Parameter dependence of stochastic resonance in the stochastic FitzHugh-Nagumo neuron

Recently, the phenomena of stochastic resonance(SR) have attracted much attention in the studies of the excitable systems, in particular, the nervous system, under inherent noise. We study SR in a stochastic FitzHugh-Nagumo (FHN) neuron under Ornstein-Uhlenbeck noise and periodic stimulus, focusing on the dependence of SR phenomena on the stimulus parameters. Similar to the case of the Hodgkin-Huxley neuron, we find that the dependence of the critical forcing amplitude, above which resonance disappears and optimal noise intensities with maximal amplification of periodic stimulus, on the frequency of the periodic stimulus shows a bell-shaped structure with a minimum near the natural frequency. This frequency dependence of SR is explained in connection with the firing onset bifurcation curve of the FHN neuron in the deterministic situation. We also find that the critical forcing amplitude and optimal noise intensity of the stochastic bistable system has a monotonous structure which are also explained through the bifurcation curve of switching dynamics in the deterministic conditions for a wide range of forcing frequency.