title: Light responses of primate and other mammalian cones.
abstract: Retinal cones are photoreceptors for daylight vision. For lower vertebrates, cones are known to give monophasic, hyperpolarizing responses to light flashes. For primate cones, however, they have been reported to give strongly biphasic flash responses, with an initial hyperpolarization followed by a depolarization beyond the dark level, now a textbook dogma. We have reexamined this primate-cone observation and, surprisingly, found predominantly monophasic cone responses. Correspondingly, we found that primate cones began to adapt to steady light at much lower intensities than previously reported, explainable by a larger steady response to background light for a monophasic than for a biphasic response. Similarly, we have found a monophasic cone response for several other mammalian species. Thus, a monophasic flash response may in fact be the norm for primate and other mammalian cones as for lower-vertebrate cones. This revised information is important for ultimately understanding human retinal signal processing and correlating with psychophysical data.
authors.affiliation: Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, and Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors.forename: Li-Hui
authors.initials: LH
authors.lastname: Cao
authors.forename: Dong-Gen
authors.initials: DG
authors.lastname: Luo
authors.forename: King-Wai
authors.initials: KW
authors.lastname: Yau
mesh_terms: D000818:Animals; D006801:Humans; D008027:Light; D008252:Macaca fascicularis / Q000502:physiology*; D051379:Mice; D010775:Photic Stimulation; D051381:Rats; D017949:Retinal Cone Photoreceptor Cells / Q000528:radiation effects*; D013552:Swine; D014785:Vision, Ocular / Q000502:physiology*
keywords: mammal; monkey; phototransduction; retina