Figure 4

Reversible \(\text{F} \leftrightarrow \text{SD}\) state transitions induced by blocking \(I_{\text{CaH}}\). A. Blocking \(I_{\text{CaH}}\) switches the model from its F to its SD state. Spike firing resumes in response to a hyperpolarizing pulse of injected current (\(-2\times 10^{3}~\mbox{nAcm}^{-2}\), 100 ms). B. The model can also be switched back to its firing mode by a depolarizing pulse (\(2 \times 10^{4}~\mbox{nAcm}^{-2}\), 100 ms). C. Bifurcation diagrams in the standard model and after blocking \(I_{\text{CaH}}\) show that coexistence of the branch of FP and the isola of LC remains after blocking \(I_{\text{CaH}}\). Blocking \(I_{\text{CaH}}\) induces the \(\text{F}\to \text{SD}\) transition by reducing the attraction basin of the sLC (see text). D. In the presence of a depolarizing bias current, blocking \(I_{\text{CaH}}\) fails to trigger the \(\text{F} \to \text{SD}\) transition, despite the membrane potential transiently goes above the undershoot of the uLC, \(V_{U_{\text{uLC}}}\) (blue box)