Parkinson’s Disease and Communication: Intelligibility, Interaction and Participation

Parkinson’s disease is a neurodegenerative disorder affecting dopamine production in the basal ganglia. It is a common cause of disability among elderly people. The main symptoms are tremor, rigidity, and bradykinesia, but there is a substantial individual variation of how the disease manifests itself. Communicative changes occur frequently and motor speech impairment in the form of dysarthria is common. Other communicative abilities, such as language functions and the use of body gestures, may also be affected. Traditionally, the focus for research and clinical assessments and interventions in the context of communicative changes in Parkinson’s disease has mainly been on speech and voice impairment. However, the impact on communication is multi-faceted, and different factors may affect the ability to make oneself understood and participate in conversations. Conversation is also a collaborative activity, where all participants’ contributions would need to be considered. Although there is a growing body of research on communicative impact in Parkinson’s disease, these aspects have, so far, been less studied. In the present thesis, communicative changes in Parkinson’s disease were explored with a focus on speech intelligibility, interaction in conversations, and communicative participation. In study I, qualitative interviews with dyads consisting of a person with Parkinson’s disease and a close communication partner revealed individual variation in experiences of communicative changes. The results indicated multi-factorial disease-related impact on everyday communication and communicative participation. A change noted in almost all dyads was that the partner with Parkinson’s disease participated less in conversations. In study II, listener ratings of connected speech intelligibility showed both inter- and intra-speaker variability between different types of assessment tasks, indicating that di-verse factors may influence intelligibility for individual speakers. Listener knowledge of context significantly increased intelligibility scores. Acoustic analyses of consonant articulation in study III indicated that some measures may be more sensitive for detecting impact on speech and intelligibility for speakers with Parkinson’s disease, while other aspects of articulation may be demanding in terms of acoustic realisation also for healthy elderly speakers. Visual examination of spectrograms may provide qualitative information about speech production in relati