Fig. 1

Dimensionless parameters α and ϵ as a function of the biophysical resonant conductances in two representative conductance-based models. The models are described in Appendix B. a$I_{\mathrm{h}}+I_{\mathrm{Nap}}$ model with slow $I_{\mathrm{h}}$ and fast $I_{\mathrm{Nap}}$ (biophysical conductances: $G_{\mathrm{h}}$ and $G_{\mathrm{p}}$, respectively). b$I_{\mathrm{Ks}}+I_{\mathrm{Nap}}$ model with slow $I_{\mathrm{Ks}}$ and fast $I_{\mathrm{Nap}}$ (biophysical conductances: $G_{\mathrm{q}}$ and $G_{\mathrm{p}}$, respectively). For small enough values of $G_{\mathrm{p}}$ (dashed curves) both α and ϵ are positive for all values of $G_{\mathrm{h}}$ and $G_{\mathrm{q}}$ (a and b, respectively), while for larger values of $G_{\mathrm{p}}$ (solid curves) both α and ϵ are negative for large values of $G_{\mathrm{h}}$ and small values of $G_{\mathrm{q}}$ (in a and b, respectively). Note that although $I_{\mathrm{h}}$ and $I_{\mathrm{Ks}}$ are resonant currents, both α and ϵ exhibit different monotonic properties as $G_{\mathrm{h}}$ (a) and $G_{\mathrm{q}}$ (b) increase