title: Relationship between Human Pupillary Light Reflex and Circadian System Status.
abstract: Intrinsically photosensitive retinal ganglion cells (ipRGCs), whose photopigment melanopsin has a peak of sensitivity in the short wavelength range of the spectrum, constitute a common light input pathway to the olivary pretectal nucleus (OPN), the pupillary light reflex (PLR) regulatory centre, and to the suprachiasmatic nuclei (SCN), the major pacemaker of the circadian system. Thus, evaluating PLR under short wavelength light (λmax ≤ 500 nm) and creating an integrated PLR parameter, as a possible tool to indirectly assess the status of the circadian system, becomes of interest. Nine monochromatic, photon-matched light stimuli (300 s), in 10 nm increments from λmax 420 to 500 nm were administered to 15 healthy young participants (8 females), analyzing: i) the PLR; ii) wrist temperature (WT) and motor activity rhythms (WA), iii) light exposure (L) pattern and iv) diurnal preference (Horne-Östberg), sleep quality (Pittsburgh) and daytime sleepiness (Epworth). Linear correlations between the different PLR parameters and circadian status index obtained from WT, WA and L recordings and scores from questionnaires were calculated. In summary, we found markers of robust circadian rhythms, namely high stability, reduced fragmentation, high amplitude, phase advance and low internal desynchronization, were correlated with a reduced PLR to 460-490 nm wavelengths. Integrated circadian (CSI) and PLR (cp-PLR) parameters are proposed, that also showed an inverse correlation. These results demonstrate, for the first time, the existence of a close relationship between the circadian system robustness and the pupillary reflex response, two non-visual functions primarily under melanopsin-ipRGC input.
authors.affiliation: Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, IMIB-Arrixaca, 30100, Espinardo, Murcia, Spain.
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Bonmati-Carrion
authors.affiliation: Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
authors.forename: Konstanze
authors.initials: K
authors.lastname: Hild
authors.affiliation: Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Isherwood
authors.affiliation: Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Sweeney
authors.affiliation: Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Revell
authors.affiliation: Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Skene
authors.affiliation: Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, IMIB-Arrixaca, 30100, Espinardo, Murcia, Spain.
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Rol
authors.affiliation: Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, IMIB-Arrixaca, 30100, Espinardo, Murcia, Spain.
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Madrid
mesh_terms: D002940:Circadian Rhythm; D006801:Humans; D008027:Light; D055537:Light Signal Transduction; D009043:Motor Activity; D011680:Pupil / Q000502:physiology*; D012025:Reflex, Pupillary; D013493:Suprachiasmatic Nucleus / Q000502:physiology