<p>The neocortex is just sight and hearing. You really need to include the entire nervous system's number of nerves to truly appreciate the processing power of the human neural network. How many nerves are in the human body? Even an estimate of 10^11 (100 billion) neurons times an average of 7000 dendrites or 7.0 * 10^4 connections is 7.0 * 10^15 (7,000,000,000,000,000) or 7 quintillion neural connections. Each neuron operates once every 10 ms or 100 times per second, or 700 * 10^15 or 700 quintillion operations per second.</p>

<p>Furthermore, the chemical connection between neurons are effectively "analog", or floating-point, so the correct term isn't "bits per second" but FLOPS. Collectively, my estimate above based on common google searches is 700 exaFLOP per second. For comparison, new the supercomputer being installed at Argonne Labs operates at 1 exaFLOPS and comes with no software.</p>

CC BY-SA 4.0
2019-03-25T19:41:08.557Z
Welcome. We ask answers to be backed up by credible sources, preferably journal papers.
AliceD
CC BY-SA 4.0
2019-03-27T10:22:45.017Z
There are multiple inaccuracies in this answer. The neocortex is not just "sight and hearing", but also taste, touch, smell, motor control, movement planning, speech, and many many more. Neurons don't perform an "operation" 100 times per second, with any meaningful comparison to a CPU's operations. Direct use of FLOPS to measure synaptic computation is also tenuous. Please back up your statements with references.
Dylan Richard Muir
CC BY-SA 4.0
2024-09-01T23:39:04.183Z
An exaflops is 10^18 flops, which is more than 700e15.
Aleksandr Dubinsky
CC BY-SA 4.0
2019-03-20T23:05:01.860Z
2019-03-27T00:01:12.243Z
2019-03-27T00:01:12.243Z
user3422093
<p>The human neocortex contains approximately 1.5x10^14 synapses, connecting its 19–23 billion neurons.</p>

<p>Source: Pakkenberg, B., Pelvig, D., Marner, L., Bundgaard, M. J., Gundersen, H. J. G., Nyengaard, J. R., &amp; Regeur, L. (2003). Aging and the human neocortex. Experimental Gerontology, 38(1-2), 95-99. doi:10.1016/S0531-5565(02)00151-1</p>

CC BY-SA 3.0
2014-08-11T11:04:59.390Z
For the less mathematically inclined, $1.5 \times 10^{14} = 100,000,000,000,000$, or 150 trillion.
Eoin
CC BY-SA 3.0
2014-08-12T11:56:22.003Z
150 000 000 000 000 instead :)
mounaim
CC BY-SA 3.0
2014-08-12T12:08:29.333Z
@Dylan the average number of human brain neurons is 100 billion :) not 19-23. This is what I'm reading everywhere http://www.human-memory.net/brain_neurons.html for exemple
mounaim
CC BY-SA 3.0
2014-08-12T13:35:56.743Z
The numbers in Pakkenberg et al apply to human neocortex, presumably ignoring subcortical structures (plus cerebellum, for instance), which would inflate the numbers somewhat. Also, if you have a solid reference from a research article using stereology, please feel free to include it. The numbers bandied around are usually just orders of magnitude (i.e. accurate to within a multiple of 10).
Dylan Richard Muir
CC BY-SA 3.0
2014-08-30T05:15:55.673Z
[This 2009 paper](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2776484/) estimates the human brain as having 85 billion neurons. [Interesting TED talk about it](http://www.youtube.com/watch?v=_7_XH1CBzGw), too.
Chelonian
CC BY-SA 3.0
2014-08-11T08:14:57.847Z
2014-08-30T12:09:56.693Z
2014-08-30T12:09:56.693Z
Dylan Richard Muir
<p>Knowing there are <strong>100,000,000,000</strong> neurons in an average human brain, and <strong>7,000</strong> dendrites in each neuron, and neurons are connected to each other by dendrites and axon terminals, how many synapses are there in an average human brain? (I don't know how many axon terminals per neuron there are on average.)</p>

CC BY-SA 3.0
2014-08-12T12:02:45.200Z
well this what I learned using this beatiful schema :) http://en.wikipedia.org/wiki/Neuron#mediaviewer/File:Complete_neuron_cell_diagram_en.svg
mounaim
<neuroscience><neuroanatomy>
How many synapses in the average human brain?
mounaim
# How many synapses in the average human brain?

(Asked by: username_0 on 2014-08-08)

Knowing there are **100,000,000,000** neurons in an average human brain, and **7,000** dendrites in each neuron, and neurons are connected to each other by dendrites and axon terminals, how many synapses are there in an average human brain? (I don't know how many axon terminals per neuron there are on average.)

**Tags:** neuroscience, neuroanatomy

> **Comments:**
> **username_0**: well this what I learned using this beatiful schema :) http://en.wikipedia.org/wiki/Neuron#mediaviewer/File:Complete_neuron_cell_diagram_en.svg  

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## 2 answers

### Answer by username_3 on 2014-08-11. Score: 5 | Accepted answer

The human neocortex contains approximately 1.5x10^14 synapses, connecting its 19–23 billion neurons.

Source: Pakkenberg, B., Pelvig, D., Marner, L., Bundgaard, M. J., Gundersen, H. J. G., Nyengaard, J. R., & Regeur, L. (2003). Aging and the human neocortex. Experimental Gerontology, 38(1-2), 95-99. doi:10.1016/S0531-5565(02)00151-1

> **Comments:**
> **username_5**: For the less mathematically inclined, $1.5 \times 10^{14} = 100,000,000,000,000$, or 150 trillion.  
> **username_0**: 150 000 000 000 000 instead :)  
> **username_0**: @Dylan the average number of human brain neurons is 100 billion :) not 19-23. This is what I'm reading everywhere http://www.human-memory.net/brain_neurons.html for exemple  
> **username_3**: The numbers in Pakkenberg et al apply to human neocortex, presumably ignoring subcortical structures (plus cerebellum, for instance), which would inflate the numbers somewhat. Also, if you have a solid reference from a research article using stereology, please feel free to include it. The numbers bandied around are usually just orders of magnitude (i.e. accurate to within a multiple of 10).  
> **username_6**: [This 2009 paper](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2776484/) estimates the human brain as having 85 billion neurons. [Interesting TED talk about it](http://www.youtube.com/watch?v=_7_XH1CBzGw), too.  

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### Answer by username_1 on 2019-03-20. Score: -1

The neocortex is just sight and hearing. You really need to include the entire nervous system's number of nerves to truly appreciate the processing power of the human neural network. How many nerves are in the human body? Even an estimate of 10^11 (100 billion) neurons times an average of 7000 dendrites or 7.0 \* 10^4 connections is 7.0 \* 10^15 (7,000,000,000,000,000) or 7 quintillion neural connections. Each neuron operates once every 10 ms or 100 times per second, or 700 \* 10^15 or 700 quintillion operations per second.

Furthermore, the chemical connection between neurons are effectively "analog", or floating-point, so the correct term isn't "bits per second" but FLOPS. Collectively, my estimate above based on common google searches is 700 exaFLOP per second. For comparison, new the supercomputer being installed at Argonne Labs operates at 1 exaFLOPS and comes with no software.

> **Comments:**
> **username_2**: Welcome. We ask answers to be backed up by credible sources, preferably journal papers.  
> **username_3**: There are multiple inaccuracies in this answer. The neocortex is not just "sight and hearing", but also taste, touch, smell, motor control, movement planning, speech, and many many more. Neurons don't perform an "operation" 100 times per second, with any meaningful comparison to a CPU's operations. Direct use of FLOPS to measure synaptic computation is also tenuous. Please back up your statements with references.  
> **username_4**: An exaflops is 10^18 flops, which is more than 700e15.  

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