Abstract
Neuromuscular electrical stimulation (NMES) is frequently used in rehabilitation therapy to improve motor recovery. To optimize the stimulatory effect of NMES, the parameters of NMES, including stimulation mode, location, current intensity, and duration, among others have been investigated; however, these studies mainly focused on the effects of changing parameters in the current plateau stage of the NMES cycle, while the impacts on other stages, such as the current rising stage, have yet to be investigated. In this article, we studied the electroencephalograph (EEG) effects during NMES, with different rates of current change in the rising stage, and stable current intensity in the plateau stage. EEG signals (64-channel) were collected from 28 healthy subjects, who were administered with high, medium, or low current change rate (CCR) NMES through a right-hand wrist extensor. Time-frequency analysis and brain source analysis, using the LORETA method, were used to investigate neural activity in sensorimotor cortical areas. The strengths of cortical activity induced by different CCR conditions were compared. NMES with a high CCR activated the sensorimotor cortex, despite the NMES current intensity in the plateau stage lower than the motor threshold. Reduction of the Alpha 2 band (10–13 Hz) event related spectral power (ERSP) during NMES stimulation was significantly enhanced by increasing CCR (p < 0.05). LORETA-based source analysis demonstrated that, in addition to typical sensory areas, such as primary somatosensory cortex (S1), sensorimotor areas including primary motor cortex (M1), premotor cortex (PMC), and somatosensory association cortex (SAC) were all activated by within threshold NMES. Furthermore, compared with the low CCR condition, cortical activity was significantly enhanced in the S1, M1, and PMC areas under high CCR conditions. This study shows CCR in the NMES rising stage can affect EEG responses in the sensorimotor cortex and suggests that CCR is an important parameter applicable to the optimization of NMES treatment.
Highlights
Neuromuscular electrical stimulation (NMES) has been widely used in the clinical treatment of motor dysfunction for many years
Even with a stimulation current intensity lower than the motor threshold, the alpha band EEG oscillation was depressed during NMES (Figures 2A–C)
These results indicate that the event-related desynchronization (ERD) alpha band can be induced by NMES within the motor threshold
Summary
Neuromuscular electrical stimulation (NMES) has been widely used in the clinical treatment of motor dysfunction for many years. Based on the review of Chipchase et al (2011) NMES studies includes both functional electrical stimulation (FES) and therapeutic electrical stimulation (TES). Induction of muscle contractions by NMES to supplement or substitute for lost motor functions is referred to as FES (Doucet et al, 2012). For central nervous system diseases, task-related activation method on brain functional areas is as important as motor assistance for rehabilitation. Some of the studies focus on brain activation induced by NMES which played an important role of rehabilitation in the central nervous system injury. Wegrzyk et al (2017) contrasted specific brain activation patterns associated with wide-pulse high-frequency (100 Hz–1 ms) and conventional (25 Hz–0.05 ms) NMES. Increased excitability in surviving neurons might leads to enhanced motor recovery after stroke (Murphy and Corbett, 2009)
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