Procedures for verification of electrode placement in EMG studies of orofacial and mandibular muscles.

Many muscles used in speech are small and intimately interconnected. There is a need for anatomical and physiological data which would allow identification of the particular muscle fibers being recorded in electromyographic (EMG) investigations. EMG recordings were taken from eighteen orofacial and mandibular muscles while gestures believed to be specific to each muscle were performed. The anatomic criteria for the placement of the electrodes, the quality of the EMG spikes and interference patterns obtained, and the degree of differentiation of the temporal sequence of activity from that in neighboring muscles were used to decide on the degree of certainty that a particular muscle was being recorded. The appropriateness of each gesture as a stimulus to any muscle was determined on the basis of the level of activation occurring with the gesture relative to other muscles and its degree of variability between subjects.