External cueing facilitates auditory-motor integration for speech control in individuals with Parkinson's disease

Instructing individuals with Parkinson's disease (PD) to speak loudly and clearly with external cues leads to improvements of their speech in loudness, pitch, and articulatory movement, but the underlying neural mechanisms are largely unknown. The present event-related potential study investigated whether and how external cueing can facilitate auditory-motor control of speech production in PD. Individuals with PD and healthy controls produced sustained vowels with internal and external auditory cues while hearing their voice pitch-shifted -200 cents. Individuals with PD produced significantly larger vocal compensations than healthy controls in the internally cued condition and exhibited a significant decrease in the magnitudes of vocal compensations with external cueing. Moreover, individuals with PD produced significantly smaller N1 responses and larger P2 responses in the externally versus internally cued condition and exhibited a significant correlation between decreased vocal compensations and increased P2 amplitudes after external cueing. These findings provide the first neurobehavioral evidence that external auditory cueing can compensate for impaired auditory-motor processing of vocal feedback errors associated with PD in a top-down manner.