Reward learning deficits in Parkinson's disease depend on depression

BACKGROUND: Depression is one of the most common and debilitating non-motor symptoms of Parkinson's disease (PD). The neurocognitive mechanisms underlying depression in PD are unclear and treatment is often suboptimal.

METHODS: We investigated the role of striatal dopamine in reversal learning from reward and punishment by combining a controlled medication withdrawal procedure with functional magnetic resonance imaging in 22 non-depressed PD patients and 19 PD patients with past or present depression.

RESULTS: PD patients with a depression (history) exhibited impaired reward v. punishment reversal learning as well as reduced reward v. punishment-related BOLD signal in the striatum (putamen) compared with non-depressed PD patients. No effects of dopaminergic medication were observed.

CONCLUSIONS: The present findings demonstrate that impairments in reversal learning from reward v. punishment and associated striatal signalling depend on the presence of (a history of) depression in PD.