The investigation of the neural signature of reward processing in Parkinson's patients through EEG (electroencephalogram)

Objective: Parkinson's Disease (PD) is a progressive neurodegenerative disorder primarily affecting dopaminergic neurons in the substantia nigra, leading to dysfunction in reward processing. Reward processing plays a critical role in daily life and is associated with neuropsychiatric disorders and symptoms in PD. Due to its multifaceted nature, studying various dysfunctional manifestations of reward processing in PD is important. Method: Several studies have proposed the presence of event-related potential (ERP) component manifestations in PD patients during reward processing. This study investigates reward processing paradigms in PD patients using electroencephalography (EEG) during a novel behavioral paradigm that combines a go/no-go task with reward-expectation manipulation and varying feedback in the form of monetary reward or loss. I analyzed ERP in response to feedback, focusing on the feedback-related negativity (FRN) component. Results: Conducting a mixed ANOVA design (2x2) revealed that neither the group factor (patient & control) nor the condition factor (differential between win and lose in high expectation condition, and differential between win and lose in low expectation condition) had a significant main effect on mean amplitude and peak amplitude. However, a significant interaction effect between the group and condition factors was found for peak amplitude. Further post-hoc (Tukey's HSD) analysis revealed there is a significant difference between the groups win and lose differential for high expectation group and win and lose differential for low expectation group in PD people. Conclusion: This study provides insights into the neural correlates of reward processing dysfunction in PD patients, highlighting the importance of studying the various aspects of reward processing to better understand the disorder. The findings suggest that PD patients may exhibit distinct reward processing patterns related to expectation levels, which could potentially inform the development of targeted therapeutic interventions and contribute to a better understanding of neural dynamics in PD. Moreover, the lack of significant differences in FRN amplitude between the two groups in the present study, along with inconsistent findings in this area regarding reward expectation and valence, underscores the need for further research.