Neuromuscular Electrical Stimulation with Kilohertz Frequency Alternating Current to Enhance Sensorimotor Cortical Excitability

Enhancement of cortical excitability has been demonstrated to be beneficial for neural recovery of motor dysfunction, such as stroke and spinal cord injury. Neuromuscular electrical stimulation (NMES) has been widely used to evoke limb movements, resulting in the increasing cortical excitability. Due to the advantages of low skin impedance and less discomfort, an alternative NMES of kilohertz frequency alternating current (KFAC) has been proposed, and the effects of current parameters on evoked torque has been studied. However, few studies concerned cortical excitability effects during KFAC-evoked limb movement. In this paper, we utilized the event-related spectral estimation (ERSP) to calculate the beta ERD values to investigate the effects of KFAC-evoked elbow flexion movement on cortical excitability and compared them with that of passive movement. Firstly, averaged ERSP values were extracted in beta band during elbow flexion movements by sliding a 2Hz wide window for all trails of each subject. And then the minimal value was chosen as the representative value of beta ERD. Finally, the absolute ERD values and the descending slopes of all subjects were both calculated for statistical analysis by one-way repeated measures ANOVA. The results showed KFAC can increase cortical excitability, especially with long pulse duration. Moreover, beta cortical activities during KFAC500-evoked movement are significantly activated than those during passive movement. Therefore, our study may provide a new NMES rehabilitation method to enhance cortical excitability for motor dysfunction patients.