Mapping fly brains - Only 2 crore steps needed!

Understanding how a fruitfly brain works, to get a deeper handle on how nature evolves.

 Mapping fly brains - Only 2 crore steps needed!

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• The story: The brain of a fruit fly is the size of a poppy seed and about as easy to overlook. Most people don’t even think of the fly as having a brain! But flies lead quite rich lives, as scientists discovered. They are capable of sophisticated behaviors, and their specksize brains are tremendously complex, containing about 1,00,000 neurons and tens of millions of connections, or synapses, between them.
• Research into flies: Since 2014, a team of scientists at Janelia, in collaboration with researchers at Google, have been mapping these neurons and synapses in an effort to create a comprehensive wiring diagram, also known as a connectome, of the fruit fly brain. By analysing the connectome of just a small part of the fly brain the team identified dozens of new neuron types and pinpointed neural circuits that appear to help flies make their way through the world.

1. The work is time-consuming and expensive, even with the help of state-of-the-art machine-learning algorithms.
2. But the data released so far is stunning in its detail, composing an atlas of gnarled neurons in many crucial areas of the fly brain.

• What to do with it: By analysing the connectome of just a small part of the fly brain — the central complex, which plays an important role in navigation, scientists identified dozens of new neuron types and pinpointed neural circuits that appear to help flies make their way through the world. The work could help provide insight into how all kinds of animal brains process a flood of sensory information and translate it into appropriate action. It is also a proof of principle for the young field of "modern connectomics", which was built on the promise that constructing detailed diagrams of the brain’s wiring would pay scientific dividends.
• Only full connectome so far: The only complete connectome in the animal kingdom belongs to the humble roundworm, C. elegans. Biologist Sydney Brenner, who would later go on to win a Nobel Prize, started the project in the 1960s. His small team spent years on it, using colored pens to trace all 302 neurons by hand.
• Fruit fly brain: The latest project started in 2014, with the brain of a single, 5-day-old female fruit fly. Researchers cut the fly brain into slabs and then used a technique known as focused-ion beam scanning electron microscopy to image them, layer by painstaking layer. The microscope functioned like a tiny, precise nail file, filing away an exceedingly thin layer of the brain, snapping a picture of the exposed tissue and then repeating the process until nothing remained.

1. The work involves simultaneous imaging and cutting off of little slices of the fly brain, so they don’t exist after it's done
2. The team used computer vision software to stitch the millions of resulting images back together into a single, 3D volume and sent it off to Google.
3. Researchers then used advanced machine-learning algorithms to identify each individual neuron and trace its twisting branches.
4. Finally additional computational tools were used to pinpoint the synapses, and human researchers proofread the computers’ work, correcting errors and refining the wiring diagrams.
5. Then came the connectome for what was called the “hemibrain,” a large portion of the central fly brain, which includes regions and structures that are crucial for sleep, learning and navigation. The connectome, which is accessible free online, includes about 25,000 neurons and 20 million synapses, far more than the C. elegans connectome.
6. Once the hemibrain connectome was ready, the data on the central complex was tackled.
7. The brain region, which contains nearly 3,000 neurons and is present in all insects, helps flies build an internal model of their spatial relationship to the world and then select and execute behaviors appropriate for their circumstances, such as searching for food.

• How brain works: The researchers hypothesise that fly brains may be wired to prioritize information about the global environment when they are navigating, but also that these circuits are flexible, so that when such information is inadequate, they can pay more attention to local features of the landscape.

1. Flies are not mice or chimps or humans, but their brains perform some of the same basic tasks. Understanding the basic neural circuitry in an insect could provide important clues to how other animal brains approach similar problems.
2. Gaining a deep understanding of the fly’s brain also gives insights that are very relevant to the understanding of mammalian, and even human, brains and behavior.
3. Creating connectomes of larger, more complex brains will be enormously challenging. The mouse brain contains roughly 70 million neurons, the human brain a whopping 86 billion. But the central complex paper is decidedly not a one-off; detailed studies of regional mouse and human connectomes are in the pipeline.

• EXAM QUESTIONS: (1) Explain the working of a fly brain, and why understanding its connectome could open new vistas for science. (2) Explain the basic rules of how the process of evolution works in humans.

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#Flybrain #neurons #connectome #neuralconnections

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