Neuromuscular specialization of the mandibular motor system: Speech versus non-speech movements

Abstract A number of EMG studies have provided significant contributions to our understanding of the mandibular muscle system. Nevertheless, little is known about the organization of the action patterns of the jaw muscles during movements underlying speech production, in relation to those of other functional activities. In the present study, the activity patterns of the mandibular elevator muscle system were investigated for speech and non-speech gestures for the purpose of determining the possibility of neuromuscular specialization for speech in relation to other mandibular functions. The activity of eight muscles were recorded along with the displacement of the incisal point of the jaw in three-dimensional space. These signals were recorded from three adult American-English subjects during the production of speech at different rates, and for non-speech movements. Results indicated that jaw space for speech was the most restricted of any mandibular function and jaw movements for speech were generally produced by the most simple muscle action patterns. Chewing and functional jaw movements are presumably neurophysiologically distinct. In addition, individual differences exist in the selection of a given muscle or muscle system for a specific function and/or utterance and in the coordination of muscle activity patterns for different gestures.