ABSTRACT This request for supplemental funding under PA-23-189 is to support the postbaccalaureate research of Pearl Miller, who graduated from Northeastern University in 2023 with a bachelor’s degree in Cellular and Molecular Biology. Ms. Miller recently joined Dr. Michael Do’s laboratory at Boston Children’s Hospital and Harvard Medical School. The parent grant (R01 EY034089) for this proposed supplement concerns how the processing of sensory information emerges from actions at the molecular, cellular, and circuit levels. The experiments center on intrinsically photosensitive retinal ganglion cells (ipRGCs) of the mouse and their drive of pupillary constriction. IpRGCs produce their own light responses using a molecule called melanopsin, receive input from circuits that are driven by rod and cone photoreceptors, and innervate the olivary pretectal nucleus (OPN; a brain region that drives pupil constriction). How the properties of ipRGCs and their inputs influence the OPN and pupil is unknown. Ms. Miller will address this open question in behaving mice, by simultaneously measuring pupillary constriction and the activity of ipRGC presynaptic terminals within the OPN. She will ask how phototransduction in ipRGCs (Aim 1) and rods (Aim 2) shape terminal activity and pupil constriction. The proposed experiments will yield basic knowledge of photoreceptive mechanisms and pupillary control. In addition to pursuing this research, Ms. Miller will be immersed in a broad and deep training environment that provides for the cultivation of scientific and career skills, and that also offers assistance in applying to graduate programs. These experiences will provide a strong foundation for Ms. Miller to pursue her goal of becoming a physician, researcher, and teacher. She meets NIH’s criteria for PA-23-189 and fulfills its interest in diversity as articulated in NOT-OD-20-031.