An international team of researchers has mapped the ‘wiring’ of the entire brain of an insect, a fruit fly larva (Drosophila melanogaster). Called connectome, shows in detail how the neurons are connected to each other, in the same way that a road map indicates which are the highways, the main ones and the minor ones. The work, published in the magazine ‘Science’, can help to understand the human behavior and learninghow diseases develop Alzheimer’s and Parkinson’s and create new artificial intelligence systems.
The first attempt to map a brain, that of the roundworm, was carried out in the 1979s. The effort yielded a Nobel Prize, but it was partial. Since then, partial connectomes of flies, mice and even humans have been mapped, but equally these reconstructions represented only a small fraction of the total brain. Whole connectomes were generated from several small species with a few hundred to a few thousand neurons: a roundworm, a sea squirt larva (a simple marine creature that filters water at the bottom of the ocean), and a sea squirt larva. worm.
The new map goes much further: it includes 3,016 neurons that establish more than half a million contacts, making it the most complete and extensive map ever achieved. It hasn’t been easy, even with the best of modern technology. Getting a complete picture of a brain at the cellular level requires cutting it into hundreds or thousands of individual tissue samples, all of which must be captured with electron microscopes before the painstaking process of reconstructing all those pieces, neuron by neuroninto a complete and accurate picture.
One day per neuron
The work took him to Cambridge University and Johns Hopkins for twelve years. Imaging alone took about a day per neuron. The Cambridge researchers created the high-resolution images of the brain and manually studied them to find individual neurons, rigorously tracking each one and linking its synaptic connections.
Cambridge turned the data over to Johns Hopkins, where the team spent more than three years analyzing how information might spread through the brain. In the end, both groups recorded each neuron and each connection and classified each neuron according to the role it plays in the brain. Google was involved in creating the artificial intelligence algorithms to reconstruct everything that was found. They found that the most active circuits they were the ones that entered and left the neurons of the learning center.
The team deliberately chose the fruit fly larva because, despite being an insect, the species shares much of its fundamental biology with humans, including a comparable genetic background. It also has rich learning and decision-making behaviors, making it a useful model organism in neuroscience.
Joshua T. Vogelstein, lead author of the study and a biomedical engineer at Johns Hopkins, believes that what we’ve learned about the fly code will have implications for understanding our own brains. “If we want to understand who we are and how we think, part of it is understanding the mechanism of thought,” he says. And the key to that is knowing how neurons connect to each other.” The results could help to understand the mechanisms of how we behave, make decisions or learn and could lead to future therapeutic interventions.
Furthermore, the map showed circuit features that are impressively reminiscent of powerful machine learning architectures, so the team hopes that continued study will reveal even more computational principles and may inspire new AI systems.
“The study is spectacular,” Javier Morante, a senior CSIC scientist at the Instituto de Neurosciences in Alicante, who was not involved in it, told this paper. «It’s like a road map of a country, with highways, secondary roads, shortcuts… and such a high resolution that it allows you to see which is the direction of these roads, if they go from the periphery to the center, or vice versa. And with such brutal detail that they delimited, so to speak, the tolls, the petrol stations… Until now, nothing similar had been achieved».
For him, the work will also help us to understand the diseases of the human brain. «The fly is the best animal that can be genetically manipulated. If we understand how this healthy brain is organized, in the future we will be able to manipulate these ‘highways’ and see how this influences behavior, understand the circuits of pathologies such as Parkinson’s or Alzheimer’s”, points out Morante.
The methods developed by the researchers are applicable to any brain-wiring project, and their code is available to anyone trying to map an even larger animal brain. Other teams are already working on a map of the adult fruit fly brain.
Although it is extremely complex, the researchers believe that the brain of a mouse, a million times larger than that of a fly larva, could be mapped within the next decade. Of course, the possibility of doing it with something similar to a human brain “It’s not likely in the near future, maybe not even in our lifetimes.”