Correlation between EEG–EMG coherence during isometric contraction and its imaginary execution

To assess the similarity between cortical activities observed during actual and imaginary motor tasks, we evaluated electroencephalography–electromyography (EEG–EMG) coherence during motor task execution (ME) and the same task-related EEG power increase (TRPI) during kinesthetic motor imagery (MI). EEGs recorded at the vertex and EMGs recorded at the right tibialis anterior muscle (TA) were analyzed in 13 healthy subjects. Subjects were requested to perform: (1) isometric TA contraction, (2) imagery of the same movement without overt motor behavior, and (3) rest without MI. The results show significant EEG–EMG coherence during ME, as well as TRPI during both ME and MI tasks within a similar 14–30 Hz band. The magnitude of EEG–EMG coherence and TRPI varied among the subjects. Intersubject analysis revealed a significant correlation between EEG–EMG coherence and TRPI. These results support the hypothesis that ME and MI tasks involve overlapping neural networks in the perirolandic cortical areas.