Equivalence of the NaKL SSN model and the Hodgkin–Huxley model. a The equivalence between the two models is demonstrated by synchronizing the SSN model to membrane voltage oscillations synthesized by the Hodgkin–Huxley model (black line). The Hodgkin–Huxley time series voltage was assimilated over a 1000-ms-long window (green line) under the constraints of the current injection protocol (blue line). The membrane voltage was predicted from t = 1000 ms onwards by forward integrating the current protocol with the completed SSN model (red line). b, c Membrane voltages predicted by the same SSN model (red line) and HH model (black line) for two different current protocols. d Detail of the SSN and HH action potentials and a comparison of NaT and K gate variables in e the HH model and f the SSN model.