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The relationship between phase and period responses to light pulses
journal contribution
posted on 2002-07-01, 00:00 authored by Mark StokesMark Stokes, S Kent, S ArmstrongCurrent theories of stable circadian entrainment postulate phase delays should be associated with period lengthening, while phase advances should be associated with period shortening. While characterising features of the rat PRC to light, we noted substantial numbers of responses that displayed the opposite pattern. Forty-eight rats provided data for 192 phase responses. Limiting our analysis to phase shifts greater than 1 hour, we found 44 displayed the expected predicted relationship, and 33 displayed the contrary paradoxical relationship. Paradoxical responders possessed significantly shorter initial activity periods, compared to predicted responders. Activity was significantly lengthened by paradoxical responders and shortened by predicted responders following light pulse exposure. These results suggest a second mode of stable entrainment. Additionally, these results indicate entrainment mode, predicted or paradoxical, is based upon activity period duration. Short activity period durations will be associated with paradoxical responses, long durations will be associated with predicted responses. We argue that, given the dynamic changes in photoperiod, both modes of entrainment are necessary to provide stable entrainment across the year.
History
Journal
Biological rhythm researchVolume
33Issue
3Pagination
303 - 317Publisher
Swets and Zeitlinger BVLocation
Lisse, NetherlandsPublisher DOI
ISSN
0929-1016Language
engPublication classification
C1 Refereed article in a scholarly journalCopyright notice
Swets and ZeitlingerUsage metrics
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Science & TechnologyLife Sciences & BiomedicineBiologyPhysiologyLife Sciences & Biomedicine - Other Topicscircadian rhythmsentrainmentphase response curvesperiod responsesmultiple light pulseslight pulsesratFREE-RUNNING PERIODCIRCADIAN PACEMAKERSFUNCTIONAL-ANALYSISNOCTURNAL RODENTSACTIVITY RHYTHMSSYRIAN-HAMSTERCLOCKFREQUENCY
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