Multiscale information interaction at local frequency band in functional corticomuscular coupling

Post-Stroke Corticomuscular Coupling Assessment Based on Bilateral Cerebral Hemisphere Difference

Corticomuscular coupling (CMC) can quantify the information interaction between the brain and muscles during motor control. However, current research regarding changes in CMC after stroke is inconsistent. To address this, this paper propose a novel use of $\textit {CMC}_{\textit {dif}}$ as an indicator to assess motor function after stroke. This indicator include $\textit {WC}_{\textit {dif}}$ , derived from wavelet coherence analysis and $\textit {TSE}_{\textit {dif}}$ , derived from transfer spectral entropy analysis. Twelve stroke patients and twelve healthy controls were included in this study, with an experimental paradigm of upper limb isokinetic push-pull movements. The results revealed that $\textit {WC}_{\textit {dif}}$ were significantly higher in the stroke patient group compared to the healthy group. Moreover, the $\textit {TSE}_{\textit {dif}}$ of stroke group is higher than healthy group on the efferent pathway, but no difference on the afferent pathway. Utilizing the validated $\textit {CMC}_{\textit {dif}}$ indices, we developed a motor function assessment model that showed strong relation with clinical assessment outcomes ( ${R}^{{2}}={0}.{873}$ , ${p}={0}.{003}$ ). These findings provide a new insight to understand the mechanisms underlying CMC changes after stroke. The combined use of linear and nonlinear indicators enhances the potential of CMC for clinical motor function assessment in stroke patients.

Analysis of Cortico-Muscular Coupling and Functional Brain Network under Different Standing Balance Paradigms

Maintaining standing balance is essential for people to engage in productive activities in daily life. However, the process of interaction between the cortex and the muscles during balance regulation is understudied. Four balance paradigms of different difficulty were designed by closing eyes and laying sponge pad under feet. Ten healthy subjects were recruited to stand for ten 15 s trials in each paradigm. This study used simultaneously acquired electroencephalography (EEG) and electromyography (EMG) to investigate changes in the human cortico-muscular coupling relationship and functional brain network characteristics during balance control. The coherence and causality of EEG and EMG signals were calculated by magnitude-squared coherence (MSC) and transfer entropy (TE). It was found that changes in balance strategies may lead to a shift in cortico-muscular coherence (CMC) from the beta band to the gamma band when the difficulty of balance increased. As subjects performed the four standing balance paradigms, the causality of the beta band and the gamma band was stronger in the descending neural pathway than that in the ascending neural pathway. A multi-rhythmic functional brain network with 19 EEG channels was constructed and analyzed based on graph theory, showing that its topology also changed with changes in balance difficulty. These results show an active adjustment of the sensorimotor system under different balance paradigms and provide new insights into the endogenous physiological mechanisms underlying the control of standing balance.