Objective This study used resting-state functional MRI (fMRI) to evaluate regional and network alterations in patients with Parkinson's disease (PD) with and without depression.

Method We recruited 29 patients with PD with depression (PD-Dep), 30 patients with PD without depression (PD-NDep), and 30 normal controls. All participants underwent resting-state fMRI scans on a 3-T MR system. The amplitude of low-frequency fluctuation (ALFF) of blood oxygen level-dependent signals was used to characterise regional cerebral function. Functional integration of the brain network was evaluated by seed-based correlation approach.

Results The PD-Dep group showed significantly higher ALFF value in the left orbitofrontal area compared with both the PD-NDep and control groups (p<0.05 corrected by FWE). In patients with PD, the Hamilton Depression Rating Scale score was positively correlated with the ALFF value in the left orbitofrontal cortex (p<0.005 uncorrected). Brain network connectivity analysis revealed reduced functional connectivity of putamen in both PD subgroups. However, the PD-Dep group showed more distributed reduced connectivity in the prefrontal-limbic network than the PD-NDep group did (p<0.05 corrected by FWE).

Conclusions Our study demonstrates that PD-Dep patients are characterised by increased regional spontaneous neural activity in the orbitofrontal area and decreased functional integration within the prefrontal-limbic network. These findings may be helpful for facilitating further understanding of the potential mechanisms underlying depression in PD.