<p>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 <em>balance</em> between excitation and inhibition.  </p>

<p>see:
attalah and scanziani 2009 (experiment) <a href="http://labs.biology.ucsd.edu/scanziani/documents/AtallahNeuron09.pdf" rel="nofollow">http://labs.biology.ucsd.edu/scanziani/documents/AtallahNeuron09.pdf</a></p>

<p>okun and lampl 2008 (experiment)
<a href="http://www.nature.com/neuro/journal/v11/n5/full/nn.2105.html" rel="nofollow">http://www.nature.com/neuro/journal/v11/n5/full/nn.2105.html</a></p>

<p>van vreeswijk and sompolinsky (theory)
<a href="http://www.sciencemag.org/content/274/5293/1724.short" rel="nofollow">http://www.sciencemag.org/content/274/5293/1724.short</a></p>

CC BY-SA 3.0
2015-05-15T06:38:04.293Z
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.
Christian Hummeluhr
CC BY-SA 3.0
2015-05-15T06:39:58.420Z
figure 2c is pretty great for that
honi
CC BY-SA 3.0
2015-05-15T06:50:24.127Z
Wow, it really is. Almost too good ... Methodologist sense tingling!
Christian Hummeluhr
CC BY-SA 3.0
2015-05-15T06:28:52.863Z
2015-05-27T19:47:47.283Z
2015-05-27T19:47:47.283Z
honi
<p>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 <a href="http://en.wikipedia.org/wiki/Chemical_synapse#Synaptic_strength" rel="nofollow">here</a> is a pretty good place to start, or if you want more detail on how that pulls together in an actual system, <a href="http://www.jneurosci.org/content/31/48/17555.full" rel="nofollow">this paper</a> is a good place to start.</p>

CC BY-SA 3.0
2014-09-16T20:45:04.207Z
Thanks for that, the first link certainly gave a rough upper/lower limit and the second link looks very useful.
James
CC BY-SA 3.0
2014-09-16T19:35:22.800Z
2014-09-16T19:35:22.800Z
Krysta
<p>I am looking for a rough estimation of the number of action potentials from other neurons required to cause a neuron to fire?</p>

<p>I read <a href="https://faculty.washington.edu/chudler/ap.html" rel="nofollow">here</a> 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)?</p>

<p><em>I am not a neuroscientist and suspect this question is unanswerable but though this was the place to ask!</em></p>

<neuroscience><theoretical-neuroscience><neural-network>
How many action potentials from presynaptic neurons would be required to make a postsynaptic neuron fire?
James
# How many action potentials from presynaptic neurons would be required to make a postsynaptic neuron fire?

(Asked by: username_0 on 2014-09-16)

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](https://faculty.washington.edu/chudler/ap.html) 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!*

**Tags:** neuroscience, theoretical-neuroscience, neural-network


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## 2 answers

### Answer by username_3 on 2014-09-16. Score: 4 | Accepted answer

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](http://en.wikipedia.org/wiki/Chemical_synapse#Synaptic_strength) is a pretty good place to start, or if you want more detail on how that pulls together in an actual system, [this paper](http://www.jneurosci.org/content/31/48/17555.full) is a good place to start.

> **Comments:**
> **username_0**: Thanks for that, the first link certainly gave a rough upper/lower limit and the second link looks very useful.  

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### Answer by username_1 on 2015-05-15. Score: 5

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>

> **Comments:**
> **username_2**: 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.  
> **username_1**: figure 2c is pretty great for that  
> **username_2**: Wow, it really is. Almost too good ... Methodologist sense tingling!  

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