Parkinson's disease (PD) is characterized by the degeneration of nigrostriatal dopaminergic neurons, resulting in dysfunctional cortico­-striato-­thalamic­cortical loops. Parkinson's disease patients suffer from chronic movement disabilities as well as cognitive impairments and other nonmotor symptoms, which implies a system­wide effect on overall brain function. Because the disease currently has no cure, the discovery of a biomarker for specific PD symptoms is crucial for monitoring treatment potency. This study aimed to evaluate the validity of using functional connectivity between regions of the basal ganglia as a biomarker for specific symptoms of PD.