(AS1) Parkinson’s Disease Patients with Depression Have Decreased Caudate and Dorsolateral Prefrontal Cortex Beta Power Response to Positive Reinforcement

Introduction: Depression is a common nonmotor symptom of Parkinson’s Disease (PD) and is associated with impaired cognition. Decreased dopamine in PD elevates beta power in cortico-striato-thalamo-cortico (CSTC) motor circuits. Analogous dysfunction of parallel CSTC limbic and cognitive circuitry including the caudate and dorsolateral prefrontal cortex (DLPFC) may mediate nonmotor symptoms like depression and cognitive impairment. Previous studies have demonstrated that caudate and DLPFC beta power increases during positive feedback in a cognitive task and that PD cognitive impairment alters caudate and DLPFC beta power during working memory. Studies also show depression impairs learning from positive task feedback in PD patients. However, the relationship between beta power, depression, and cognition in PD remains unknown. We investigated whether working memory-related caudate and DLPFC beta power changes are altered in PD patients with depression.

Methods: Fifteen PD patients undergoing awake deep brain stimulation surgery with electrode trajectories traversing the caudate and/or DLPFC participated in this study. Subjects completed a 2-back working memory task where they identified whether a presented word matched the word presented two trials prior. Following response, subjects received visual feedback on whether they answered correctly. Subjects completed the Beck Depression Inventory-II (BDI-II) preoperatively, with a cut-off of 14 identifying patients with depression. Average beta power during feedback was compared between patients with and without depression using the Wilcoxon Rank-Sum test.

Results: Caudate and DLPFC beta power increased during feedback for correct trials. In both structures, this increase was significantly greater for subjects without depression compared to depressed subjects. DLPFC beta power during feedback negatively correlated with BDI-II score, with higher beta power corresponding with lower depression levels.

Conclusion : Depression is associated with reduced positive feedback-related corticostriatal beta power increase. These results suggest depression suppresses responsiveness to positive feedback during working memory, which may contribute to emotional and cognitive symptoms in PD patients with depression.