The photobiology of the human circadian clock

In modern society, the widespread use of artificial light at night disrupts the suprachiasmatic nucleus (SCN), which serves as our central circadian clock. Existing models describe excitatory responses of the SCN to primarily blue light, but direct measures in humans are absent. The combination of s...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 119; no. 13; pp. 1 - 8
Main Authors Schoonderwoerd, Robin A., de Rover, Mischa, Janse, Jan A. M., Hirschler, Lydiane, Willemse, Channa R., Scholten, Leonie, Klop, Ilse, van Berloo, Sander, van Osch, Matthias J. P., Swaab, Dick F., Meijer, Johanna H.
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 29.03.2022
Subjects
Biological clocks
Biological Sciences
Broadband
Circadian Clocks
Circadian rhythm
Circadian Rhythm - physiology
Circadian rhythms
Functional magnetic resonance imaging
Humans
Light
Light emitting diodes
Light levels
Medical imaging
Narrowband
Neuroimaging
Photobiology
Suprachiasmatic nucleus
Suprachiasmatic Nucleus - physiology
Wavelengths
melanopsin
photoreceptors
fMRI
suprachiasmatic nucleus
cones
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Summary:In modern society, the widespread use of artificial light at night disrupts the suprachiasmatic nucleus (SCN), which serves as our central circadian clock. Existing models describe excitatory responses of the SCN to primarily blue light, but direct measures in humans are absent. The combination of state-of-the-art neuroimaging techniques and custom-made MRI compatible light-emitting diode devices allowed to directly measure the light response of the SCN. In contrast to the general expectation, we found that blood oxygen level–dependent (BOLD) functional MRI signals in the SCN were suppressed by light. The suppressions were observed not only in response to narrowband blue light (λmax: 470 nm) but remarkably, also in response to green (λmax: 515 nm) and orange (λmax: 590 nm), but not to violet light (λmax: 405 nm). The broadband sensitivity of the SCN implies that strategies on light exposure should be revised: enhancement of light levels during daytime is possible with wavelengths other than blue, while during nighttime, all colors are potentially disruptive.
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Author contributions: R.A.S., L.H., C.R.W., L.S., M.J.P.v.O., and J.H.M. designed research; R.A.S., M.d.R., L.H., C.R.W., L.S., I.K., M.J.P.v.O., and J.H.M. performed research; S.v.B. contributed new reagents/analytic tools; R.A.S., M.d.R., L.H., C.R.W., L.S., I.K., M.J.P.v.O., and D.F.S. analyzed data; J.A.M.J., S.v.B., and J.H.M. developed the LED device; D.F.S. was responsible for the performance and analysis of human histology; and R.A.S., M.d.R., J.A.M.J., and J.H.M. wrote the paper.
Edited by Joseph Takahashi, The University of Texas Southwestern Medical Center, Dallas, TX; received October 15, 2021; accepted February 8, 2022
ISSN:0027-8424
1091-6490
1091-6490
DOI:10.1073/pnas.2118803119