Variability Within and Across Physiological Systems in Dysarthria

M McHenry


There are many sources of variability within the speech production system.It is not known if variability within a system is associated with variability across physiological systems.In this investigation, eight individuals with dysarthria repeated an utterance in four speaking conditions.The spatio-temporal index (STI), a composite measure of spatial and temporal variability taken across token repetitions, was derived from the movement of the lower lip.To assess variability across physiological systems (i.e., respiratory, laryngeal, articulatory), voice onset time (VOT) was calculated for each participantís least and most variable utterances.The coefficient of variation (COV) of VOT was taken as a measure of variability across physiological systems.There was a significant difference in STI between low and high variability conditions.There was no difference in VOT COV between the two conditions.Further, there was no relationship between VOT COV and STI.It was concluded that there is no relationship between variability within a single physiological system (i.e., articulatory) and variability across physiological systems (as represented by VOT COV).The implication of these findings, as well as challenges in measuring VOT in dysarthria, will be discussed.