Graduation Year

2009

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Speech-Language Pathology

Major Professor

Nathan D. Maxfield, Ph.D.

Keywords

Event-related potentials, Psycholinguistic, Lexical, Adults

Abstract

To date, research on mechanistic aspects of fluency disorders has focused heavily on motor contributions to stuttering. Only recently have researchers begun to explore psycholinguistic contributions to stuttering. Psycholinguistic planning for speech heavily involves the activation and processing of lexical information. We used a neuroscience approach to compare word activation in mental lexicon while completing a picture naming task in people who stutter (PWS) versus fluent individuals (PWNS). Twenty-eight individuals ranging in age from 19 - 52 years old participated in a picture-word priming task adopted from Jescheniak et al. (2002). Electroencephalogram (EEG) was recorded while participants saw black and white line drawings, followed immediately by an auditory probe word that was either Semantically-Related, Phonologically-Related, or Unrelated to the label of the preceding picture. EEG was also recorded to Filler (naming-only) trials.

Averaged ERPs were generated for each condition. Two principal component analyses (PCA) were conducted in order to summarize patterns in the ERP data and test for differences in ERPs elicited by different conditions. One PCA compared Semantically-Related probe word trials, Semantically-Unrelated probe word trials, and Filler trials. The second PCA compared Phonologically-Related probe word trials, Phonologically-Unrelated probe word trials, and Filler trials. The primary goal of each analysis was to determine whether each probe word condition elicited ERP activity that was different from Filler (naming-only) trials. Relative to Filler trials, all four types of probe words elicited a series of ERP components, some related to sensory processing of the probe words, and some related to linguistic processing of the probe words including N400-type ERP activity. Crucially, N400 priming was observed for PWNS on Semantically-Related trials, but not for PWS.

This result indicates that the activation of semantic word networks on the path to picture naming may operate differently in PWS versus PWNS. In contrast, no differences were found between groups for Phonological N400 priming. Discussion relates these effects to the larger body of existing literature on psycholinguistic ability in PWS. Discussion also focuses on how the activation of semantic word networks may differ in PWS versus PWNS, and how therapy for stuttering might address such differences.

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