Alterations of regional homogeneity in Parkinson's disease with "pure" apathy: A resting-state fMRI study

Background: Apathy is a prevalent and debilitating neuropsychiatric syndrome in Parkinson's disease (PD). However, its neural mechanisms are still unclear. Methods: Forty-six de novo, drug-naive, non-demented PD patients without depressive or anxious symptoms, of whom 26 were apathetic (PD-A) and 20 were not (PD-NA) according to the Apathy Scale (AS), and 23 matched healthy control (HC) subjects were enrolled in this study. The regional homogeneity (ReHo) approach based on resting-state functional MRI on a 3-T MR system was used to investigate apathy related local brain activity. Results: Compared with both patients with PD-NA and HC subjects, patients with PD-A showed signi ficantly lower ReHo values in the dorsal anterior cingulate cortex (ACC) and right caudate. Both the PD-A and PD-NA groups also demonstrated lower ReHo values in the right putamen compared to the HC group. Further corre- lation analyses revealed that AS scores were negatively correlated with the ReHo values in the dorsal ACC and right caudate in the pooled patients with PD. Limitations: The present results are preliminary due to the small sample size in the study. Conclusions: This study used ReHo for the first time to characterize "pure " apathy related regional spontaneous brain function within the frontostriatal circuits in PD. Our findings suggest that abnormal brain activity in the dorsal ACC and caudate may involve the pathological mechanisms of apathy in PD.