Abstract
Recently, functional corticomuscular coupling (FCMC) between the cortex and the contralateral muscle has been used to evaluate motor function after stroke. As we know, the motor-control system is a closed-loop system that is regulated by complex self-regulating and interactive mechanisms which operate in multiple spatial and temporal scales. Multiscale analysis can represent the inherent complexity. However, previous studies in FCMC for stroke patients mainly focused on the coupling strength in single-time scale, without considering the changes of the inherently directional and multiscale properties in sensorimotor systems. In this paper, a multiscale-causal model, named multiscale transfer entropy, was used to quantify the functional connection between electroencephalogram over the scalp and electromyogram from the flexor digitorum superficialis (FDS) recorded simultaneously during steady-state grip task in eight stroke patients and eight healthy controls. Our results showed that healthy controls exhibited higher coupling when the scale reached up to about 12, and the FCMC in descending direction was stronger at certain scales (1, 7, 12, and 14) than that in ascending direction. Further analysis showed these multi-time scale characteristics mainly focused on the beta1 band at scale 11 and beta2 band at scale 9, 11, 13, and 15. Compared to controls, the multiscale properties of the FCMC for stroke were changed, the strengths in both directions were reduced, and the gaps between the descending and ascending directions were disappeared over all scales. Further analysis in specific bands showed that the reduced FCMC mainly focused on the alpha2 at higher scale, beta1 and beta2 across almost the entire scales. This study about multi-scale confirms that the FCMC between the brain and muscles is capable of complex and directional characteristics, and these characteristics in functional connection for stroke are destroyed by the structural lesion in the brain that might disrupt coordination, feedback, and information transmission in efferent control and afferent feedback. The study demonstrates for the first time the multiscale and directional characteristics of the FCMC for stroke patients, and provides a preliminary observation for application in clinical assessment following stroke.
Highlights
Motor dysfunction is a major consequence of stroke [1], and the loss of motor function is generally considered as a result of the impairments in neural network that controls movement
There was no steady state during the scale interval from 1 to 20, and even a significant decline in ascending direction for stroke patient S8
Further comparison between the descending and ascending directions showed that the multiscale transfer entropy (MSTE) values in descending direction for most healthy controls were higher at the scale about 5~15 than that in ascending direction
Summary
Motor dysfunction is a major consequence of stroke [1], and the loss of motor function is generally considered as a result of the impairments in neural network that controls movement. An effective and precise assessment on the motor functions of stroke patients plays an important role in motor recovery. The functional corticomuscular coupling (FCMC) between the motor cortex and the effector muscles is considered essential for effective movement control [2]. Oscillations in the gamma-band (35–60 Hz) are related to stronger muscle force production [12, 13] and dynamic force output [6, 14]. These researches reveal that the FCMC in different frequency bands plays different roles in sensory and motor systems in healthy subjects
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
