Fig. 12

Dynamics of the WCI system (Equations 9a-9c) at $r_x=-4.76$. (a)-(d) Time series of the voltage variable x at several values of k, with k decreasing from top to bottom. The traces in frames (a) and (b) are at the same value of k and illustrate bistability. (e) Bifurcation diagram upon variations of parameter k, including branches of fixed points (black curve) and periodic orbits (two red curves, indicating maximal and minimal values of x over the orbit). Solid/dashed curves indicate stable/unstable solutions. The torus bifurcation at $k\simeq 0.7580$ is supercritical. At smaller values of k, direct numerical simulations show that the system exhibits bursting (□, indicating maximal and minimal values of x) and AM spiking (△, indicating extrema of the modulation envelope).