EEG-based communication: analysis of concurrent EMG activity

Objective: Recent studies indicate that people can learn to control the amplitude of mu or beta rhythms in the EEG recorded from the scalp over sensorimotor cortex and can use that control to move a cursor to targets on the computer screen. While subjects do not move during performance, it is possible that inapparent or unconscious muscle contractions contribute to the changes in the mu and beta rhythm activity responsible for cursor movement. We evaluated this possibility.

Methods: EMG was recorded from 10 distal limb muscle groups while five trained subjects used mu or beta rhythms to move a cursor to targets at the bottom or top edge of a computer screen.

Results: EMG activity was very low during performance, averaging 4.0±4.4% (SD) of maximum voluntary contraction. Most important, the correlation, measured as r², between target position and EMG activity averaged only 0.01±0.02, much lower than the correlation between target position and the EEG activity that controlled cursor movement, which averaged 0.39±0.18.

Conclusions: These results strongly support the conclusion that EEG-based cursor control does no depend on concurrent muscle activity. EEG-based communication and control might provide a new augmentative communication option for those with severe motor disabilities.