Researchers at the University of Cambridge have pieced together a map showing every single neuron and how they’re wired together in the brain of a fruit fly larva.


The map shows all 3,016 of the neurons in the larva’s brain and the complex network of 548,000 synapses - known as the connectome - that carry chemical signals between them. It is the biggest map of its kind ever produced.

The team hope that the map will enable them to study how signals travel through the brain and affect learning and behaviour.

“The way the brain circuit is structured influences the computations the brain can do. But, up until this point, we’ve not seen the structure of any brain except of the roundworm Caenorhabditis elegans, the tadpole of a low chordate, and the larva of a marine annelid, all of which have several hundred neurons,” said co-researcher Prof Marta Zlatic of the Medical Research Council Laboratory of Molecular Biology.

“This means neuroscience has been mostly operating without circuit maps. Without knowing the structure of a brain, we’re guessing on the way computations are implemented. But now, we can start gaining a mechanistic understanding of how the brain works.”

The team produced the image by scanning thousands of slices of the larva’s brain using a high-resolution electron microscope and painstakingly marking out the connections between the neurons.

They now plan to delve deeper into the map to study the structures involved with specific functions such as learning and decision-making. Although the current technology isn’t sophisticated enough to map out mammal brains, there is still much to learn from studying the larva brain, the researchers say.

“All brains are similar – they are all networks of interconnected neurons – and all brains of all species have to perform many complex behaviours: they all need to process sensory information, learn, select actions, navigate their environments, choose food, recognise their conspecifics, escape from predators etc,” said Zlatic.

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“In the same way that genes are conserved across the animal kingdom, I think that the basic circuit motifs that implement these fundamental behaviours will also be conserved.”

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Jason Goodyer
Jason GoodyerCommissioning editor, BBC Science Focus

Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.