Perception and Production of Speech Timing in Parkinson's Disease

Project Summary: Parkinson’s disease (PD) is the second-most common neurodegenerative disease and results in hypokinetic dysarthria in as many as 90% of individuals, leading to negative mental health outcomes and reduced quality of life. Although current pharmacological and neurosurgical treatments are effective at treating gross motor challenges, they do not adequately address speech symptoms. Improving understanding of the underlying pathophysiology of speech disturbance in PD and factors affecting its variability is critical for developing individualized treatments that optimize outcomes. Among the most distinctive features of hypokinetic dysarthria in PD are abnormalities in the timing of speech production, characterized by fast or slow rate, intermittent rushes of speech, increased or decreased pause time, and increased disfluencies. These features are notably variable across individuals. People with PD also demonstrate deficits in timing perception including a reduced ability to discriminate short-duration auditory stimuli and beat-based rhythms. Considering these motor and sensory timing impairments in PD and the importance of sensorimotor integration in speech, impaired perception of speech timing may contribute to or exacerbate difficulties in speech timing production in this population. However, there are significant knowledge gaps regarding the speech timing perception abilities of people with PD and the relation between perception and production for speech timing in this population. This project will address these gaps through two specific aims. Aim 1 will comprehensively test speech timing acuity in individuals with PD, examining acuity for rate, rhythm, and segment duration using both speech and non-speech stimuli. We hypothesize that, similar to how they perform on non-speech timing acuity tasks, individuals with PD will have reduced acuity for detecting differences in these speech timing parameters. Aim 2 will examine the relationship between perceptual timing acuity and speech production timing in people with PD to examine the hypothesis that altered speech perceptual acuity can explain variability in the timing of speech production. Results will both inform the potential role of altered timing perception in the communication challenges of people with PD and provide a potential explanation for the wide variability in the timing speech production in PD. Furthermore, these studies will serve as a launchpad to explore the neural and behavioral mechanisms underlying speech timing variability in PD and support the development of novel speech interventions to adequately address speech timing challenges.