Masters Theses

Date of Award

6-1983

Degree Type

Thesis

Degree Name

Master of Arts

Major

Speech Pathology

Major Professor

Ellen I. Hamby

Committee Members

Carl W. Asp, Harold L. Luper

Abstract

The purpose of this investigation was to examine the differences in voice onset times (VOTs) for the consonants /b/,/p/,/g/, and /k/ among ten speakers with Parkinson's disease and dysarthria (PKN-D), ten speakers with Parkinson's disease and no observable dysarthria (PKN-NOD), and ten normal speakers (NOR). The subjects were asked to repeat the sentence "Say___again" after the examiner who varied the stimuli /bip/,/pip/,/gip/, and /kip/ until five repetitions of each stimulus were obtained. The responses were played into a Voice Identification Unit (Voice Identification, Inc., Series 700) and spectrograms were made. VOTs for the stimuli /b/,/p/,/g/, and /k/ were determined from the spectrograms.

Statistical analyses involved obtaining individual subjects' mean VOTs for all four consonants, group means and ranges for each of the four consonants, a total mean VOT for each group across all four consonants, and mean VOTs for each consonant across all three groups. A two factor mixed design analysis of variance with repeated measures on one factor (Bruning and Kintz, 1977) was used to determine whether statistically significant differences existed among the three groups of subjects and among the VOTs for the four different consonants. The results of the analysis of variance indicated that there were significant differences in VOTs among the consonants /b/,/p/,/g/, and /k/. The Scheffe test for multiple comparisons (Bruning and Kintz, 1977) was utilized to determine between which groups of speakers significant differences existed across the four consonants. The results of the Scheffe'' revealed that there were significant differences in VOTs between the speakers with Parkinson's disease and dysarthria and the normal speakers for every consonant. In addition, the Scheffe'' revealed a significant difference in VOTs between the PKN-NOD speakers and the NOR speakers for /k/, and between the PKN-D and the PKN-NOD speakers for /p/.

The findings of this investigation suggest that dysarthric speakers with Parkinson's disease do have incoordination of their phonatory and articulatory movements. Secondly, the findings partially support the hypothesis that the deterioration of speech in individuals with Parkinson's disease begins with laryngeal changes and progresses forward in the vocal tract affecting the tongue and then the lips. Finally, the results of this investigation indicate that voice onset time might be used to detect an emerging dysarthria in speakers with Parkinson's disease and no observable dysarthria. However, much more research is needed to provide additional information about the onset and progression of dysarthria in individuals with Parkinson's disease.

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