Document Detail

Human circadian pacemaker is sensitive to light throughout subjective day without evidence of transients.
MedLine Citation:
PMID:  9374826     Owner:  NLM     Status:  MEDLINE    
Fifty-six resetting trials were conducted across the subjective day in 43 young men using a three-cycle bright-light (approximately 10,000 lx). The phase-response curve (PRC) to these trials was assessed for the presence of a "dead zone" of photic insensitivity and was compared with another three-cycle PRC that had used a background of approximately 150 lx. To assess possible transients after the light stimulus, the trials were divided into 43 steady-state trials, which occurred after several baseline days, and 13 consecutive trials, which occurred immediately after a previous resetting trial. We found that 1) bright light induces phase shifts throughout subjective day with no apparent dead zone; 2) there is no evidence of transients in constant routine assessments of the fitted temperature minimum 1-2 days after completion of the resetting stimulus; and 3) the timing of background room light modulates the resetting response to bright light. These data indicate that the human circadian pacemaker is sensitive to light at virtually all circadian phases, implying that the entire 24-h pattern of light exposure contributes to entrainment.
M E Jewett; D W Rimmer; J F Duffy; E B Klerman; R E Kronauer; C A Czeisler
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  273     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1997 Nov 
Date Detail:
Created Date:  1997-12-16     Completed Date:  1997-12-16     Revised Date:  2014-09-05    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  R1800-9     Citation Subset:  IM; S    
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MeSH Terms
Biological Clocks / physiology*
Body Temperature
Circadian Rhythm / physiology*
Grant Support
K01 AG000661/AG/NIA NIH HHS; K01 AG000661-05/AG/NIA NIH HHS; P01-AG-09975/AG/NIA NIH HHS; R01-AG-06072/AG/NIA NIH HHS; R01-MH-45130/MH/NIMH NIH HHS
C A Czeisler / Brigham & Women's Hosp, Boston, MA

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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