Figure 1.

Schematic representation of the core-shell model consisting of 2 groups of oscillators, the core (ventral part $\upsilon$ ) and shell (dorsal part $d$ ). Parameters $F$ and $w_F$ are the strength and frequency of an external light cue acting exclusively on the core. The core (shell) is characterized by a mean free-running frequency ${\overline{w}}_{u(d)}$ , the statistical spread of free-running frequencies ${∆}_{u(d)}$ (Lorentzian half width at half maximum), and the intracoupling $K_{uu(dd)}$ between oscillators within the core (shell). Coupling between core and shell oscillators is determined by intercouplings $K_{ud}$ (core on shell) and $K_{du}$ (shell on core).