COHERENCE RESONANCE IN A NOISE-DRIVEN EXCITABLE SYSTEM

We study the dynamics of the excitable Fitz Hugh-Nagumo system under e xternal noisy driving. Noise activates the system producing a sequence of pulses. The coherence of these noise-induced oscillations is shown to be maximal for a certain noise amplitude. This new effect of coher ence resonance is explained by different noise dependencies of the act ivation and the excursion times. A simple one-dimensional model based on the Langevin dynamics is proposed for the quantitative description of this phenomenon.