Sensory Feedback in Parkinson Disease Voice Production: A Systematic Review

BACKGROUND: Understanding voice and speech impairments in Parkinson's disease (PD) is essential for developing effective interventions and ensuring efficient social communication. OBJECTIVE: This review reports findings on voice perception and production in PD with a specific focus on sensory feedback (auditory and somatosensory) of the self-voice, neural correlates of the voice, and voice quality parameters such as pitch, loudness, and emotion modulation. METHODS: A combined bibliometric analysis and a systematic review should identify key trends and knowledge gaps in the neuroimaging (functional magnetic resonance imaging (fMRI)/EEG) literature on PD self-voice processing. RESULTS: EEG studies focusing on pitch revealed significant differences in the P200 event-related potential, but no differences in the N100, between healthy controls and individuals with PD. fMRI studies showed reduced activation in the motor cortex and basal ganglia during speech production in PD, accompanied by increased activation in other brain regions, such as the auditory cortex, which was associated with pitch variability and loudness control. A decrease in right dorsal premotor cortex activation was linked to impaired voice control, particularly regarding loudness modulation. Additionally, the review identified missing research on the emotion modulation of the voice, despite its critical role in social communication. Altered sensory feedback plays a significant role in compensatory cortical responses during vocalization, underscoring the importance of sensory feedback in maintaining normal voice production in PD. CONCLUSIONS: This review identified missing research on voice loudness perception and the potential impact of emotion perception deficits regarding voice modulation in persons with PD.