Semantic and Phonological Encoding Times in Adults Who Stutter: Brain Electrophysiological Evidence Purpose Some psycholinguistic theories of stuttering propose that language production operates along a different time course in adults who stutter (AWS) versus typically fluent adults (TFA). However, behavioral evidence for such a difference has been mixed. Here, the time course of semantic and phonological encoding in picture naming was compared ... Research Article
Research Article  |   October 17, 2017
Semantic and Phonological Encoding Times in Adults Who Stutter: Brain Electrophysiological Evidence
 
Author Affiliations & Notes
  • Nathan D. Maxfield
    Department of Communication Sciences and Disorders, University of South Florida, Tampa
  • Disclosure: The author has declared that no competing interests existed at the time of publication.
    Disclosure: The author has declared that no competing interests existed at the time of publication. ×
  • Correspondence to Nathan D. Maxfield: nmaxfield@usf.edu
  • Editor: Julie Liss
    Editor: Julie Liss×
  • Associate Editor: Hans-Georg Bosshardt
    Associate Editor: Hans-Georg Bosshardt×
Article Information
Speech, Voice & Prosodic Disorders / Fluency Disorders / Speech, Voice & Prosody / Language / Research Articles
Research Article   |   October 17, 2017
Semantic and Phonological Encoding Times in Adults Who Stutter: Brain Electrophysiological Evidence
Journal of Speech, Language, and Hearing Research, October 2017, Vol. 60, 2906-2923. doi:10.1044/2017_JSLHR-L-16-0309
History: Received August 1, 2016 , Revised April 7, 2017 , Accepted June 11, 2017
 
Journal of Speech, Language, and Hearing Research, October 2017, Vol. 60, 2906-2923. doi:10.1044/2017_JSLHR-L-16-0309
History: Received August 1, 2016; Revised April 7, 2017; Accepted June 11, 2017

Purpose Some psycholinguistic theories of stuttering propose that language production operates along a different time course in adults who stutter (AWS) versus typically fluent adults (TFA). However, behavioral evidence for such a difference has been mixed. Here, the time course of semantic and phonological encoding in picture naming was compared in AWS (n = 16) versus TFA (n = 16) by measuring 2 event-related potential (ERP) components: NoGo N200, an ERP index of response inhibition, and lateralized readiness potential, an ERP index of response preparation.

Method Each trial required a semantic judgment about a picture in addition to a phonemic judgment about the target label of the picture. Judgments were mapped onto a dual-choice (Go–NoGo/left–right) push-button response paradigm. On each trial, ERP activity time-locked to picture onset was recorded at 32 scalp electrodes.

Results NoGo N200 was detected earlier to semantic NoGo trials than to phonemic NoGo trials in both groups, replicating previous evidence that semantic encoding generally precedes phonological encoding in language production. Moreover, N200 onset was earlier to semantic NoGo trials in TFA than in AWS, indicating that semantic information triggering response inhibition became available earlier in TFA versus AWS. In contrast, the time course of N200 activity to phonemic NoGo trials did not differ between groups. Lateralized readiness potential activity was influenced by strategic response preparation and, thus, could not be used to index real-time semantic and phonological encoding.

Conclusion NoGo N200 results point to slowed semantic encoding in AWS versus TFA. Discussion considers possible factors in slowed semantic encoding in AWS and how fluency might be impacted by slowed semantic encoding.

Acknowledgments
This research was supported by the National Institutes of Health–National Institute of Deafness and Other Communication Disorders under Grant R03DC011144 awarded to Nathan Maxfield. I am grateful to Kalie Morris, Kade Jentik, Kathryn Morphew, and Alissa Belmont for their efforts in collecting and processing the data presented here. Participation of adults who stutter is greatly appreciated. Finally, I am grateful to Valerie Shafer, Arild Hestvik, Helen Cairns, and Ben Watson for their support in early stages of development of this research.
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