This Map of Every Neuron in an Adult Fly Brain Could Be Nobel Prize Worthy

It's an accomplishment that scientists have dreamed about for more than half a century. At last, a massive international team of researchers has mapped in exquisite detail every neuron in the brain of an adult animal with eyes and legs.

3D rendering of all ~140k neurons in the fruit fly brain. (FlyWire.ai; Rendering by Philipp Schlegel/University of Cambridge/MRC LMB)

he nifty noggin, which anyone can now freely peruse, is no larger than a poppy seed, and yet it contains 139,255 neurons and 50 million connections.

It belongs to an adult female fruit fly (Drosophila melanogaster).

This might seem like a small victory compared to a human brain, which contains 80 billion neurons and 100 trillion connections, but it's a huge leap from where neuroscientists started in the 1960s.

If history is anything to go by, the research could be in the running for a future Nobel prize.

"This is a major achievement," says neuroscientist Mala Murthy from Princeton University, who helped lead the team.

"There is no other full brain connectome for an adult animal of this complexity."

The only other map that comes close is a 3D diagram of the adult fly 'hemibrain', but it includes only around 20,000 neurons.

Emory University biologist Anita Devineni, who was not involved in the current research, predicts this new map will "transform Drosophila neuroscience" in an accompanying commentary in Nature.

Scientists first started mapping the wiring of animal brains roughly half a century ago, and these initial attempts were focused on a very simple creature: the sightless and legless worm, Caenorhabditis elegans.

In 2002, the scientists behind this partial brain map of just 302 neurons shared a Nobel Prize.

Today, the same feat, which once took over 12 years to complete, takes less than a month.

In 2023, researchers completed a much larger brain map, including all 3,016 neurons in the larva of a fruit fly.

Once again, however, this animal could not walk or see.

An adult fruit fly is the next big step. Its brain networks, which underlie sight and the complicated movements of walking, are similar to those in humans, and they can now be explored in greater detail than ever before.

Neurons from the fruit fly's auditory circuits. (Princeton University)

"Flies can do all kinds of complicated things like walk, fly, navigate, and the males sing to the females," explains molecular biologist Gregory Jefferis from the University of Cambridge, who helped lead the research.

"Brain wiring diagrams are a first step towards understanding everything we're interested in – how we control our movement, answer the telephone, or recognize a friend."

The team that put this diagram together included researchers from 122 institutions, with major contributions from Princeton University, the University of Cambridge, and the University of Vermont.

The map required more than 7,000 slices of a female fruit fly brain and 21 million images, which could have filled 100 typical laptops with their data.