Sensorimotor Cortical Activities Induced by NMES During INB

Ischemic nerve block (INB) can successfully separate muscle spindle afferents from sensory afferents evoked by neuromuscular electrical stimulation (NMES) above motor threshold. The purpose of this study is to explore how the sensorimotor cortex perceives the incoming muscle spindle afferents evoked by NMES above motor threshold during INB. An experimental protocol was composed by four tasks conceived according to a 2 × 2 factorial design. In particular, the first factor was the INB state (Before INB and during INB) and the second factor was the NMES intensity (Sup− and sub−motor threshold). During the tasks, 64-channel EEG signals from 11 healthy subjects were record and analyzed to detect beta event-related desynchronization (Beta ERD) for quantizing the activation level of sensorimotor cortex. The psychophysical test was used to assess changes in sensation and movement of the right hand when the right wrist was blocked by the blood pressure cuff. At the same time, active and passive index finger flexion and extension tasks were set before and during INB. The statistical results showed that during INB, beta ERD on the contralateral sensorimotor cortex induced by NMES with the sup-motor threshold was significantly decreased, and the difference of Beta ERD values on the contralateral sensorimotor cortex induced by NMES with sup− and sub motor threshold was significant. In addition, contralateral dominance of beta ERD on the sensorimotor cortex induced by NMES was transferred to ipsilateral during INB. INB significantly reduced sensorimotor cortical activity induced by NMES with the sup-motor threshold and decreased its perception on the stimulus intensity, which may result from the rapid functional reorganization of the sensorimotor cortex induced by INB.