<p><strong>Note: this answer is imprecise; read its comments below.</strong></p>
<p>&quot;...based on the Hodgkin–Huxley model calculates by the method of ion counting and power integration that an action potential consumes 2.468 × 10−7 J of biological energy produced by the hydrolysis of Adenosine triphosphate (ATP)...&quot; (ref. <a href="https://link.springer.com/article/10.1007/s11571-018-9503-3" rel="nofollow noreferrer">https://link.springer.com/article/10.1007/s11571-018-9503-3</a>)</p>
<p>Supposing we have 100 billion neurons in the brain, the total energy consumed would be:</p>
<p>1E11 * 2.468E-7 J = 2.468E4 J</p>
<p>So 24KJ to generate a single action potential for each neuron of the brain.</p>
<p>To lift an apple 1 meter requires roughly 1 J. So the energy needed to make each single neuron fire once would be enough to lift 24 thousand apples 1 meter, all at the same time.</p>
<p>So that is why it is impossible: the brain would catch fire. An we would starve.</p>

CC BY-SA 4.0
2022-12-21T16:06:22.770Z
Few things wrong with this answer... First of all, action potentials are almost entirely passive. They are powered by pre-existing electrical gradients; yes, it takes energy to maintain those gradients over the long run, but this maintenance occurs over seconds to minutes; the precise timing of a spike doesn't matter. Further, all neurons of the brain are spiking all the time, some might be as slow as 1 Hz but others as fast as 100 Hz. There's no additional energy expenditure for every neuron of the brain to fire at once within, say, a second, versus firing at once within, say, 1 ms.
Bryan Krause
CC BY-SA 4.0
2022-12-21T16:07:50.480Z
Lastly, the HH model is based on the giant squid; humans don't have giant squid neurons, we have human neurons, and mammalian neurons have some very important modifications like voltage-gated potassium channels that greatly minimize the metabolic costs of single action potentials by limiting the counter-currents during the rising phase of the action potential.
Bryan Krause
CC BY-SA 4.0
2022-12-21T16:46:47.420Z
@BryanKrause - Thank you for your constructive comments, and I would like to read a correct answer from you. From what you wrote, each neuron still needs/dissipates some amount of energy when firing (either during the spike process of before that). How much is that?
Pietro
CC BY-SA 4.0
2022-12-21T16:58:09.417Z
This paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4189373/ references another that estimates 0.66 J released per minute per gram of brain tissue. Most metabolic activity in the brain is synaptic currents rather than action potentials - action potentials are inexpensive energetically: what's metabolically expensive is when lots of ions move across membranes. Very few ions need to move for an AP; lots of ions move when you have competing excitatory and inhibitory conductances. I don't know what the ratio is or what you'd estimate a single spike to cost, though.
Bryan Krause
CC BY-SA 4.0
2022-12-21T14:11:11.913Z
2022-12-22T16:05:34.833Z
2022-12-22T16:05:34.833Z
Pietro
<p>I'm trying to find a paper that states otherwise -- that we can't have all neurons fire simultaneously, but all I can find is Quora questions (<a href="https://www.quora.com/What-would-result-if-all-the-brains-synapses-fired-continuously" rel="nofollow noreferrer">like this</a>) which mentions that if all neurons will fire together we will have a seizure.</p>

CC BY-SA 4.0
2022-12-19T05:22:51.400Z
What does "simultaneously" mean? What's the purpose of the question/what will it help you accomplish or understand?
Bryan Krause
CC BY-SA 4.0
2022-12-19T05:35:50.357Z
"simultaneously" means at the same time. I assume that all neurons are being used in general at some point, but my question is, can there be a given time when they are all active at the same time.  The link I shared from Quora states that there isn't such time, as this will result in a seizure. I'm trying to find a publishable paper that states the same (or the opposite).
Penguin
CC BY-SA 4.0
2022-12-19T05:54:07.623Z
But why does it matter if they can or not? In principle, nothing prevents it, but also it would just never happen, so I don't see any purpose in asking the question.
Bryan Krause
CC BY-SA 4.0
2022-12-19T06:00:34.553Z
If they don't it raises some interesting ideas from a computational side. I'm writing a paper and need to ensure that the ideas are based on a real phenomena (and not an assumption). But I do understand your reasoning and appreciate the help on this!
Penguin
CC BY-SA 4.0
2022-12-19T14:48:13.640Z
Why does it raise interesting ideas from a computational side? Imagine, if neurons are firing at 100Hz (very fast, unusually fast for neurons, but it'll help us get to simultaneity), and you consider firing within a 1 ms window to be simultaneous (which isn't actually simultaneous, which is why I asked "what does simultaneously mean?"), the chance of all N neurons firing at the same time is equal to 1/0.1^N - you'll see that once you have a few neurons, this chance is very small, let alone 10s of billions. Nothing interesting there, just simple probability.
Bryan Krause
<brain><cell-signaling>
Can all neurons fire at the same time?
Penguin
# Can all neurons fire at the same time?

(Asked by: username_0 on 2022-12-19)

I'm trying to find a paper that states otherwise -- that we can't have all neurons fire simultaneously, but all I can find is Quora questions ([like this](https://www.quora.com/What-would-result-if-all-the-brains-synapses-fired-continuously)) which mentions that if all neurons will fire together we will have a seizure.

**Tags:** brain, cell-signaling

> **Comments:**
> **username_1**: What does "simultaneously" mean? What's the purpose of the question/what will it help you accomplish or understand?  
> **username_0**: "simultaneously" means at the same time. I assume that all neurons are being used in general at some point, but my question is, can there be a given time when they are all active at the same time.  The link I shared from Quora states that there isn't such time, as this will result in a seizure. I'm trying to find a publishable paper that states the same (or the opposite).  
> **username_1**: But why does it matter if they can or not? In principle, nothing prevents it, but also it would just never happen, so I don't see any purpose in asking the question.  
> **username_0**: If they don't it raises some interesting ideas from a computational side. I'm writing a paper and need to ensure that the ideas are based on a real phenomena (and not an assumption). But I do understand your reasoning and appreciate the help on this!  
> **username_1**: Why does it raise interesting ideas from a computational side? Imagine, if neurons are firing at 100Hz (very fast, unusually fast for neurons, but it'll help us get to simultaneity), and you consider firing within a 1 ms window to be simultaneous (which isn't actually simultaneous, which is why I asked "what does simultaneously mean?"), the chance of all N neurons firing at the same time is equal to 1/0.1^N - you'll see that once you have a few neurons, this chance is very small, let alone 10s of billions. Nothing interesting there, just simple probability.  

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## 1 answers

### Answer by username_2 on 2022-12-21. Score: -1

**Note: this answer is imprecise; read its comments below.**

"...based on the Hodgkin–Huxley model calculates by the method of ion counting and power integration that an action potential consumes 2.468 × 10−7 J of biological energy produced by the hydrolysis of Adenosine triphosphate (ATP)..." (ref. <https://link.springer.com/article/10.1007/s11571-018-9503-3>)

Supposing we have 100 billion neurons in the brain, the total energy consumed would be:

1E11 \* 2.468E-7 J = 2.468E4 J

So 24KJ to generate a single action potential for each neuron of the brain.

To lift an apple 1 meter requires roughly 1 J. So the energy needed to make each single neuron fire once would be enough to lift 24 thousand apples 1 meter, all at the same time.

So that is why it is impossible: the brain would catch fire. An we would starve.

> **Comments:**
> **username_1**: Few things wrong with this answer... First of all, action potentials are almost entirely passive. They are powered by pre-existing electrical gradients; yes, it takes energy to maintain those gradients over the long run, but this maintenance occurs over seconds to minutes; the precise timing of a spike doesn't matter. Further, all neurons of the brain are spiking all the time, some might be as slow as 1 Hz but others as fast as 100 Hz. There's no additional energy expenditure for every neuron of the brain to fire at once within, say, a second, versus firing at once within, say, 1 ms.  
> **username_1**: Lastly, the HH model is based on the giant squid; humans don't have giant squid neurons, we have human neurons, and mammalian neurons have some very important modifications like voltage-gated potassium channels that greatly minimize the metabolic costs of single action potentials by limiting the counter-currents during the rising phase of the action potential.  
> **username_2**: @BryanKrause - Thank you for your constructive comments, and I would like to read a correct answer from you. From what you wrote, each neuron still needs/dissipates some amount of energy when firing (either during the spike process of before that). How much is that?  
> **username_1**: This paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4189373/ references another that estimates 0.66 J released per minute per gram of brain tissue. Most metabolic activity in the brain is synaptic currents rather than action potentials - action potentials are inexpensive energetically: what's metabolically expensive is when lots of ions move across membranes. Very few ions need to move for an AP; lots of ions move when you have competing excitatory and inhibitory conductances. I don't know what the ratio is or what you'd estimate a single spike to cost, though.  

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