Emotional and cognitive processing in Parkinson's disease

• ¹ The University of Queensland Centre for Clinical Research and RBWH, UQ Centre for Clinical Research, Australia
• ² Royal Brisbane & Women's Hospital, Neurology Research Centre, Australia
• ³ The University of Queensland Centre for Clinical Research and RBWH, School of Health & Rehabilitation Sciences, Australia
• ⁴ The University of Queensland Centre for Clinical Research and RBWH, School of Medicine, Australia
• ⁵ Royal Brisbane & Women's Hospital, Department of Psychiatry, Australia
• ⁶ Griffith University , Eskitis Institute for Cell & Molecular Therapies, Australia

Background: Emotional dysfunction and cognitive impairment are frequent non-motor complications in Parkinson's disease (PD). Over 50% experience anxiety and depression, 25% experience mild cognitive impairment (MCI), and a further 25% experience dementia at end stage PD. However, mechanisms underpinning these neuropsychiatric disturbances in PD are poorly understood. This study aims to identify event related potentials (ERPs) associated with cognitive and affective processes in PD. Methods: Fifty three (53) PD patients completed a visual word affective priming task while ERPs were recorded. The task presented negative or neutral word pairs with a stimulus onset asynchrony of 250ms. Participants evaluated the valance of the second word (target word). Repeated measures ANOVAs were used to investigate the effects of Target Valence and Congruency on P3 and LPP ERP amplitudes. We also investigated the interactions between these factors and depression, anxiety and cognitive rating scale scores using covariance and subsequent partial correlations. Results: P3 and LPP amplitude deflections were larger for negative targets compared to neutral targets at Pz electrode (P3 F=6.82, p=0.01; for LPP F=5.88, p=0.01). Target valence X Congruency X Covariate interactions were observed for depression (P3 F=7.8, p<0.01; LPP F=4.30, p=0.04) and cognitive impairment (P3 F=10.3, p<0.01, LPP F=5.84, p=0.01). The P3 difference wave (incongruent - congruent) for neutral targets positively and independently correlated with depression (r=0.39, p=0.005) and cognitive impairment (r=0.33, p=0.02). Similarly, the LPP difference wave for neutral targets positively correlated with depression when adjusted for cognitive impairment and anxiety (r=0.35, p=0.02). Conclusion: P3 and LPP allow discrimination of negative biases associated with stimulus processing. These results demonstrate that depression and cognitive impairment independently influence the processing of negative prime words in PD.