Fig. 1

Example trajectories from Eq. (2) for the four different parameter regimes using the parameter values given in Table 1. a supra-threshold, b supersinusoidal, c critical, d subthreshold. In the supra-threshold regime spikes occur regularly and often; in the supersinusoidal regime spikes cluster near the peak of the sine wave; in the critical regime they occur less often; and in the subthreshold regime, spikes occur rarely. For all regimes, $\Omega =1$