Clinical Utility of the Vocal and Speech Reaction Time Task in the Evaluation of Patients with Dysphonia

Introduction: Differential diagnosis of dysphonic patients without laryngeal lesions may not be easy when voice production difficulties are found under certain conditions. The aim of this study was to determine whether there are quantitative or qualitative differences between normal speakers and dysphonic patients in their responses to a reaction time (RT) task. Method: Ten patients with spasmodic dysphonia (SD) and ten normal speakers participated in the study. We used three test tokens: open vowel /a/ and two words that differed in the voicing, /ame/ and /hai/. Each speaker was instructed to produce one of the tokens immediately after an auditory stimulus. Five trials of each token were performed under two loudness conditions. In addition to the perceptual analysis, an acoustic analysis was performed to measure response latency, token duration, and fo mean and range. A three-factor analysis of variance (ANOVA) with repeated measures on two factors, Group by (Loudness by Token), was performed on two measures (response latency and token duration). Results: Response latency was overall longer in SD than in Control for both normal and loud conditions. Response latency was longer for SD than for Control, and a main effect of token was significant (F=10.56, df=2, 18). A non-significant but notable token by group interaction was found. Response latency was longer for /ame/ for SD. Token duration was longer for loud voice than for normal voice, and longer for /ame/ than for /hai/ and /a/. The main effects of loudness and token were significant (loudness: F=17.38, df=1.18, token: F=55.70, df=2.18). Acoustic changes corresponding to voice breaks, such as reduced fo and intensity, were identified. Quantitative and qualitative assessment is an important indicator for detecting dysphonia in RT tasks.

Conclusions: The RT task is a stress test of voice and speech production; with carefully chosen test tokens and speaking conditions, it has a potential clinical utility in the differential diagnosis of dysphonia with functional components.