Figure 4.

Single thin spikes are more energetically expensive than single thick spikes and the cost of a fast-spike train is minimized with fast sodium inactivation. a, Hodgkin-Huxley model of an action potential with a slow potassium activation superimposed on the resulting sodium (orange) and potassium currents (red), and the total number of transferred ions (blue). Right, Hodgkin-Huxley model of an action potential with a fast potassium activation has a thinner width and larger number of transferred ions (blue). b, The energy cost of a Hodgkin-Huxley model with fast spiking is minimized when the sodium inactivation speed is matched to the potassium activation speed. Adapted from Hasenstaub et al. (2010).