The first full 3D map of a real brain, a historical milestone that brings researchers closer to understanding the mechanism by which thought occurs, is already a reality. An international team led by the universities of Cambridge and Johns Hopkins has developed a model that carefully reproduces every neural connection in the brain of a fruit fly larva. This insect is considered archetypal due to its similarities with the human organism.
“If we want to understand how we think and what makes us who we are, it’s about understanding the mechanism by which ideas are generated,” says Joshua T. Vogelstein, a biomedical engineer specializing in connectomics, the science of connections in the nervous system. As he explains, the researchers hope to inspire with the article that post today Science new research on architectures machine learning applied to medical biology. “The key is to know how neurons connect to each other“.
The first project to map a brain, that of a nematode wormtook fourteen years and was rewarded for the Nobel Prize in Physiology and Medicine for Sydney Brenner, John Sulston, and Bob Horvitz in 2002. Partial connectomes of the nervous system of flies, mice, and even Humans. But they only involve a tiny fraction of the brain: the largest range from a hundred to a thousand neurons, like those of a larval annelid marine worm or a sea squirt.
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In contrast, the connectome of the larva of Drosophila melanogaster It is not only the largest, but also the most complex on record. He insect has 3,016 neurons, which add up to 548,000 connections between them. “50 years have passed, and this is the first connectome of a brain that we have. All the previous work has led us here,” says Vogelstein. The work, he qualifies, has been extremely complex even with the most modern technology. Ha born 12 yearscalculating a whole day to produce the image of each one of the neurons.
The connectome of neural relations of the larval brain. Johns Hopkins University/University of Cambridge
The team chose the fruit fly because shares a significant part of its fundamental biology with humans, including a comparable genetic base. It is also a useful model for neurology because of the insect’s extensive capacity to learn and make decisions to modify its behavior. From a practical point of view, finally, your brain is sufficiently compact enough to study it and put it back together in a “reasonable” time, according to the authors. Thus, to trace the model at the cellular level, it is essential to slice it into hundreds of thousands of cellular tissue samples, from which an image is extracted using an electron microscope. After that will come the work of rebuild it neuron by neuron.
The Cambridge team generated the high-resolution images of the brain, and manually analyzed them to detect both individual neurons and the synaptic connection between them. Using these data, the Johns Hopkins scientists analyzed brain connectivity for more than three years. Using techniques based on shared connectivity patterns, they were able to locate clusters of neurons and looked at how information can spread through the brain. Thus, they identified the regions with the most activity, those that led to the learning Center and those who abandoned it.
These methods developed for the work are valid for any other neurological project, and their code is available for those who want to try it with the mouse brain, a million times bigger than that of the larva. “What we have learned about the fruit fly code has implications for humans,” explains Vogelstein. “That’s what we want to understand: how write a program that makes a human brain system work“. However, the authors recall that they have taken more than a decade with a simple brain. The map of ours, they warn, may be “out of reach” of science in the short term.
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