Yes, answer #1. Impossible to calculate, answer #2.

The only way you can count synapses is to do EM and then reconstruct a neuron. It is an arduous process. To actually do it repeatedly in several different neurons in a particular portion of the brain, on a statistically significant number of neurons, is simply not possible, not even with computing. To then compare averages (meaning from a statistically significant number of brains) across brain regions is not doable.

That being said, if you compare brain activity on PET scans, for example, you can demonstrate which parts of the brain are the most active at any particular time, while performing particular tasks. Also, in model systems (transgenic mice, fruit flies) in which synapses can be labeled with GFP, you might be able to count synapses efficiently using software and counting algorithms, but in humans? Not really doable.

Dear Aloisia

Thank you very much for the response.

In recent years Dr. Suzana Herculano-Houzel has been able to obtain the density of neurons in different parts of the brain by using cell membrane dissolution and making a homogeneous mixture of whole soup and then counting the nucleus of cells.

But there seems to be no information about the density of synapses in different parts of the brain.

Dr. Sebastian Seung tries to get a complete pattern of the human brain connectome but the project will take decades.

https://www.ted.com/talks/sebastian_seung

I am looking for a way to count synapses in various brain tissues. Using GFP to count the synapses, attracted my attention to itself. I would be happy if you give me a resource for further reading about this method.

Dear Pooriya,

I haven't kept up with this for a few years so I don't know what the current stateof the art is, but my best recommendations:

The Drosophila brain is the focus of a huge project at Janelia Farms (the intramural HHMIW campus), where Gerry Rubin is spear-heading the movement to track every synapse in the adult fly brain. This is being done using GFP-tagged synaptic proteins and I am attaching a review on the topic.

I believe similar projects are being tackled in the mouse brain via the protein tagging project that Tian Xu tookm on several years ago (tagging every protein in the mouse genome with a genetic fluorescent protein tag). Only in China would maintenance of such a large collection of transgenic mouse be economically feasible. I think it is going on at Fudan University. Tian Xu has faculty appointments at both, Yale University and Fudan University. IF you google him, I am sure you will find the information you need regarding synaptic labeling in the mammalian brain.

Good luck!

Aloisia Schmid

Article Methods to investigate the structure and connectivity of the...

Dear Aloisia

Your advice is so helpful. Thank you very much for your time.

Glad it helped and you are welcome!