title: Optimal implementations for reliable circadian clocks.
abstract: Circadian rhythms are acquired through evolution to increase the chances for survival through synchronizing with the daylight cycle. Reliable synchronization is realized through two trade-off properties: regularity to keep time precisely, and entrainability to synchronize the internal time with daylight. We find by using a phase model with multiple inputs that achieving the maximal limit of regularity and entrainability entails many inherent features of the circadian mechanism. At the molecular level, we demonstrate the role sharing of two light inputs, phase advance and delay, as is well observed in mammals. At the behavioral level, the optimal phase-response curve inevitably contains a dead zone, a time during which light pulses neither advance nor delay the clock. We reproduce the results of phase-controlling experiments entrained by two types of periodic light pulses. Our results indicate that circadian clocks are designed optimally for reliable clockwork through evolution.
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Hasegawa
authors.affiliation: Center for Information Biology, National Institute of Genetics, Shizuoka 411-8540, Japan and RIKEN Center for Sustainable Resource Science, Kanagawa 230-0045, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Arita
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000502:physiology*; D006224:Cricetinae; D006801:Humans; D008954:Models, Biological; D010507:Periodicity