Tension in the two frontales: electrode placement and artifact in the recording of forehead EMG.
D000200:Action Potentials; D001676:Biofeedback, Psychology; D004569:Electroencephalography / Q000379:methods; D004576:Electromyography / Q000379:methods*; D005546:Forehead; D006801:Humans; D009129:Muscle Tonus