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A Threshold Equation for Action Potential Initiation

Figure 4

Influence of Na inactivation and ionic conductances on spike threshold in the conductance-based model (ka = 3.4 mV, see Materials and Methods).

A, Spike threshold θ as a function of Na+ inactivation variable h, with all other ionic conductances suppressed. B, Threshold as a function of K+ activation variable n, without inactivation (h = 1). C, Threshold as a function of total synaptic conductance (excitatory ge and inhibitory gi), relative to the resting conductance gL (conductances are considered static).

Figure 4