Association of Orofacial Muscle Activity and Movement During Changes in Speech Rate and Intensity Understanding how orofacial muscle activity and movement covary across changes in speech rate and intensity has implications for the neural control of speech production and the use of clinical procedures that manipulate speech prosody. The present study involved a correlation analysis relating average lower-lip and jaw-muscle activity to lip and ... Research Article
Research Article  |   December 01, 2003
Association of Orofacial Muscle Activity and Movement During Changes in Speech Rate and Intensity
 
Author Affiliations & Notes
  • Michael D. McClean
    Western Michigan University, Kalamazoo, and Army Audiology and Speech Center, Walter Reed Army Medical Center, Washington, DC
  • Stephen M. Tasko
    Western Michigan University, Kalamazoo
  • Contact author: Michael McClean, PhD, Department of Speech Pathology and Audiology, Western Michigan University, Kalamazoo, MI 49008. E-mail: michael.mcclean@wmich.edu
Article Information
Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   December 01, 2003
Association of Orofacial Muscle Activity and Movement During Changes in Speech Rate and Intensity
Journal of Speech, Language, and Hearing Research, December 2003, Vol. 46, 1387-1400. doi:10.1044/1092-4388(2003/108)
History: Received January 12, 2003 , Accepted March 12, 2003
 
Journal of Speech, Language, and Hearing Research, December 2003, Vol. 46, 1387-1400. doi:10.1044/1092-4388(2003/108)
History: Received January 12, 2003; Accepted March 12, 2003
Web of Science® Times Cited: 30

Understanding how orofacial muscle activity and movement covary across changes in speech rate and intensity has implications for the neural control of speech production and the use of clinical procedures that manipulate speech prosody. The present study involved a correlation analysis relating average lower-lip and jaw-muscle activity to lip and jaw movement distance, speed, and duration. Recordings were obtained on orofacial movement, muscle activity, and the acoustic signal in 3 normal speakers as they repeated a simple test utterance with targeted speech rates varying from 60% to 160% of their habitual rate and at targeted vocal intensities of –6 dB and +6 dB relative to their habitual intensity. Surface electromyographic (EMG) recordings were obtained with electrodes positioned to sample primarily the mentalis, depressor labii inferior, anterior belly of the digastric, and masseter muscles. Two-dimensional displacements of the lower lip and jaw in the midsagittal plane were recorded with an electromagnetic system. All participants produced linear changes in percent utterance duration relative to the auditory targets for speech rate variation. Intensity variations ranged from –10 dB to +8 dB. Average EMG levels for all 4 muscles were well correlated with specific parameters of movement. Across the intensity conditions, EMG level was positively correlated with movement speed and distance in all participants. Across the rate conditions, EMG level was negatively correlated with movement duration in all participants, while greater interparticipant variability was noted for correlations relating EMG to speed and distance. For intensity control, it is suggested that converging neural input to orofacial motoneurons varies monotonically with movement distance and speed. In contrast, rate control appears to be more strongly related to the temporal characteristics of neural input than activation level.

Acknowledgments
This research was supported in part by National Institutes of Health Grant DC 03659 and was approved by the Walter Reed Army Medical Center Human Use Committee, under Department of Clinical Investigation Work Units 2550 and 2585. All participants enrolled in the study voluntarily agreed to participate and gave written and informed consent. The opinions or assertions herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.
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