Coherence and spike death induced by bounded noise and delayed feedback in an excitable system

The FitzHugh-Nagumo model with bounded noise and delayed feedback is numerically investigated. A minimum of the coefficient of variation (R) of interspike intervals is observed both as a function of the noise intensity and as a function of the noise correlation time, viz, the coherence resonance phenomenon. Also, in the scenario of purely noise-sustained irregular oscillations, there exists a maximum of R as a function of the delay time (τd) of feedback, namely, the suppressed coherence. Moreover, in the scenario of purely noise-sustained regular oscillations, the R with multiple peaks as a function of τd can be observed, that is, the oscillatory coherence. Additionally, within the tailored parameter regime, spike death phenomenon can be obtained. These results may be helpful for making artificial devices.