Abstract

Background: Hippocampal volume is reduced in Major Depressive Disorder (MDD), but the extent to which hippocampal function is altered in the context of MDD, particularly in young adults, is not well established. The hippocampus is important in recollection memory, a cognitive domain that is often impaired in depressed adults.

Objective: This pilot functional Magnetic Resonance Imaging (fMRI) study aimed to assess hippocampal activity during a verbal memory task in unmedicated young adults with MDD (18-24 years of age) relative to healthy age-matched Controls.

Method: Brain activity was measured in hippocampal regions during verbal encoding and retrieval, and compared between groups (N=11 in each group); exploratory whole-brain assessments were also carried out.

Results: Greater right hippocampal activity during verbal memory encoding (vs. retrieval) was apparent in Controls. Further, in the MDD group, left hippocampal activity during encoding (vs. retrieval) was positively related to depression symptom severity and number of previous depressive episodes.

Conclusion: This pilot study is a stepping stone in examining the effect of depression on hippocampal function in young adults.

Keywords: Depression, fMRI, hippocampus, memory, youth, MDD.