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Zhejiang University scientists developed a method for mapping brain functional connections in vivo

[发布人]:cjg[发布日期]:2019-04-25[访问次数]:2247

The brain is made up of “cities” and “buildings” with different functions. Numerous neural connections are like “information roads” that connect them into a network. Based on the brain network, information is transmitted from sensory input, processed in the brain, and ultimately produces memories, emotions, and behaviors. Therefore, understanding the brain requires mastering the “brain map”, which is like having a map when people travel. However, at present, when brain scientists explore the mysteries of the brain, but there is no complete "brain traffic map" for reference.

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On April 24th, local time, the team of Anna Wang Roe, Institute of Systematic Neurology and Cognition, Zhejiang University, published a brain network study online in Science Advances. The latest breakthrough in the method. Their new technology, INS-fMRI, combines infrared light stimulation with magnetic resonance imaging for the first time. This new method allows sub-millimeter brain connections in the living brain, enabling us to be faster and more systematic. Look at the "brain traffic map" to understand the transmission of information. “It’s like, we can not only know that a package departs from a laboratory building in Zhejiang University in Hangzhou to Beijing, but also knows its destination details such as district, street, building and even floor number” Xu Guohua, the first author of the article Introduced in the interview.

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Other participants in the study included the co-first author, PhD studeng Qian Meizhen, correspondent author Dr. Zhang Xiaotong, Dr. Chen Gang and Dr. Anna Wang Roe. They developed INS-fMRI technology to study brain networks in vivo, and their characteristics can be summarized as faster, stronger, and higher.

faster

The anatomical methods used to map brain connections usually involve injecting dyes at several initial locations in the brain, taking weeks to transport the dye and "painting" the nerve connections, then sacrificing the animal to make the brain slices, and finally very time-consuming image reconstruction and analysis. Even so, only a few injection sites can be studied in an animal.

The new technology invented by this research group combines laser stimulation and magnetic resonance imaging to quickly display in three dimensions. Preliminary results can be obtained in 1-2 hours of scanning, which is very convenient for studying brain regions at the whole brain level. The degree of response can be quickly studied in a single-day experiment. Xu Guohua said: "Instead of slowly coloring the road, it is better to send a bunch of express delivery from Hangzhou. In a very short time, we can know which cities they have arrived in."

“In addition, the benefits of INS-fMRI technology are not only fast, but also facilitate the in vivo experiments, greatly reducing the number of animals used, and conducting multiple follow-up studies on the same animal, such as studying brain development,” Wang Jing The professor said.

stronger

Stronger performance means quantifiable and more accurate.

The infrared pulse is illuminated by a 200 micron diameter fiber to the target brain region, causing a neural response in the brain region and associated brain regions. Once the signal is activated, it will cause blood oxygen changes. This blood oxygen signal can be captured by magnetic resonance imaging. "The strength of the connection can be quantified as the magnitude and correlation of the response via the blood oxygenation reaction," Xu Guohua said.

In the early years, Professor Wang Jing was inspired by the use of laser instead of current-activated neurons in cochlear implant research. She began this research and became the first scientist to introduce infrared light stimulation into brain research. The significance of this shift is about precision, the infrared light pulse delivers energy to a very small space, achieving precise stimulation and causing spatial specificity of the connected sites.

higher

Higher performance is high resolution. When using ultra-high field (7 Tesla) magnetic resonance imaging, these response positions can be presented at sub-millimeter resolution. This provides the basis for studying the activities of the various cortical functional columns ("buildings") and the various layers of the cortex ("floors"). "We combined the infrared light stimulation method with functional magnetic resonance and proposed this experimental method for the first time in the world." Wang Jing said.

The so-called functional column is an information processing unit inside the brain, and the size is only two or three hundred micrometers. The primate brains are arranged neatly by these functional columns; each functional column happens to correspond to a specific cognitive function and is connected to each other as a network. Therefore, for primates including humans, it is especially important to map brain connections between macro and micro scales.

However, researchers currently only know that functional columns are functional units, but it is not clear how they are specifically connected. Xu Guohua explained: "It's like many tall buildings with different functions, some schools, some hospitals, etc., but we don't understand how these buildings are connecting."

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“This method can be used to systematically stimulate the cortical function column one by one to fully depict the primate mesoscopic connectome.” Wang Jing introduced that this new technology will be a whole brain network with high-resolution functional columns. The map lays the foundation and opens the door for large-scale research. By clarifying the connections between the various functional columns, it will greatly help us understand how the primate (including human) brain works and brain diseases, and will promote the development of neuroscience, psychology, medicine and artificial intelligence.

In the Science Advances article, the research team reported two application examples, corresponding to the study of long-range connections at the whole brain scale, and high-resolution short-range connections within a local range. Experiments have shown that the application of this new method will probably help us to understand the connection and working principle of the brain, and then better understand the disease and precisely regulate the related brain structure and function.

Paper link:  https://advances.sciencemag.org/content/5/4/eaau7046

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