Chaotic spiking in the Hodgkin-Huxley nerve model with slow inactivation of the sodium current.

The Hodgkin-Huxley (HH) equations with a modification in which the inactivation process (h variable) of sodium channels is slightly slowed down are investigated. It is shown that this slight modification changes the HH dynamics to a completely different one, with chaotic spiking and very long interspike intervals appearing in a generic manner, although the initiation mechanism of repetitive firing is a simple Hopf bifurcation.