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.

Emotion-Dependent Functional Connectivity of the Default Mode Network in Adolescent Depression

“…Supporting this notion is our finding that stronger PCC connectivity during emotional processing was significantly associated with an earlier age of depression onset (Figure S2C). Connectivity between the PCC and parahippocampal cortex during recollection of negative life events has also been shown to increase with the number of depressive episodes, as well as the frequency and subsequent prediction of sad mood in daily life (128). Individuals with an increased genetic risk for developing depression also exhibit altered PCC connectivity with the amygdala during emotional regulation—but not during resting-state (129).…”

Cortical Thickness in Individuals at High Familial Risk of Mood Disorders as They Develop Major Depressive Disorder

“…Our research group has recently shown that individuals with a high risk of mood disorders who are homozygous for risk haplotype of the DGKH gene show relatively greater brain activation of the right parahippocampus during a verbal fluency task as compared with low-risk haplotype subjects, with the reverse pattern being observed for healthy control subjects (53). Furthermore, it has been shown that remitted depressed patients maintain an increased connectivity of the posterior cingulate cortex with the parahippocampal gyrus and that greater connectivity appears to represent a prognostic factor for future depressive episodes (54).…”

Neural substrates of rumination tendency in non-depressed individuals

“…The medial temporal lobe in general, and more particularly the parahippocampal gyrus, has also been postulated to mediate self-referential associations in depression (Bar, 2009). Increased connectivity between this region and the posterior cingulate cortex could mediate the relationship between autobiographical memories and rumination and represent a neural substrate of vulnerability to depressive episodes (Zamoscik, Huffziger, Ebner-Priemer, Kuehner, & Kirsch, 2014). A link between rumination tendency and hippocampus activation has also recently been suggested (Mandell et al, 2014).…”