Title Contribution of human melanopsin retinal ganglion cells tosteady - state pupil responses

The recent discovery of melanopsin-containing retinal ganglion cells (mRGCs) has led to a fundamental reassessment of non-image forming processing, such as circadian photoentrainment and the pupillary light reflex. In the conventional view of retinal physiology, rods and cones were assumed to be the only photoreceptors in the eye and were, therefore, considered responsible for non-image processing. However, signals from mRGCs contribute to this nonimage forming processing along with cone-mediated luminance signals; although both signals contribute, it is unclear how these signals are summed. We designed and built a novel multiprimary stimulation system to stimulate mRGCs independently of other photoreceptors using a silent-substitution technique within a bright steady background. The system allows direct measurements of pupillary functions for mRGCs and cones. We observed a significant change in steady-state pupil diameter when we varied the excitation of mRGC alone, with no change in luminance and color. Furthermore, the change in pupil diameter induced by mRGCs was larger than that induced by a variation in luminance alone: that is, for a bright steady background, the