This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Danilenko, K. V. Articles by Terman, M. Search for Related Content PubMed PubMed Citation Articles by Danilenko, K. V. Articles by Terman, M. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Social Bookmarking                         What's this?

The Human Circadian Pacemaker Can See by the Dawn's Early Light

Institute of Physiology, Siberian Branch of the Russian Academy of Medical Sciences, Novosibirsk, Russia; Institute of Internal Medicine, Siberian Branch of the Russian Academy of Medical Sciences, 2a, Vladimirovsky spusk, Novosibirsk 630003, Russia.

Anna Wirz-Justice

Kurt Kräuchi

Centre for Chronobiology, Psychiatric University Clinic, CH-4025 Basel, Switzerland

Jakob M. Weber

Bühlmann Laboratories, CH-4124 Schönenbuch, Switzerland

Michael Terman

Columbia University & New York State Psychiatric Institute, New York, NY 10032, USA

The authors' previous experiments have shown that dawn simulation at low light intensities can phase advance the circadian rhythm of melatonin in humans. The aim of this study was to compare the effect of repeated dawn signals on the phase position of circadian rhythms in healthy participants kept under controlled light conditions. Nine men participated in two 9-day laboratory sessions under an LD cycle 17.5:6.5 h, < 30:0 lux, receiving 6 consecutive daily dawn (average illuminance 155 lux) or control light (0.1 lux) signals from 0600 to 0730 h (crossover, random-order design). Two modified constant routine protocols before and after the light stimuli measured salivary melatonin (dim light melatonin onset DLMOn and offset DLMOff) and rectal temperature rhythms (midrange crossing time [MRCT]). Compared with initial values, participants significantly phase delayed after 6 days under control light conditions (at least –42 min DLMOn, –54 min DLMOff, –41 min MRCT) in spite of constant bedtimes. This delay was not observed with dawn signals (+10 min DLMOn, +2 min DLMOff, 0 min MRCT). Given that the endogenous circadian period of the human circadian pacemaker is slightly longer than 24 h, the findings suggest that a naturalistic dawn signal is sufficient to forestall this natural delay drift. Zeitgeber transduction and circadian system response are hypothesized to be tuned to the time-rate-of-change of naturalistic twilight signals.

Key Words: dawn simulation • human circadian rhythms • constant routine • rectal temperature • melatonin

Journal of Biological Rhythms, Vol. 15, No. 5, 437-446 (2000)
DOI: 10.1177/074873000129001521


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				M. Comas and R.A. Hut Twilight and Photoperiod Affect Behavioral Entrainment in the House Mouse (Mus musculus) J Biol Rhythms, October 1, 2009; 24(5): 403 - 412. [Abstract] [PDF]

				W. Bachleitner, L. Kempinger, C. Wulbeck, D. Rieger, and C. Helfrich-Forster Moonlight shifts the endogenous clock of Drosophila melanogaster PNAS, February 27, 2007; 104(9): 3538 - 3543. [Abstract] [Full Text] [PDF]

				M. Terman and J. S. Terman Controlled Trial of Naturalistic Dawn Simulation and Negative Air Ionization for Seasonal Affective Disorder Am J Psychiatry, December 1, 2006; 163(12): 2126 - 2133. [Abstract] [Full Text] [PDF]

				K. V. Danilenko, C. Cajochen, and A. Wirz-Justice Is Sleep per se a Zeitgeber in Humans? J Biol Rhythms, April 1, 2003; 18(2): 170 - 178. [Abstract] [PDF]

				R. J. Cole, J. S. Smith, Y. C. Alcal, J. A. Elliott, and D. F. Kripke Bright-Light Mask Treatment of Delayed Sleep Phase Syndrome J Biol Rhythms, February 1, 2002; 17(1): 89 - 101. [Abstract] [PDF]