Vowel Articulation Index and Conversational Spontaneous Speech Intelligibility in Parkinson's Disease.

Abstract

By Maria Molett, Communication Sciences and Disorders

Advisor: Carrie Rountrey

Abstract: Purpose: In Parkinson's Disease (PD), Vowel Articulation Index (VAI) has been shown to be related to elicited speech intelligibility (ESI). VAI derives from F1 and F2 of the corner vowels /i/, /u/, and /a/, and is sensitive to mild hypokinetic dysarthria in PD. However, this effect has not been investigated in conversational spontaneous speech intelligibility (SSIC), which is the objective of this study. Methods:_A pilot study was conducted with_9_participants_with PD (7M, 2F,___=67)_with mild to moderate speech impairment due to dysarthria. Participants wore a recording device while in the lab, capturing conversation. Ten sentences were randomly selected. Three novel listeners transcribed each sentence; these transcriptions were compared to a key for SSIC (% words intelligible). Mean SSIC (__SSIC) for each participant was calculated. Mean VAI in conversation (__VAIC) was calculated for each participant and compared to __SSIC. Results:____SSIC_increased_by 10%_for each .148 unit increase in___VAI._Regression power calculation_=_0.13,_5% significant level,_effect size of 0.1_for this initial_subset._To achieve_.80 power, 80 participants would be needed._ Conclusion:_In the first known study of_its_kind,___VAIC_is regressed against___SSIC_in conversational speech in the lab environment. Power in this sample is thought to be limited by the heterogeneity of participants with mild-moderate speech impairment. Still, a clinically significant increase in __SSIC is noted, as __VAIC increases. Continued study of VAI as a correlate to conversational SSI is worthwhile for ecological validity.