title: Human chronotypes from a theoretical perspective.
abstract: The endogenous circadian timing system has evolved to synchronize an organism to periodically recurring environmental conditions. Those external time cues are called Zeitgebers. When entrained by a Zeitgeber, the intrinsic oscillator adopts a fixed phase relation ψ to the Zeitgeber. Here, we systematically study how the phase of entrainment depends on clock and Zeitgeber properties. We combine numerical simulations of amplitude-phase models with predictions from analytically tractable models. In this way we derive relations between the phase of entrainment ψ to the mismatch between the endogenous and Zeitgeber period, the Zeitgeber strength, and the range of entrainment. A core result is the "180° rule" asserting that the phase ψ varies over a range of about 180° within the entrainment range. The 180° rule implies that clocks with a narrow entrainment range ("strong oscillators") exhibit quite flexible entrainment phases. We argue that this high sensitivity of the entrainment phase contributes to the wide range of human chronotypes.
authors.affiliation: Institute for Theoretical Biology, Humboldt University, Berlin, Germany.
authors.forename: Adrián E
authors.initials: AE
authors.lastname: Granada
authors.forename: Grigory
authors.initials: G
authors.lastname: Bordyugov
authors.forename: Achim
authors.initials: A
authors.lastname: Kramer
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Herzel
mesh_terms: D057906:Circadian Clocks / Q000502:physiology*; D004777:Environment; D006801:Humans; D008954:Models, Biological; D013997:Time Factors
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