Increased involvement of the parahippocampal gyri in a sad mood predicts future depressive symptoms

Abstract

Behavioral studies suggest a relationship between autobiographical memory, rumination and depression. The objective of this study was to determine whether remitted depressed patients show alterations in connectivity of the posterior cingulate cortex (PCC, a node in the default mode network) with the parahippocampal gyri (PHG, a region associated with autobiographical memory) while intensively recalling negative memories and whether this is related to daily life symptoms and to the further course of depression. Sad mood was induced with keywords of personal negative life events in participants with remitted depression (n = 29) and matched healthy controls (n = 29) during functional magnetic resonance imaging. Additionally, daily life assessments of mood and rumination and a 6-month follow-up were conducted. Remitted depressed participants showed greater connectivity than healthy controls of the PCC with the PHG, which was even stronger in patients with more previous episodes. Furthermore, patients with increased PCC-PHG connectivity showed a sadder mood and more rumination in daily life and a worsening of rumination and depression scores during follow-up. A relationship of negative autobiographical memory processing, rumination, sad mood and depression on a neural level seems likely. The identified increased connectivity probably indicates a 'scar' of recurrent depression and may represent a prognostic factor for future depression.

Keywords: autobiographical memory; default mode network; depression; parahippocampal gyri; rumination.