Perception of speech rate and intensity in Parkinson's disease

Purpose: Parkinson's disease (PD) is a neurodegenerative disease that affects motor control but can also influence sensory perception. Changes in vision and proprioception are well-documented but less is known about how PD alters auditory perception, particularly perception of speech acoustic properties. The current study examined perception of speech rate and intensity in PD and the relationship of auditory perception to disease severity. Method: People with PD were compared to age- and hearing-matched controls using perceptual tasks focused on discrimination and learning of speech rate and intensity. For rate discrimination, speech, non-speech, and visual stimuli were included to determine whether performance differences for PD participants and controls were specific to speech. Disease severity was assessed using the MDS-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and the relationship to performance on perceptual discrimination and learning tasks was evaluated. Results: People with PD performed significantly worse than controls in the rate discrimination task for all types of stimuli. There were no significant group differences for intensity discrimination. However, participants with greater PD disease severity demonstrated significantly poorer intensity discrimination accuracy. Performance on learning tasks utilizing rate and intensity manipulations did not differ between PD and control participants and was unrelated to PD disease severity. Conclusions: People with PD had difficulty discriminating rate differences across speech, non-speech, and visual stimuli, indicating that challenges with rate perception are not limited to speech. The relationship between intensity discrimination and disease severity may suggest common dopaminergic networks between motor symptoms and auditory perception in PD.