Fluency adaptation in speakers with Parkinson disease: a motor learning perspective

Fluency adaptation is characterised by a reduction in stuttering-like behaviours over successive readings of the same speech material and is an effect that is typically observed in developmental stuttering. Prominent theories suggest that short-term motor learning associated with practice explain, in part, fluency adaptation. The current investigation examined the fluency adaptation effect in a group of speakers with Parkinson disease (PD) who exhibited stuttering-like disfluencies.

Individuals with PD (n = 21) and neurologically healthy controls (n = 19) read a passage five times. Per cent syllables stuttered was measured and calculated for each reading passage.

Participants in the PD group exhibited significantly more stuttering-like disfluencies than control speakers. Twelve individuals in the PD group exhibited at least three per cent syllable stuttered on at least one reading. Statistical trends revealed that the subgroup of individuals with PD who stuttered exhibited a significant reduction in stuttering moments over the five successive readings.

A significant fluency adaptation effect was observed for the group of speakers with PD who exhibited stuttering-like disfluencies. Results of the current study are discussed within the framework of the motor learning hypothesis of fluency adaptation.