Figure 7.
Nullclines for different 2D biophysical models. A. In the Ih + Ip model with Gp = 0 (A1) different values of Gh lead to nullclines that are close to linear near the fixed point. In contrast, when Gp > 0 (A2; Gp = 0.5) the V-nullcline can show quadratic nonlinearities near the fixed point. B. Similarly in the IM + Ip model with Gp = 0 (B1) the nullclines are close to linear whereas when Gp > 0 (B2; Gp = 0.5) the V-nullcline shows quadratic nonlinearities. Note that the individual nullclines are qualitatively mirror images of those of the Ih + Ip model. In all panels filled circles denote stable fixed points and open circles denote saddle points.