The dynamic functional connectivity of the left rostral hippocampus involved in mediating the association between hippocampal volume and antidepressant efficacy in major depressive disorder

Abstract

Abstract The hippocampus is highly involved in the pathophysiology of major depressive disorder (MDD), indicating some changes in hippocampal structure and function during MDD condition and also due to antidepressant treatment. However, it is unclear whether structure factors of the hippocampus can effectively impact antidepressant responses by hippocampal functional activity in MDD patients. The longitudinal data were collected from 36 MDD patients before and after 3 months of antidepressant pharmacotherapy. Baseline data from 43 sex- and age-matched healthy controls were also acquired. The dynamic functional connectivity (dFC) of the hippocampal subregions was estimated via a sliding-window method based on resting-state functional magnetic resonance imaging (rs-fMRI). The voxel-based morphometry (VBM) was used to calculate the gray matter volume. The results indicated that patients with MDD exhibited significantly lower dFC of the left rostral hippocampus (rHipp.L) with the right precentral gyrus, left superior temporal gyrus and left postcentral gyrus when compared to healthy controls at baseline. In MDD patients, the dFC of the rHipp.L with right precentral gyrus at baseline was correlated with both the rHipp.L volume and HAMD remission rate (RR%), and also mediated the effects of the rHipp.L volume on antidepressant performance. Our findings suggested that hippocampal functional activity in MDD might continue to act on its structure and further affect antidepressant performance, which provided a novel insight into the neurobiological mechanism of the development route of the therapeutic process for MDD.