Figure 7

Computational simulation favors a somatic origin of sequential spikes under the condition of pre-depolarization, and axonal origin for spikes without pre-depolarization. A) A pre-depolarization pulse significantly inactivates axonal VGSCs, including an increase of their threshold by ΔV and a decrease of activation by Δi. B) The number of simulated spikes appears higher at the soma (red trace) than the axon (blue) induced by a long-time step depolarization (black). C) illustrates spike number vs. normalized stimuli at the soma (red triangles) and the axon (blue circles; n = 20, p < 0.01). D) shows the activation curves of somatic VGSCs (red trace) and of axonal ones (blue) by the pulses without pre- depolarization and hyperpolarization. E) The number of simulated spikes appears higher at the axon (blue trace) than the soma (blue) induced by a cosine-wave depolarization pulse (black). F) illustrates input–output curves at axonal spikes (blue circles) and somatic ones (red triangles; n = 20, p < 0.01).