Big breakthrough for neuroscience: they have completed the map of an insect’s brain

Brains are interconnected neural networks, and all brains of all species must perform complex behaviors, such as navigating their environment, choosing food, or escaping predators. NOW, A scientific team has succeeded in completing the first map of an insect’s brain.

This representation of the neural wiring of the brain of a fruit fly larva It’s a “historic achievement” for neuroscience, officials say, bringing scientists closer to “true understanding” of the mechanism of thought, opening the door to future brain research and inspiring new ones. architecture of machine learning.

This is the largest complete cerebral connectome – a diagram of neuronal connections – described to date. Details are published in the magazine Science.

Behind this laborious investigation which lasted 12 years there is a team from Johns Hopkins University (USA) and Cambridge (UK).

“If we want to understand who we are and how we think, it is partly understand the mechanism of thoughtsays Joshua T. Vogelstein of Johns Hopkins, for whom the key is how neurons connect to each other.

The first attempt to map a brain – a 14-year roundworm study 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, says Johns Hopkins.

Complete connectomes have only been generated from a few small species of a few hundred or thousands of neurons: roundworms, sea squirt larvae and marine annelid larvae.

“This means that neuroscience has worked for the most part without circuit boards,” summarized Marta Zlatic, from the British university. “Without knowing the structure of a brain, we guess how the calculations are implemented, but Now we can begin to mechanically understand how the brain works.”he explained.

Current technology, he added, is not yet advanced enough to map the connectome of higher animals such as large mammals.

However, “All brains are similar – they are interconnected neural networks – and all brains of all species must perform many complex behaviors: process sensory information, learn, select actions, navigate their environment, choose food, recognize peers, or escape predators.

The connectome of the young fruit fly, ‘Drosophila melanogaster’, is the most complete and extensive map of an insect’s brain. Understand 3,016 neurons and all connections between them: 548,000.

To get a complete cellular-level picture of a brain, it is necessary to divide it into hundreds or thousands of individual tissue samples, all of which must be analyzed under an electron microscope before the laborious process of reconstructing the pieces, neuron by neuron. . , into a complete and accurate portrait of a brain.

The team deliberately chose the larva of the vinegar fly (or fruit fly) because, for an insect, the species shares much of its basic biology with humans, including a comparable genetic basis.

The work lasted 12 years; imaging alone took about a 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 on a map, painstakingly annotating the connections between neurons.

They classified each neuron according to the function it performs and they found, for example, that the most active circuits in the brain were those that went to and from neurons in the learning center.

They have also developed computer tools to identify the possible routes for the flow of information and the different types of circuits.

The work showed circuit characteristics that were “stunningly” reminiscent of machine learning architectures, so the team hopes that continued study can inspire new artificial intelligence systems.

“What we learned about the fruit fly code will have implications for the human code,” Vogelstein said. “That’s what we want to figure out: 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.

The brain of a mouse is estimated to be a million times larger than that of a baby fruit fly, meaning the possibility of mapping it is not likely in the near future.

Still, scientists hope to tackle it, they say, perhaps within the next decade.

(With information from EFE)

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