Consonant distortions in dysarthria due to parkinson's disease, amyotrophic lateral sclerosis and cerebellar ataxia

This paper addresses the presence and type of consonant distortions in speech of 79 French speakers with dysarthria due to Parkinson’s disease (PD), Amyotrophic Lateral Sclerosis (ALS) and cerebellar ataxia (CA), and 26 control speakers. A total of 4990 consonants including selected occurrences of /d/, /g/, /t/, /k/ and /s/ in CV word-initial syllables, and /t/ in CV word medial and IP initial position were examined manually. Results show that the ALS group stands out with the more distorted consonants, while the PD and CA performed similarly. The distribution of the type of distortions differs also in the three dysarthric groups. While the most frequent type of distortion in ALS is incomplete closures of stops, devoicing of voiced consonant is the most frequent in the PD and CA groups. In the ALS group, distortions are also more uniformly distributed over consonant type and positions, while voiced consonants are more prone to distortion in PD and CA, as well as consonants in word medial position for PD. Finally, consonant distortions contribute strongly to perceived intelligibility and articulatory imprecision for the ALS and PD group.