Sciences map the inner workings of a fruit fly’s brain

Scientists have created the first map of every neuron in an adult fly brain.

The research team says this first wiring diagram of the complete brain of a fruit fly yields new insights into the brain connections that control a fly’s sensory perceptions, memory and even mating rituals.

“The closer you look, the more surprised we as scientists are,” said Gregory Jefferis, a neuroscientist at the University of Cambridge and one of the co-leaders of the research.

“If we want to understand how the brain works, we need a mechanistic understanding of how all the neurons fit together and let you think. For most brains we have no idea how these networks function,” Jefferis added in a statement. 

“Flies can do all kinds of complicated things like walk, fly, navigate, and the males sing to the females. Brain wiring diagrams are a first step towards understanding everything we’re interested in – how we control our movement, answer the telephone, or recognise a friend,” he added.

The 3D models were made from the brain of a dead fly sliced into 7,000 separate 40 nanometre sections, using high-resolution electron microscopy. A whole fly brain is less than one millimetre wide.

Researchers say looking into a dead fly’s brain helped them discover substantial similarities with previous smaller-scale samples of a fly brain and come to the conclusion that each brain isn’t a unique structure.

The researchers analysed 100 terabytes (TB) of images, around 100 laptops worth of memory, to map to the 140,000 neurons and over 50 million connections.

AI helped to process the imaged sections because it would have taken 4,000 human years to produce otherwise, according to the team.

The researchers also had more than 280 researchers around the world help to proofread the data.

“This brain map, the biggest so far, has only been possible thanks to technical advances that didn’t seem possible ten years ago. It is a true testament to the way that innovation can drive research forward,” said Marta Costa, a researcher from the University of Cambridge.

‘First step’ to better understanding the brain

The researchers say the whole fly brain map is a key first step to completing larger brains.

“In the future, we hope that it will be possible to compare what happens when things go wrong in our brains, for example in mental health conditions,” said Mala Murthy, one of the co-leaders of the research at Princeton University.

The entire database is freely available to all researchers in hopes of better understanding how a healthy brain works.

However, producing a wiring diagram of a human brain will not happen anytime soon.

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A human brain is many times more complicated than the brain of a fruit fly and we are a long way from being able to attempt this feat.

“There’s a million-fold difference in neurons between the fly brain and the human brain. And in fact, the volume of their brains, which is quite important for imaging and image processing to generate these brain maps is even a little bit bigger,” Jefferis said.

Work is already being considered on much smaller mammals – like mice.

For more on this story, watch the video in the media player above.

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Video editor • Roselyne Min