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A Balance Equation Determines a Switch in Neuronal Excitability

Figure 1

The bottom figures illustrate the typical phase portrait of restorative (left) and regenerative (right) excitability.

The dark (resp. light) blue circle denotes a stable restorative (resp. regenerative) steady state . The thin full (resp. dashed) curve is the voltage (resp. slow variable) nullcline. The saddle point in the right phase portrait is represented by a cross and its separatrix as the green oriented curve. The stable limit cycle surrounding the unstable fixed point (represented as a circle) is represented by the blue oriented curve. The thick curve in the left phase portrait represents the typical trajectory associated to the generation of an action potential. The top figures illustrate the typical accompanying electrophysiological responses to step variations of current.

doi: https://doi.org/10.1371/journal.pcbi.1003040.g001