The application of fNIRS-sEMG in the study of muscle-brain coupling

With the rapid development of functional near-infrared spectroscopy and surface electromyography, combining the two offers a new way to accurately evaluate muscle-brain coupling, with unique advantages for research on real motor control and neural rehabilitation. This paper analyzes the principle of combined technology, commonly used coupling indicators, and their application in nervous system diseases, motor control in healthy people, and chronic pain diseases. After summarizing, it is found that there is a stable and repeatable functional coupling relationship between specific cortical regions and specific muscle groups. A significant reduction in cortical-muscle coupling accompanied compensatory cortical hyperactivation. The coupling laws of different populations are different. Under the state of exercise in healthy people, the specific functional brain areas, such as the primary motor cortex and primary sensory cortex, can form a stable and repeatable specific functional coupling relationship with the corresponding muscle groups of the body, and the coupling strength is highly matched with movement accuracy, muscle force output, and motor coordination. Patients with nervous system diseases have typical characteristics of abnormal neural remodeling, which are generally manifested as compensatory overactivation of specific cortex and disturbed resource allocation in brain regions, accompanied by multiple pathological features such as significant attenuation of cortical-muscle coupling efficiency, disturbance of coupling rhythm, and decreased synchrony. Patients with chronic pain have abnormal regulation of brain areas and an imbalance of muscle activation. Due to the difference in sampling rate between fNIRS and sEMG, there are some challenges in signal processing, and there is no unified and standardized signal processing and data analysis system, which limits the versatility and standardization of this technique to a certain extent. However, fNIRS-sEMG is still one of the preferred methods to evaluate the muscle-brain coupling at present.