The first complete map of every neuron in the brain has been revealed

Imagine staring at the complex and beautiful map of an entire city, but the city is actually a brain. Sounds great, doesn't it? Well, scientists have now made this a reality.

Experts have created the first-ever wiring diagram, or 'neural network', of every neuron in an adult's brain as well as the 50 million connections between them, marking a milestone in the field of neuroscience.

Complete brain wiring diagram

This project was made possible thanks to the FlyWire Consortium, a large international collaboration involving scientists from around the world MRC Laboratory of Molecular Biology At Cambridge, Princeton University, the University of Vermont, and Princeton University University of Cambridge.

Research that is published in a pair of papers in a journal natureProvides the first complete connectivity diagram of all 139,255 neurons in the brain of an adult fly – an animal capable of walking and seeing.

Previous studies have mapped smaller brain systems, such as the fruit fly larva, which contains 3,016 neurons, or the nematode worm, which contains 302 neurons.

However, the current study breaks new ground by providing a full-scale neural map of a more complex organism.

Human brains versus fly brains

Mapping every neuron in the adult fruit fly brain is a key step in understanding how brains, including our own, work.

The fruit fly has about 140,000 neurons, a small number compared to the 86 billion neurons in the human brain, which makes it much easier to study.

Scientists can rapidly breed and modify fruit flies, allowing them to manipulate genetics and see how changes affect neural circuits and behavior.

This simplicity helps researchers discover the basic principles of brain function without getting bogged down in too much complexity.

Brain maps provide insights into the human brain

Interestingly, many biological processes in fruit flies are very similar to those in humans. Genes and pathways that control brain development, neuron connections, and learning are often conserved across species.

By mapping the fruit fly brain, scientists can learn how these processes work in a simpler system and then apply those insights to more complex brains.

In addition, understanding how neurons in flies communicate reveals general patterns of organization and behavior of neural circuits, which can help us understand human behaviors and cognitive functions as well.

Finally, the tools and techniques developed to map the Drosophila brain have paved the way for breakthroughs in neuroscience research. Innovations in imaging, genetic manipulation, and data analysis from Drosophila studies can be adapted to study more complex brains, including our own.

Insights from fruit flies could also help model neurological diseases and developmental disorders, leading to potential treatments for humans.

Ongoing research in neuroscience

The findings provide valuable insights into brain structure and function, providing a vital comparison to ongoing research in neuroscience.

“If we want to understand how the brain works, we need a mechanistic understanding of how all the neurons fit together and allow you to think. For most brains, we have no idea how these networks work.

A detailed map of the fly brain could answer many of these questions, and reveal the complexities of neural circuits.

Similarities in brain wiring

One of the most notable findings of the study is the strong similarity in the connections found between the current map and previous, smaller-scale efforts.

This has led to the conclusion that individual brains share inherent similarities in their wiring, contrary to the belief that each brain is a unique structure.

A brain mapping journey

The path to this feat involved slicing an entire fly brain, which is less than a millimeter wide, into 7,000 thin slices.

These slices were then carefully examined using a high-resolution electron microscope to extract the shapes of approximately 140,000 neurons and the 50 million connections between them.

The power of artificial intelligence

The task of analyzing this massive amount of data is made possible using machine learning, demonstrating the potential of AI technology to revolutionize neuroscience.

Ensuring data accuracy requires an estimated 33 years of proofreading work. Despite the challenges, the results of this rigorous endeavor have paved the way for future discoveries in neuroscience.

Beyond simply establishing neural connections, the researchers also accounted for many details of the wiring diagram, such as the classification of more than 8,000 cell types across the brain.

“This dataset is a bit like Google Maps, but for brains: the initial connectivity diagram between neurons is like knowing which structures on satellite images of the Earth correspond to which streets and buildings,” explained Dr. Philipp Schlegel, first author of one of the studies. studies.

Simulating brain functions

The researchers' work extends beyond just mapping. They also used AI image scanning technology to predict whether each synapse was inhibitory or excitatory, an important aspect of digitally simulating the brain.

“Using our data, which was shared online as we worked, other scientists have already begun trying to mimic how the fly brain responds to the outside world,” Dr Jeffress said.

“This is an important start, but we will need to collect many different types of data to produce a reliable simulation of how the brain works.”

Future research directions

This research has undoubtedly revolutionized our understanding of the brain, but the journey is far from over. As we move forward, future studies will explore differences in neural architecture between the brains of male and female flies.

“The comprehensiveness of our wiring diagram has great benefits for brain research and enables many types of studies that were not previously possible using wiring diagrams of parts of the fly brain,” the researchers noted.

The study is published in the journal nature.

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