cells: ipRGCs), it remains unclear what information they convey to the brain and how it is processed to support particular tasks. I propose to relate molecular and cellular mechanisms of ipRGCs to their signals within the brain, their influence on postsynaptic cells, and their drive of behavior. To enable these investigations, I established a paradigm for imaging visually-evoked Ca2+ dynamics and neurotransmitter release in the Olivary Pretectal Nucleus (OPN), the retinorecipient region that drives the pupillary light reflex (PLR), while simultaneously monitoring pupillary constriction and other mouse behaviors. Using this paradigm, I will investigate how melanopsin’s presence within the distal axon and the release of specific neurotransmitters from ipRGC axon terminals shapes the properties of the PLR (Aim 1). Adjustments in pupil size are likely to diverge from ipRGC signals in several important respects; for instance, due to arousal. To test this hypothesis, I will measure photic signals in postsynaptic cells of the OPN and assess their regulation by internal states (Aim 2). Together, these experiments will define how mechanisms in ipRGCs determine the photic information available in the brain and how downstream cells transform this information to meet the requirements of a visual reflex.
