Figure 3.

The critical manifold is projected onto the (c, V)-plane for (a) g_K = 5.1 nS, g_BK = 0.4 nS and (b) g_K = 4 nS, g_BK = 0.4 nS. L^- and L⁺ are the lower and upper fold curves, respectively. P(L^-) and P(L⁺) are the projections of L^- and L⁺. The shaded regions are singular funnels which are delimited by the curves L⁺ and the strong canards (SC, green curves). The singular periodic orbits (black curves with arrows) are superimposed. FN is a folded node singularity. δ < 0 in panel (a) and δ > 0 in panel (b).