Noise-sustained pulsating patterns and global oscillations in subexcitablemedia

The constructive role of noise in an excitable activator-inhibitor medium i s analyzed. Noise acts parametrically on the excitation threshold of the sy stem, and is seen to support the existence of pulsating spots in the subexc itable regime. Increasing values of the noise intensity in this regime lead to a collective state in which all the elements of the system fire synchro nously. The spectral characteristics of the resulting global oscillations a re also studied as a function of the noise intensity, showing the typical f ingerprint of stochastic resonance. [S0031-9007(99)09016-X].