P300 Event-Related Potential: A Surrogate Marker of Cognitive Dysfunction in Parkinson's Disease Patients with Psychosis.

BACKGROUND AND OBJECTIVES: Psychosis is one of the major neuropsychiatric non-motor symptoms of Parkinson's disease (PD). Prolonged latency and decreased amplitude of the P300 event-related potential (ERP) is a potential neurophysiologic biomarker of deeper neurocognitive deficits in PD. We aimed to characterize electroencephalogram (EEG)/ERP parameters in PD patients with and without psychosis (PDP and PDNP, respectively), and to determine if such measures could act as endophenotypes for PD-associated psychosis (PDP). METHODS: We recruited 40 PD patients (all males), 20 PDP patients and 20 PDNP patients, aged between 39 and 65 years. The cognitive composite scores for attention and working memory were calculated. EEG/ERP recording was carried out following this, with eyes-closed resting-state EEG followed by an auditory oddball P300 task. RESULTS: The composite scores for both attention and working memory were significantly higher in the PDNP group compared to the PDP group. The mean reaction time during the oddball task in the PDP group was significantly higher than in the PDNP group. A trend of increased P300 amplitude was observed in the PDNP group compared to the PDP group; however, it was significant at CP4, P8, C4, TP8, T8, CZ, FC4, FT8, FZ, F4, and F8 electrode sites. Power spectral analysis indicated a significant increase in the EEG power of slow-frequency waves (delta, theta) across all the brain regions in the PDP group compared to the PDNP group. CONCLUSIONS: Our results demonstrate the association between psychosis and the severity of neurocognitive deficits in PD patients assessed using electrophysiologic measures. P300 may be considered a potential neurophysiologic biomarker of psychosis in PD.