Divergent photic thresholds in the non-image-forming visual system: Entrainment, masking and pupillary light reflex

Matthew P. Butler, Rae Silver

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

Light is the principal cue that entrains the circadian timing system, but the threshold of entrainment and the relative contributions of the retinal photoreceptors-rods, cones and intrinsically photosensitive retinal ganglion cells - Are not known. We measured thresholds of entrainment of wheel-running rhythms at three wavelengths, and compared these to thresholds of two other non-image-forming visual system functions: Masking and the pupillary light reflex (PLR). At the entrainment threshold, the relative spectral sensitivity and absolute photon flux suggest that this threshold is determined by rods. Dim light that entrained mice failed to elicit either masking or PLR; in general, circadian entrainment is more sensitive by 1-2 log units than other measures of the non-image-forming visual system. Importantly, the results indicate that dim light can entrain circadian rhythms even when it fails to produce more easily measurable acute responses to light such as phase shifting and melatonin suppression. Photosensitivity to one response, therefore, cannot be generalized to other non-image-forming functions. These results also impact practical problems in selecting appropriate lighting in laboratory animal husbandry.

Original languageEnglish (US)
Pages (from-to)745-750
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Volume278
Issue number1706
DOIs
StatePublished - Mar 7 2011

Keywords

  • Circadian
  • Photoreceptor
  • Retina
  • Suprachiasmatic nucleus
  • Wavelength

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

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