Altered Timing of Self-Voice Processing in Parkinson's Disease.

Parkinson's disease (PD) affects voice and speech production, often resulting in reduced vocal intensity and monotonous speech. Recent studies suggest that these changes can be partially explained by altered sensory feedback processing in speech production: individuals with PD (IwPD) may fail to monitor and adapt sensory feedback when producing speech. We investigated PD voice production using a voice playback paradigm and focused on the sensory attenuation typically observed in event-related responses (ERPs) to the self-generated voice. When sensory feedback is intact, the P50, N100, and P200 responses to a self-generated voice are attenuated compared to an externally generated voice. Twenty-three IwPD and 23 matched healthy controls (HCs) completed the voice playback study with three conditions: self-generated voice (auditory-motor [AMC]), externally generated voice (auditory-only [AOC]), and motor-only. Linear mixed models assessed group differences in ERP morphology. Groups differed in the N100 latency response: IwPD showed a greater shift in latency between AMC and AOC than healthy controls. Regarding the P200, a significant group-by-condition interaction indicated that IwPD, unlike healthy controls, produced larger amplitudes for the self-generated than the passively listened to voice. Taken together, these findings suggest that the processing of one's own voice in IwPD is altered in terms of temporal precision rather than in the N100 suppression effect per se. This effect was accompanied by an enhanced P200 attentional response. These response patterns in IwPD are indicative of likely progressing difficulties in regulating one's own voice, characteristic of Parkinson's disease.