They complete for the first time the map of an insect brain and its neural connections

Brains are networks of interconnected neurons, and all brains in all species have to perform complex behaviors, such as navigating their environment, choosing food, or escaping from predators. Now a science team Has got complete the first brain map of an insect.

This representation of neural wiring of the brain of a fly larva of vinegar is, according to those responsible, a “landmark achievement” for neurosciencewhich brings scientists closer to “the true understanding” of the mechanism of thought, opens the door to future research on the brain and will inspire new machine learning architectures.

It is the largest complete brain connectome –diagram of neural connections– described to date. Details are published in the magazine ‘science’. Behind this painstaking research that lasted 12 years is a team from Johns Hopkins University (United States) and Cambridge (United Kingdom).

“If we want to understand who we are and how we think, part of it is understanding the mechanism of thought,” says Joshua T. Vogelstein of Johns Hopkins, for whom the key is knowing how neurons connect to each other.

The first attempt to map a brain – a 14-year study of the roundworm begun in the 1970s – resulted in a partial map and a Nobel Prize. Since then, partial connectomes have been mapped in many systems, including flies, mice, and even humans, but these reconstructions often represent only a small fraction of the total brain, explains Johns Hopkins.

Complete connectomes have only been generated from several small species with a few hundred or thousands of neurons: roundworm, sea squirt larva, and marine annelid larva. “This means that neuroscience has worked for the most part without circuit maps,” summarizes Marta Zlatic, from the British university. “Without knowing the structure of a brain, we are guessing how the computations are implemented, but now we can begin to understand mechanically how the brain works“, Explain.

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Current technology, he adds, is not yet advanced enough to map the connectome of higher animals such as large mammals. However, “all brains are similar – they are networks of interconnected neurons – and all brains in all species have to perform many complex behaviors: processing sensory information, learning, selecting actions, navigating their environment, choosing food, recognizing their congeners or escape from predators”.

This is the brain map of the vinegar fly

The connectome of the young fruit fly, “Drosophila melanogaster”, is the most complete and extensive map of an insect brain. It includes 3,016 neurons and all the connections between them: 548,000.

To get a complete picture at the cellular level of a brain, it is necessary to divide it into hundreds or thousands of individual tissue samples, all of which have to be analyzed with electron microscopes before the laborious process of reconstructing the pieces, neuron by neuron, into a portrait. complete and precise of a brain.

The team purposely chose the fruit fly larva (or the fruit) because, for an insect, the species shares much of its fundamental biology with humansincluding a comparable genetic base.

The work lasted 12 years; imaging alone took approximately one day per neuron. The researchers scanned thousands of slices of the larva’s brain using a high-resolution electron microscope and reconstructed the resulting images into a map, painstakingly annotating the connections between neurons.

They classified each neuron by the function it performs and found, for example, that the most active circuits in the brain were those that went to and from the neurons in the learning center. They also developed computer tools to identify possible information flow paths and different types of circuits.

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The work showed circuit characteristics that were “strikingly” reminiscent of machine learning architectures, so the team hopes that continued study could inspire new AI systems. “What we have learned about the fruit fly code will have implications for the human code,” says Vogelstein. “That’s what we want to understand: how to write a program that drives a human brain network.”

The methods and codes developed here are available to anyone attempting to map an even larger animal brain. It is estimated that the brain of a mouse is a million times larger than that of a baby fruit fly, which means that the possibility of mapping it is not likely in the near future. Still, scientists hope to deal with it, they say, possibly in the next decade.

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