An aberrant hippocampal subregional network, rather than structure, characterizes major depressive disorder

Area of Science:

• Neuroscience
• Psychiatry
• Neuroimaging

Background:

• Major depressive disorder (MDD) pathogenesis involves the hippocampus.
• Specific structural and functional abnormalities in hippocampal subregions in MDD are not well understood.

Purpose of the Study:

• To investigate hippocampal subregion-specific structural and functional abnormalities in patients with MDD.
• To correlate these abnormalities with depression severity.

Main Methods:

• Acquired multimodal magnetic resonance imaging (MRI) from 140 MDD patients and 44 healthy controls (HCs).
• Quantified hippocampal subregional volumes and fractional anisotropy (FA).
• Established hippocampal subregional networks using seed-based functional connectivity (FC) analysis and correlated metrics with depression severity.

Main Results:

• No significant differences in hippocampal subregional volumes or FA metrics were found between MDD patients and HCs.
• MDD group showed weaker connectivity in right hippocampal subregional networks with the temporal cortex and basal ganglia.
• Increased connectivity of the right subiculum to the bilateral lingual gyrus was observed, with specific FCs negatively correlated with depression severity.

Conclusions:

• Hippocampal subregional functional connectivity, not structure, is altered in MDD.
• Findings identify specific hippocampal subregional functional abnormalities contributing to the neurobiology of depression.