I am looking for a rough estimation of the number of action potentials from other neurons required to cause a neuron to fire?

I read here that a potential of ~ -55mv must be reached before an action potential is fired in a neuron, my thought is how many action potentials from other cells would (roughly) be required to reach this - and in what required time (if it matters)?

I am not a neuroscientist and suspect this question is unanswerable but though this was the place to ask!


2 Answers 2


It is highly variable, depending on the strength and placement of the synapse (which in turn depends on synapse activity and how often the two neurons fire together, among other things). The wikipedia page here is a pretty good place to start, or if you want more detail on how that pulls together in an actual system, this paper is a good place to start.

  • $\begingroup$ Thanks for that, the first link certainly gave a rough upper/lower limit and the second link looks very useful. $\endgroup$
    – James
    Commented Sep 16, 2014 at 20:45

It is very very important to note that in the brain, most neurons are receiving input from way more excitatory synapses than necessary to bring the neuron to threshold. The thing is that they are also receiving input from a huge number of inhibitory synapses as well. This means that it is not how many inputs that are active at a given time that determines whether a neuron fires or not, it is the balance between excitation and inhibition.

see: attalah and scanziani 2009 (experiment) http://labs.biology.ucsd.edu/scanziani/documents/AtallahNeuron09.pdf

okun and lampl 2008 (experiment) http://www.nature.com/neuro/journal/v11/n5/full/nn.2105.html

van vreeswijk and sompolinsky (theory) http://www.sciencemag.org/content/274/5293/1724.short

  • $\begingroup$ Good addition, and nice illustration of inhibition in the brain with the Attalah and Scanziani paper. May use that next time I have to explain it. $\endgroup$ Commented May 15, 2015 at 6:38
  • 1
    $\begingroup$ figure 2c is pretty great for that $\endgroup$
    – honi
    Commented May 15, 2015 at 6:39
  • $\begingroup$ Wow, it really is. Almost too good ... Methodologist sense tingling! $\endgroup$ Commented May 15, 2015 at 6:50

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