In some ways, fruit flies are like us. They have eyes, legs, a nervous system, and they love fruit. But unlike ours, their brains have only a few thousand neurons. That means scientists can map not just every cell, but every connection between them. , Come to think of it, it’s basically human.
Although I may be exaggerating the similarities to the fruit fly commonly referred to by the scientific name Drosophila (Drosophila melanogaster, Drosophila melanogaster, that part is usually not needed), the use of Drosophila in many biological experiments there is a reason. You may not think you look like one of these creatures, but it definitely looks more like a fruit fly than a bacterium or dinoflagellate. Understanding even relatively simple animals like fruit flies can teach us a lot about animals and life in general.
Despite being perhaps the best-understood organism, along with yeast, a single fruit fly is still orders of magnitude too complex to simulate all its aspects. Hell, I’m having trouble simulating a single cell properly. However, if we consider living things not as gestalts but as collections of interconnected systems, we can start biting with elephants.
The latest bite by a team led by biologists at the University of Cambridge is a “synapse-by-synapse map” of the larval fruit fly brain. With 3,016 neurons and her 548,000 synapses, this complexity is ten times that of the last living creature to map the brain, a member of Congress. (Actually, it was one of the worst types of worms, annelids. Humans have about 86 billion neurons and nearly infinite numbers of synapses.)
Of course, Drosophila larvae are not flies, but they are already sophisticated creatures with adaptive behavior, structures similar to adult fly brains, short- and long-term memory, and other expected brain functions. In addition, they are easier to catch. More importantly, “a compact brain with thousands of neurons that can be imaged at the nanoscale using electron microscopy (EM) and whose circuits can be reconstructed within a reasonable time frame.” . In other words, it’s a good size and not too weird.
The brain was sliced into incredibly thin layers, imaged by EM, and the slices obtained were carefully examined to see how neurons and axons and other cellular structures continued between them. It became clear. “We developed algorithms to track signal propagation across the brain via polysynaptic pathways, analyzing feedforward (from sensory to output) and feedback pathways, multisensory integration, and interactions between hemispheres.” they write.
Serial-section electron microscopy volumes revealing Drosophila brain structures. Image credit: Michael Winding
The result is a model that looks like a slug in a clown wig (no need to add that this is not what it actually looks like). live).
Of course, there are many interesting observations about how the brain organizes, such as nested repetitive loops, multisensory integration, and interhemispheric interactions. But having a complete connectome of a complex organism is fundamentally exciting for anyone in the field. With a good simulation of the brain, there’s a lot you can do. While previous studies have recapitulated individual subsystems or smaller brains, this is the largest and most complete characterization to date and, as a 3D digital resource, will almost certainly be used and cited throughout the field. will be
Some of these are also found in artificial neural networks. Studying how such underpopulated brains produce complex behaviors could “perhaps inspire new machine learning architectures.”
Interestingly, we already have detailed mechanical models of the body and movements of adult flies. The question is clear, but the answer is no. You can’t say you put this brain in that body and simulated the whole thing. thing. But maybe next year.
