Vowel space in hypokinetic dysarthria

Abstract

The paper discusses acoustic and articulatory data on the use of vowel space by speaker affected by Parkinson’s Disease who developed hypokinetic dysarthria. Two experiments involving pathological subjects and matching controls are described, whose general aim is to better understand if the vowel space in Parkinson’s Disease dysarthric subjects is always and homogeneously reduced. In the first investigation, acoustic and kinematic data are collected and analyzed to test if pathological speakers always use a reduced vowel space compared to control subjects, and if they adopt different articulatory strategies depending on the axis of the speech gesture (vertical vs horizontal). In the second investigation, various articulatory metrics are used to better investigate the dimension and position of the acoustic vowel space, and if they change in Parkinson’s Disease subjects compared to controls. Results show that reduction takes place, but some subjects appear to compensate, widening their tongue gestures on the horizontal axis even though the lip gesture is not necessarily undershot. Nevertheless, metrics used in the second experiment do not allow to capture a reduction, even though, in line with results of the first experiment, they point to an asymmetry in the vowel space used depending on the axis considered.