Fig. 2

Top: a plateau-like or fold/Hopf bursting starts after the spiking manifold $M_{\mathrm{lc}}$ becomes tangent to the middle, saddle branch of $M_{\mathrm{eq}}$ and terminates further through the reverse supercritical Andronov-Hopf bifurcation on the upper depolarized branch of $M_{\mathrm{eq}}$. Bottom: the primary feature of the square-wave bursting activity in the HR model also referred to as of fold/homoclinic type is the termination of the spiking manifold $M_{\mathrm{lc}}$ by the homoclinic bifurcation in the phase space of the fast subsystem. In both cases: fold stands for a saddle-node bifurcation at the turning point (SN) on the lower, hyperpolarized branch of $M_{\mathrm{eq}}$.