Neurophysiology: Hodgkin and Huxley model--still standing?

Action potentials in cortical neurons show a variable threshold and a sudden rise in membrane potential at initiation. Naundorf et al. fail to explain these features using single- or double-compartment Hodgkin-Huxley-style models, suggesting instead that they could arise from cooperative opening of Na+ channels, although there is no direct biological evidence to support this. Here we show that these so-called unique features are to be expected from Hodgkin-Huxley models if the spatial geometry and spike initiation properties of cortical neurons are taken into account--it is therefore unnecessary to invoke exotic channel-gating properties as an explanation.