Download Parkinson`s Disease and the Effect of Lexical Factors on Vowel

Parkinson’s Disease and the Effect of Lexical Factors on Vowel Articulation
P.J. Watson, B. Munson
Vowels from infrequently used words and dense phonological neighborhoods are
produced at a larger distance from the center of their F1-by-F2 vowel space. It has been
hypothesized that these vowels are produced with larger dispersions to make them more distinct,
due to the fact these words are more difficult to recognize. Persons with Parkinson’s disease
(PD) produce vowels with smaller vowel space. However, it is unknown whether vowel
dispersion in relation to phonological neighborhood density (PND) and word frequency (WF) is
affected in PD, which might amplify any effect on reduced intelligibility.
Seven men with PD and 5 healthy men read words aloud while they were audio recorded.
CVC words were used as stimuli based upon their frequency of use and PND values. Acoustic
analysis was performed on the duration and Bark-scaled F1-F2 values of seven monophthongal
vowels contained in the words. Vowel-space dispersion was calculated from the centroid values
of each stimulus type.
Overall vowel-space dispersion was significantly smaller in the participants with PD in
relation to the control participants. Vowel space was significantly less expanded for lowfrequency high-density words in the PD talkers. Moreover, vowel space was significantly less
expanded for all low-frequency words in persons with PD.