JOURNAL OF BIOLOGICAL RHYTHMS / June 2000Oda et al. / PACEMAKER MODELING Modeling the Dual Pacemaker System of the tau Mutant Hamster

Abstract Circadian pacemakers in many animals are compound. In rodents, a two-oscillator model of the pacemaker composed of an evening (E) and a morn-ing (M) oscillator has been proposed based on the phenomenon of “splitting” and bimodal activity peaks. The authors describe computer simulations of the pacemaker in tau mutant hamsters viewed as a system of mutually coupled E and M oscillators. These mutant animals exhibit normal type 1 PRCs when released into DD but make a transition to a type 0 PRC when held for many weeks in DD. The two-oscillator model describes particularly well some recent behavioral experiments on these hamsters. The authors sought to determine the relationships between oscillator amplitude, period, PRC, and activity duration through computer simulations. Two complementary approaches proved useful for analyzing weakly coupled oscillator systems. The authors adopted a “distinct oscillators ” view when considering the component E and M oscillators and a “system ” view when considering the system as a whole. For strongly coupled systems, only the system view is appropriate. The simulations lead the authors t