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New brain maps reveal how we control body movements


The human brain has a prominent anterior central gyrus, which is located in the motor cortex. Credit: Science Photo Library/Getty Images

For nearly a century, it was thought that the motor cortex, a thin strip of tissue across the top of the brain, controlled body movement. But new research published in Nature suggests that body movement may be controlled by two different networks in the brain, not just this one.

In the 2030s, neuroscientists Wilder Penfield and Edwin Boldrey performed electrical stimulation on the brains of people undergoing brain surgery, and the results showed that different areas of the primary motor cortex controlled different parts of the body. They also found that these control areas were arranged in the same order as the body parts they controlled, with the toes at one end and the face at the other.

Evan Gordon and colleagues at the University of Washington School of Medicine in Missouri hope to use modern technology to study Penfield and Boldrey’s findings in more detail. They performed high-resolution MRI brain scans of seven people and had them lie in the scanner looking at a cross symbol for 12 to 15 hours.

Gordon said that when participants were largely stationary and not engaged in complex tasks such as reading, their brain activity data was simpler, and analyzing the brain could allow researchers to better observe which areas of the brain were working.

The brain map drawn by Penfield-Boldrey suggests that one area of the primary motor cortex is associated with movement of the lower body, one with hand-related movements including the shoulders, and the other with facial movements.

But Gordon and his team found that beyond these three specific regions, there are 3 more regions of the cerebral cortex scattered across the brain map that appear to work together to coordinate movements in body centers, such as the shoulders and abdomen. Further imaging experiments showed that these areas became particularly active when the abdomen was moved.

The researchers named these intermediate regions the Somatic Sensory-Cognitive Activity Network (SCAN), which constitutes a second, distinct motor network in our brains.

The researchers then looked for signs of SCAN from brain activity data obtained from several major databases, such as the Human Connectome Project and the UK Biobank, and found that it appeared to be present in all the samples they analyzed.

Gordon said the SCAN network appears to work in tandem with the first network of the primary motor cortex, which controls movements related to the hands, feet and mouth. While movement in other parts of the body, such as the hips or back, may be controlled by other areas of the motor cortex, which have not been mapped out in detail.

In another part of the experiment, the researchers scanned the brains of three children — one newborn, one 11 months old and one 9 years old — to see if they had SCAN.

While they didn’t see the network in newborns, it was found in both 11-month-old and 9-year-olds, suggesting that it develops as the baby grows. Gordon said: “An 11-month-old baby can consciously move his arms and legs. Newborns, on the other hand, have little control over their body movements. ”

The team wanted to know if SCAN was linked to diseases such as Parkinson’s disease. Parkinson’s disease affects movement, causing symptoms such as tremors. While further research is needed, SCAN could be a therapeutic target for Parkinson’s disease and other exercise-related diseases, Gordon said.

“This is a new contribution to a long-standing neuroscience problem in neuroscience about the mechanisms used by neurons in the motor cortex to control movement.” Patrick Haggard of University College London said that to test these results, it would be useful to record SCAN neurons in experiments where humans or other animals can move freely, not just scanners. (Source: Li Huiyu, China Science News)

Related paper information:http://doi.org/10.1038/s41586-023-05964-2



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