Hippocampal functional connectivity-based discrimination between bipolar and major depressive disorders

Despite the impressive advancements in the neuropathology of mood disorders, patients with bipolar disorder (BD) are often misdiagnosed on the initial presentation with major depressive disorder (MDD). With supporting evidence from neuroimaging studies, the abnormal functional connectivity (FC) of the hippocampus has been associated with various mood disorders, including BD and MDD. However, the features of the hippocampal FC underlying MDD and BD have not been directly compared. This study aims to investigate the hippocampal resting-state FC (rsFC) analyses to distinguish these two clinical conditions. Resting-state functional magnetic resonance imaging (fMRI) data was collected from a sample group of 30 patients with BD, 29 patients with MDD and 30 healthy controls (HCs). One-way ANOVA was employed to assess the potential differences of the hippocampus FC across all subjects. BD patients exhibited increased FC of the bilateral anterior/posterior hippocampus with lingual gyrus and inferior frontal gyrus (IFG) relative to patients MDD patients. In comparison with HCs, patients with BD and MDD had an increased FC between the right anterior hippocampus and lingual gyrus and a decreased FC between the right posterior hippocampus and right IFG. The results revealed a distinct hippocampal FC in MDD patients compared with that observed in BD patients. These findings may assist investigators in attempting to distinguish mood disorders by using fMRI data.