Date: Wed, May 10, 14:30-16:00
Venue: Room M203, Komaba Open Laboratory, The University of Tokyo
Invited Speaker: Dr. Hiroshi Kori (Department of Mathematics, Hokkaido University)

Title:  Entrainment of Complex Oscillator Networks:
Strong Impact of the Network Architecture and Implications for Design of
Biological Clocks

Abstract:
 Entrainment, i.e. synchronization to periodic external forcing, takes
place in our circadian clocks, which makes the clock exactly the 24h  period
and provides the ability to adapt to local time. In mammals,  circadian
timing throughout the body is coordinated by the master  clock in the brain
called the suprachiasmatic nucleus (SCN). The SCN  is composed of numerous
clock cells forming a complex neural  network. To entrain the SCN to local
daily rhythm, a distinct subset  of cells receives light information.
Entrainment ability of the  whole neural network is a crucial problem for
the function of the  biological clock.
  From this motivation, entrainment of randomly coupled oscillator  networks
by periodic external forcing applied to a subset of oscillators  is
numerically and analytically investigated. We find that the  entrainment
window with a tongue shape becomes exponentially narrower  and the
relaxation time becomes exponentially longer for the networks  with the
higher hierarchical organization. However, the entrainment  is significantly
facilitated if the networks are directionally  biased, i.e., closer to the
feedforward networks. The neural network  structure of the master clock of
the circadian rhythm in mammals is  discussed from the viewpoint of our
results. A experiment concerning  the entrainment ability is also proposed.