Our brain maps our body to facilitate precise motor control; disorders of this body mapping lead to motor deficits. For a century, body mapping has been thought to apply to all types of motor actions. Yet scientists have begun to question how the body map functions when performing different motor actions, such as moving the eyes and hands together.
A recent research paper by Professor Kazumichi Matsumiya of Tohoku University’s Graduate School of Information Sciences revealed that the body relies on multiple maps based on the choice of the motor system.
Details of his research were published in the journal Proceedings of the National Academy of Sciences of the United States of America on January 19, 2022.
Patients with motor dysfunction have abnormalities of the hands and feet that are felt in the brain. Traditional rehabilitation takes into account physical dysfunctions. But the recovery of neurological aspects is not visible and subjective.
To learn more about our body map, Matsumiya set up an experiment where participants were asked to point to different parts of their right hand with the index finger of their left hand while simultaneously tracking with their eyes. This allowed him to measure the mental perception of the right hand for the eyes and movements of the left hand.
Although the left eye and hand were pointing at the same points, the pointing imagery was more distorted, demonstrating the existence of a distinct body map.
Matsumiya expects his discoveries to contribute to the development of new techniques for diagnosing motor dysfunctions. “Today, the Japanese population is aging rapidly, so we are seeing a sharp increase in the number of patients with motor dysfunctions. A better understanding of how patients’ bodies are perceived by their minds will help build a rehabilitation technique more efficient.”
Reference: Matsumiya K. Multiple body schema representations for the same body part. PNAS. 2022;119(4). doi: 10.1073/pnas.2112318119
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