Disfluency and speech management in Italian patients with early-stage Parkinson's Disease

Parkinsonian speech has often been described as "disfluent". However, the specific nature of disrupted speech in Parkinson’s Disease (PD) patients has not been well observed. Considering that pauses, fillers, repetitions and self-repairs are commonly used in spontaneous speech for managing and monitoring the own speech production, this study aims at investigating the characteristics of disfluency phenomena patterns in early-stage PD subjects. To reach this goal, the monological speech of 18 PD patients and 18 age- and sex-matched healthy subjects, all Italian native speakers, was annotated distinguishing between Forward-Looking Disfluencies, such as silent pauses, lexical and non-verbal fillers and prolongations, through which message delivery is suspended for planning, and Backward-Looking Disfluencies, such as repetitions, insertions, deletions and substitutions, used by the speaker to edit something already uttered. Pathological and healthy speech samples were compared with reference to four parameters: the number and frequency of disfluencies; their specific functions; the syntactic positioning of the items; the duration of silent pauses, filled pauses and lengthening. Results highlight the relevance of investigating the specific uses, types and characteristics of disfluency phenomena rather than just considering their frequency of occurrence to gain insight into the features of Parkinsonian speech, even at a very early stage.