In Izhikevich's Dynamical Systems in Neuroscience, p. 199, one learns about a class of neurons that can be forced to fire with maximal frequency:

enter image description here

Injecting a constant current of appropriate size (here: 320pA) a neuron of this class can be forced to fire with maximal frequency. The frequency is determined by the refractory period of the ion channels producing the action potential.

What the picture does not show is what happens beyond the half-of-a-second that is recorded and displayed: Will the neuron continue to fire with maximal frequency forever, as long as the input current is applied? I guess eventually it gets exhausted and must pause or lower its frequency.

My questions:

  1. General: For which injected currents can the neuron continue to fire with the corresponding frequency forever? Beyond which current $I_{critical}$ does it have to make a pause or lower the frequency?

  2. Qualitative: Beyond $I_{critical}$, does it make a pause or does it lower its frequency? Or both?

  3. Quantitative: If it makes a pause, when and how long is it? (This could be called its "secondary refractory period".) If it lowers its frequency, when does it start (to lower its frequency) and by which rate?

  • $\begingroup$ Your picture shows tonic firing, not bursting; tonic firing is sort of the opposite of bursting. Try a Google Images search for "neuron burst firing" or something similar. $\endgroup$ – Bryan Krause Nov 20 '17 at 16:53
  • $\begingroup$ Burst firing is due to intrinsic properties of some neurons that cause them to fire >1 action potentials in a group. Maximal tonic firing is just the maximum firing rate of a cell given a constant depolarizing current. $\endgroup$ – Bryan Krause Nov 20 '17 at 16:57
  • $\begingroup$ Bursting!=maximally firing - those are not the same things. Have you tried a google image search for "neuron burst firing" to see how that is clearly different from the activity you show here? $\endgroup$ – Bryan Krause Nov 20 '17 at 17:09
  • $\begingroup$ Let us continue this discussion in chat. $\endgroup$ – Hans-Peter Stricker Nov 20 '17 at 18:42
  • $\begingroup$ I removed any mentions of "bursting". $\endgroup$ – Hans-Peter Stricker Nov 20 '17 at 22:19

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