Correlation between vowel centralisation and incomplete stop articulation in individuals with traumatic brain injury

Traumatic brain injury (TBI) often results in dysarthria, a motor speech disorder. Two processes often linked with TBI dysarthria are vowel centralisation and incomplete stop articulation. It is not clear to what extent these two processes are interrelated and to what extent they might serve as indices of the severity of dysarthria secondary to TBI. The purpose of this study is to test the hypothesis that patients who centralise vowels will also have difficulties producing stop consonants with complete stricture. Polish dysarthric speakers post TBI (n=6) and ten age-matched healthy controls with normal speech (n=10) performed the Polish Dysarthria Test for TBI Patients (PDTTP) (Połczyńska-Fiszer and Pufal 2006). Three of the TBI subjects had moderate dysarthria and three mild dysarthria. The test investigates phonemes in isolation as well as in diverse phonetic contexts in different elicitation tasks, including spontaneous speech. The data from the PDTTP were transcribed phonetically and analysed acoustically. Vowel centralisation and incomplete stop articulation appear to be strongly correlated (r=0.90). It was found that the degree of TBI dysarthria correlates with the frequency of occurrence of these two processes. Thus, the two processes may serve as important indices of severity of dysarthria in TBI.