Small brain, big deal: Drosophila blueprint could change neuroscience neurology

Researchers have produced the first wiring diagram of an entire fruit fly brain, a breakthrough that promises to revolutionize the field of neuroscience and pave the way for unprecedented insights into how the brain produces behavior.

Rarely has so much effort in science been directed toward so little material, and it took scientists years to map the meanderings of all 139,255 neurons and 50 meters of connections packed inside a fly's poppy-seed-sized brain.

In the process, the researchers classified more than 8,400 different cell types, representing the first complete list of the parts needed to build a fly's brain.

“You might wonder why we should care about the fruit fly brain,” says Sebastian Seung, a professor of computer science and neuroscience at Princeton University and co-leader of the research team. Flywire project. “My simple answer is that if we can truly understand how any brain works, it will inevitably tell us something about all brains.”

The complex tangle of neurons, which if unraveled would reach 150 metres, was mapped out through a painstaking process that began by slicing the brain of a female fruit fly into 7,000 thin slices. Each section was imaged with an electron microscope to reveal structures as small as four millionths of a millimeter across.

The researchers then turned to artificial intelligence (AI) to analyze millions of images and trace the path of every neural and synaptic connection throughout the tiny organ. Because the AI ​​made so many mistakes, a global army of scientists and volunteers was recruited to help correct the errors and finalize the map.

The work has already paid off. Armed with the blueprint, the researchers discovered “afferent” neurons that appear to collect various types of information, and “anchors” that may send signals to coordinate activity across different neural circuits. A specific neural circuit has also been observed that, when stimulated, causes fruit flies to stop in their tracks while walking.

In preparation for what is to come, the researchers used a wiring diagram, known as a neural network, to build a computer simulation of part of the fly's brain. Their simulation experiments led them to identify the neural circuits used to process taste, suggesting that future simulations could shed more light on how brain wiring leads to animal behavior.

“Communication technologies are the beginning of the digital transformation of neuroscience,” Seong said. “This transformation will extend to brain simulation.” “This will be a rapid acceleration of the way we do neuroscience.”

Details of the project, which involved researchers from Canada, Germany, the MRC Laboratory of Molecular Biology and the University of Cambridge in the UK, have been published online. Nine leaves in nature. In an accompanying article, Dr. Anita Devineni, a neuroscientist at Emory University in Atlanta, called the wiring diagram a “landmark achievement.”

Work has already begun to produce a complete wiring diagram of the mouse brain, which researchers hope to complete within five to ten years. But replicating this feat on an entire human brain, with its 86 billion neurons and trillions of connections, is another question. The human brain is approximately a million times more complex than that of a fruit fly, putting a complete wiring diagram beyond practical reach with today's technology. It would also require some massive memory: Scientists estimate it would amount to a zettabyte of data, the equivalent of all the world's Internet traffic for a year.

A more realistic approach is to map the neural connections in parts of the human brain, research that could eventually shed light on whether misconnections underpin neuropsychiatric and other brain disorders. “We simply can't fix what we don't understand, and that's basically why we believe this is an important moment today,” said Dr. John Ngai, director of the US National Institutes of Health's Brain Initiative.

“Clearly we have a big task ahead of us.”