Effects of high-frequency cyclic input and noise on interspike intervals in the coupled Bonhoeffer-van der Pol (BVP) model are studied with computer simulation. When two BVP elements are weakly coupled and cyclic input or noise is added to the first element, the interspike intervals of the second element decrease non-monotonically as the amplitude of the input increases. Further, complicated bifurcations in the interspike intervals are caused by cyclic input in the coupled BVP model in the oscillating state. Effects of the coupling on small rotations due to noise and the interruption of oscillations due to cyclic input, which occur when the equilibrium point is close to the critical point, are also studied. The non-monotonic changes and bifurcations in the interspike intervals are attributed to the phase locking of the coupled elements.

Coherence resonance in propagating spikes generated by noise in spatially distributed excitable media is studied with computer simulation and circuit experiment on the FitzHugh-Nagumo model. White noise is added to the one end of the media to generate spikes, which propagate to the other end. The mean and standard deviation of the interspike intervals of the spikes after propagation take minimum values at the intermediate strength of the added noise. This shows stronger coherence than obtained in the previous studies.