Drosophila connectome
It took 12 years, 250 people and $40 million to create a section of the drosophila brain map
Yekaterina_t, Madrobots company blog, Habr
Fruit flies, or fruit flies, are an excellent material for research. Simply because they reproduce very quickly, giving offspring, and evolutionary changes can be tracked over weeks, not months or years.
These flies were also useful to scientists who study the brain. Since the ganglion of these insects is small, it can be scanned without any problems. The other day, scientists from Janelia Research Campus published the result of their 12-year work – a drosophila brain map, the most detailed at the moment.
Article by Xu et al. A Connectome of the Adult Drosophila Central Brain is published on the bioRxiv – VM preprint site.
Janelia Research Campus is part of the Howard Hughes Medical Institute. The university team spent 12 years and $40 million dollars to map the brain of a tiny fly. This is 25 thousand neurons and about 20 million connections between them. And even this is not the whole brain, but only a third of it, although the most important. It houses various organoids responsible for memory, navigation and learning.
According to the researchers, the brain connectome (this is a map of an organ with all the connections between them) will become one of the basic resources for neurosurgeons and scientists who study the nervous system of insects and other living beings. Decoding the brain of a small fly allows you to judge the work of individual organoids, how connections are arranged and in general how the brain works.
From simple to complex – this is how scientists act now. Modern technologies still do not allow us to create any detailed connectome of the human brain, so the brain of much simpler creatures is being studied. By the way, the first living organism whose brain was "decoded" was a nematode. Its nerve node consists of only 302 neurons with 7 thousand connections between them. Even this was an extremely difficult job for 1986.
Gradually, specialists are getting more and more information about the work of the brain of animals and humans. But one of the most important tasks is the compilation of a connectome. This is as important a job as decoding DNA. The compilation of a connectome makes it possible to track the interaction of individual cells and their organelles.
In 2004, a technique was developed for analyzing images of neurons obtained by an electron microscope. This was a serious achievement, which significantly accelerated the "decoding" of the brain. But even in this case, the drosophila brain required the efforts of 250 people – that's how many scientists worked on this project for 12 years.
All this time, the methodology has been improved and refined. As a result, it turned out that the images obtained by an electron microscope were transformed into a three-dimensional map of the brain. The drosophila brain had to be cut into thin plates 20 nm thick to get images of neurons. It was them who were photographed.
After neural networks appeared, scientists used them to compile three-dimensional maps of brain regions with tracking connections between individual cells. But the computer cannot do all the necessary work – scientists need to participate here, both to check the operation of the machine and to perform "manual" tasks that the computer is not yet able to cope with.
The scientists were helped by developers from Google, who created the analysis systems needed by specialists. The final result turned out to be extremely voluminous – the data array "weighs" about 100 gigabytes.
Other scientists who create connectomes also cooperate with Google. For example, as part of a project to study the brain of songbirds. By itself, the brain of birds is very complex, so connectomes are unlikely to appear in the near foreseeable future. Scientists are studying certain aspects of work and areas of the brain – for example, those responsible for memorizing songs. In addition, a section of the mouse brain with a cubic millimeter volume was previously analyzed.
As for the specialists who make up the drosophila brain connectomes, they continue to work. Their goal is to compile a complete connectome of the brain of a fruit fly – both male and female. A budget of $5 million has been allocated for this.
If you decode the mouse brain, then, according to scientists, it will take over half a billion US dollars and even more time.
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