Fig. 10

Bifurcation structure of the I-cell (without gamma or theta input, i.e. System (1) subject to (3) with \(a=b=0\)) with respect to \(I_{\mathit {ton}}\) when A: \(g_{M}=1.5\) mS/cm² and B: \(g_{M}=0\) mS/cm². When \(g_{M}=1.5\) mS/cm², the stable fixed point ends at a subcritical Hopf bifurcation. A family of stable limit cycles is born at a saddle-node bifurcation of cycles. There is a bistability window of \(I_{\mathit {ton}}\) values such that a stable fixed point and a stable limit cycle coexist. When \(g_{M}=0\) mS/cm², the stable fixed points terminate and a family of stable limit cycles is born at a SNIC bifurcation