Propagating beats and fibrillation in a cellular automata model of an excitable medium

We examine some predictive features of a cellular automata model that describes the propagation of a travelling signal in an excitable media. The model has been used to demonstrate that it can degenerate into fibrillation via the mechanisms consistent with physiological causes. This non-stimulated fibrillation behaviour is spontaneous and is maintained indefinitely. Due to its simplicity, large system sizes can be simulated for long periods. Such long-time simulations are used here to analyse the relationship of the measured beat pattern to that of the spatial dependency of the propagating signal. Specifically the spectrum of a fibrillating beat signal is examined. It is found that the spectrum changes in form between that obtained in the early stages and that when the fibrillation matures. This change is related to the increasing state of disorder that fibrillation generates. This increase in disorder can be observed more clearly in the spatial structure of the beats.