Feedforward and Feedback Control in Apraxia of Speech: Effects of Noise Masking on Vowel Production Purpose This study was designed to test two hypotheses about apraxia of speech (AOS) derived from the Directions Into Velocities of Articulators (DIVA) model (Guenther et al., 2006): the feedforward system deficit hypothesis and the feedback system deficit hypothesis. Method The authors used noise masking to minimize auditory ... Research Article
Research Article  |   April 01, 2015
Feedforward and Feedback Control in Apraxia of Speech: Effects of Noise Masking on Vowel Production
 
Author Affiliations & Notes
  • Edwin Maas
    University of Arizona, Tucson
  • Marja-Liisa Mailend
    University of Arizona, Tucson
  • Frank H. Guenther
    Boston University, MA
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication.×
  • Correspondence to Edwin Maas: emaas@email.arizona.edu
  • Editor: Jody Kreiman
    Editor: Jody Kreiman×
  • Associate Editor: Julie Liss
    Associate Editor: Julie Liss×
Article Information
Speech, Voice & Prosodic Disorders / Apraxia of Speech & Childhood Apraxia of Speech / Hearing & Speech Perception / Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   April 01, 2015
Feedforward and Feedback Control in Apraxia of Speech: Effects of Noise Masking on Vowel Production
Journal of Speech, Language, and Hearing Research, April 2015, Vol. 58, 185-200. doi:10.1044/2014_JSLHR-S-13-0300
History: Received November 1, 2013 , Revised July 14, 2014 , Accepted October 29, 2014
 
Journal of Speech, Language, and Hearing Research, April 2015, Vol. 58, 185-200. doi:10.1044/2014_JSLHR-S-13-0300
History: Received November 1, 2013; Revised July 14, 2014; Accepted October 29, 2014
Web of Science® Times Cited: 4

Purpose This study was designed to test two hypotheses about apraxia of speech (AOS) derived from the Directions Into Velocities of Articulators (DIVA) model (Guenther et al., 2006): the feedforward system deficit hypothesis and the feedback system deficit hypothesis.

Method The authors used noise masking to minimize auditory feedback during speech. Six speakers with AOS and aphasia, 4 with aphasia without AOS, and 2 groups of speakers without impairment (younger and older adults) participated. Acoustic measures of vowel contrast, variability, and duration were analyzed.

Results Younger, but not older, speakers without impairment showed significantly reduced vowel contrast with noise masking. Relative to older controls, the AOS group showed longer vowel durations overall (regardless of masking condition) and a greater reduction in vowel contrast under masking conditions. There were no significant differences in variability. Three of the 6 speakers with AOS demonstrated the group pattern. Speakers with aphasia without AOS did not differ from controls in contrast, duration, or variability.

Conclusion The greater reduction in vowel contrast with masking noise for the AOS group is consistent with the feedforward system deficit hypothesis but not with the feedback system deficit hypothesis; however, effects were small and not present in all individual speakers with AOS. Theoretical implications and alternative interpretations of these findings are discussed.

Acknowledgments
This work was supported by New Century Scholars Research Grant from the American Speech-Language-Hearing Foundation, awarded to Edwin Maas, and National Institutes of Health Grants R01 DC007683 and R01 DC002852, awarded to Frank H. Guenther. Portions of these data have been presented at the International Conference on Speech Motor Control (Groningen, the Netherlands; June 2011), the Conference on Motor Speech (Santa Rosa, CA; March 2012), and the Clinical Aphasiology Conference (Tucson, AZ; May 2013). We thank Brad Story for his assistance with acoustic data analysis and his helpful comments on an earlier draft of this article; Tom Muller for his assistance in calibrating the masking noise; Gayle DeDe and Kimberly Farinella for their assistance in diagnosis; Pélagie Beeson, Janet Hawley, Fabiane Hirsch, and Kindle Rising for assistance with recruitment; Rachel Grief, Nydia Quintero, and Curtis Vanture for assistance with stimulus development; and Ashley Chavez, Lauren Crane, and Allison Koenig for their assistance with data collection and analysis. Finally, we thank our participants for their time and effort in supporting this research.
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