Relating Facial Myoelectric Activity to Speech Formants

Speech articulation is conditioned by the movements produced by well determined groups of muscles in the larynx, pharynx, mouth and face. The resulting speech shows acoustic features which are directly related with muscle neuromotor actions. Formants are some of the observable correlates most related to certain muscle actions, such as the ones activating jaw and tongue. As the recording of speech is simple and ubiquitous, the use of speech as a vehicular tool for neuromotor action monitoring would open a wide set of applications in the study of functional grading of neurodegenerative diseases. A relevant question is how far speech correlates and neuromotor action are related. This question is answered by the present study using electromyographic recordings on the masseter and the acoustic kinematics related with the first formant. Correlation measurements help in establishing a clear relation between the time derivative of the first formant and the masseter myoelectric activity. Monitoring disease progress by acoustic kinematics in one case of Amyotrophic Lateral Sclerosis ALS is described.