title: A colourful clock.
abstract: Circadian rhythms are an essential property of life on Earth. In mammals, these rhythms are coordinated by a small set of neurons, located in the suprachiasmatic nuclei (SCN). The environmental light/dark cycle synchronizes (entrains) the SCN via a distinct pathway, originating in a subset of photosensitive retinal ganglion cells (pRGCs) that utilize the photopigment melanopsin (OPN4). The pRGCs are also innervated by rods and cones and, so, are both endogenously and exogenously light sensitive. Accumulating evidence has shown that the circadian system is sensitive to ultraviolet (UV), blue, and green wavelengths of light. However, it was unclear whether colour perception itself can help entrain the SCN. By utilizing both behavioural and electrophysiological recording techniques, Walmsley and colleagues show that multiple photic channels interact and enhance the capacity of the SCN to synchronize to the environmental cycle. Thus, entrainment of the circadian system combines both environmental irradiance and colour information to ensure that internal and external time are appropriately aligned.
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University medical School, Leiden, The Netherlands; Nuffield Laboratory of Ophthalmology; Sleep and Circadian Neuroscience Institute (SCNi) Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.
authors.forename: Hester C
authors.initials: HC
authors.lastname: van Diepen
authors.affiliation: Nuffield Laboratory of Ophthalmology; Sleep and Circadian Neuroscience Institute (SCNi) Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.
authors.forename: Russell G
authors.initials: RG
authors.lastname: Foster
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University medical School, Leiden, The Netherlands.
authors.forename: Johanna H
authors.initials: JH
authors.lastname: Meijer
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000528:radiation effects*; D002940:Circadian Rhythm / Q000528:radiation effects*; D003116:Color; D003118:Color Perception; D012165:Retinal Ganglion Cells / Q000528:radiation effects*; D013493:Suprachiasmatic Nucleus / Q000528:radiation effects*