基于格兰杰因果性的行走状态下脑肌电同步分析

Corticomuscular Synchronization Analysis Based on Granger Causality during Walking

为了研究健康人在行走过程中大脑皮层与肌肉间的功能性关联,探究正走与倒走过程中该功能联系是否存在差异,分别对10名健康被试进行时长大于10 min的正走和倒走测试;基于格兰杰因果性算法(GC)对测试过程中同步采集到的头皮脑电(EEG)与表面肌电(EMG)信号进行分析,进一步定义不同节律下EEG和不同肌肉EMG的GC显著性面积指标,用以定量描述皮层-肌肉间的功能性耦合关系和信息流向,并分析脑电功率谱与该功能性耦合关系的联系。Wilcoxon非参数检验的结果显示,倒走过程中股直肌与胫骨前肌在EEG→EMG和EMG→EEG方向上alpha和beta节律的GC显著性面积指标较正走过程存在显著下降(P<0.05);线性回归分析的结果显示,正走和倒走中的EEG功率谱峰值与EEG→EMG方向的GC峰值存在线性相关性(P<0.05)。实验说明,健康人步行时EEG和EMG间存在方向性耦合关系,并且脑电alpha和beta节律参与步行中的控制反馈过程,从而证明该研究方法可以刻画大脑皮层与肌肉之间的同步特征与功能联系。

The aim of this study is to investigate functional relationship between brain cortex and muscles during walking and explore the differences of the functional relationships between forward and backward walking. This article collects the EEG and EMG datasets which acquired simultaneously from 10 healthy subjects during forward and backward walking. Granger causality （GC） method, which can reveal the coupling connection and information flow direction among two signals, was applied to analyze the EEG and surface EMG data. Further, the EEG-EMG significant GC area was defined to quantitatively describe the corticomuscular function coupling and information flow direction of different muscles at different frequencies. Then the EEG spectral power was calculated to analyze the relationship with corticomuscular function coupling. The results of Wilcoxon test show that during backward walking, the EEG→EMG and EMG→EEG significant GC area indexes of rectus femoris and tibialis anterior muscle were lower compared with forward walking （α = 0. 05, P 〈 0.05 ） , and a linear relationship exists between EEG spectral power peak and GC peak at EEG→EMG based on linear regression analysis（α= 0. 05, P 〈 0.05 ）. These illustrate that there exists directed coupling between EEG and EMG during walking, and alpha and beta rhythm involve the control and feedback process of walking. It verifies thatthe proposed methods can further describe the synchronization feature and functional connection between cortex and muscles.