Led by a Chinese scientific team, the world's only "brain map" is published in the world's top magazine

What cells does the brain consist of? What is the law of the spatial distribution of brain cells? These are basic questions in brain science.

If the types, morphologies, distributions, connections, and gene expressions of the tens of billions of cells in the human brain could be depicted in the form of a map, then brain scientists' understanding of the brain would be as clear as you and I looking at a map.

It will take a long time to draw a map of human brain cells, but the map of monkey brains has already been launched. On July 12, the journal Cell published the world's first single-cell resolution and most complete spatial distribution map of macaque cerebral cortex cells to date, which was completed by a Chinese scientific team .

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The cerebral cortex is the outermost layer of the brain and has many valuable cognitive functions , including reasoning, decision-making, and adapting to changing environments. Compared with other animals, primates, represented by humans, have a much larger cortex. Scientists have always believed that it is this evolutionary feature that gives our brains complex computing capabilities.

So how exactly does the cortex function?

The performance of a computer is determined by its individual components and how they are arranged and wired together—“structure determines function.” This is also a key law of biology.

The cerebral cortex is a complex six-layer structure filled with various types of neurons and non-neuronal cells . The type and characteristics, distribution and organization of each cell determine the function of the cerebral cortex. The most fundamental way for scientists to analyze the function is to accurately catalog the cells.

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Neurons are undoubtedly the protagonists. They are electrically activated, transmit electrical signals, and connect to form neural networks to process information. There are two types of neurons that influence the balance of brain activity:

1. Glutamate neurons , also known as excitatory neurons, can improve the brain's computing ability;

2. GABAergic neurons , also known as inhibitory neurons, reduce the activity of neural networks.

Non-neuronal cells are less important than neurons, but they are by no means supporting roles. They help protect the brain from infection, support neural metabolism, and clean up molecular waste. Recent studies have also shown that non-neuronal cells are essential for the formation of neural networks in the early stages of development and are irreplaceable in fighting neurodegenerative diseases such as Alzheimer's disease .

The author team of the new study used spatiotemporal omics technology (Stereo-seq) to extract genetic information (transcriptome) from multiple cells at the same time, recording the activity of about 500 genes for each cell, thereby creating a molecular fingerprint for each cell, and then using AI tools to classify nearly 1.5 million cells from 143 regions into 264 different types and map their locations in the cortex. Among them, excitatory neurons accounted for the largest proportion, about 60% to 70%, and the rest were inhibitory neurons and non-neuronal cells.

The complex and detailed cellular cataloging has brought profound insights.

The research team found that cortical brain cells tend to be distributed in "cliques", and the distribution of a large number of excitatory neurons, inhibitory neurons, and non-neuronal cells shows significant cortical and brain region specificity. Different cortical layers have different types of cells, and brain regions at the same level often gather similar cell types.

In addition, they also discovered six types of excitatory neurons unique to primates, distributed in the fourth layer of the cortex; these cells highly expressed genes related to human diseases , such as language dysfunction and intellectual disability.

This work can help scientists gain a deeper understanding of brain cell interactions, neural information transmission, brain region functions, and other issues, and research and development work on some brain diseases will also benefit from it. We may even get inspiration for AI from brain maps.

Academician Muming Poo, academic director of the Center for Brain and Intelligence Excellence of the Chinese Academy of Sciences, said: "In the future, the team will continue to carry out cross-institutional and cross-field cooperation in the fields of brain disease mechanisms and target research and development, brain cell and brain structure evolution, and cellular and molecular mechanisms of brain function, so as to promote China to continue to produce original and leading results in these fields."

References

Scientists Just Unveiled the Most Complete Map of the Monkey Cortex Yet

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Source: World Science

Editor: Cui Yinghao

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