Aberrant default-mode network-hippocampus connectivity after sad memory-recall in remitted-depression

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• Rumination and cognitive reactivity are heightened in remitted Major Depressive Disorder (MDD), potentially predicting relapse.
• Previous studies linked these factors to altered resting-state functional connectivity in the Default-Mode Network (DMN).
• Prior research in remitted MDD was confounded by antidepressant use, necessitating medication-free investigations.

Purpose of the Study:

• To investigate if increased DMN connectivity persists in medication-free, remitted MDD patients.
• To determine if sad mood induction differentially affects DMN connectivity in remitted MDD versus controls.
• To correlate DMN connectivity with cognitive reactivity and rumination as vulnerability markers for recurrence.

Main Methods:

• Recruited 62 remitted MDD patients (≥2 episodes, medication-free) and 41 controls.
• Administered neutral and sad mood inductions via autobiographical recall and music.
• Acquired resting-state fMRI scans (8-min) after each mood induction; analyzed DMN components using Independent Component Analysis.

Main Results:

• Controls showed increased posterior DMN-hippocampal connectivity after sad mood induction, unlike remitted MDD patients.
• Reduced posterior DMN-hippocampal connectivity in remitted MDD correlated with higher cognitive reactivity (r=-0.21, P=0.046).
• This reduced connectivity also correlated with higher rumination (r=-0.27, P=0.017) in remitted MDD patients.

Conclusions:

• Aberrant posterior DMN-hippocampal connectivity persists in medication-free remitted MDD.
• This altered connectivity, particularly after sad mood recall, is associated with cognitive reactivity and rumination.
• These findings suggest a persistent neural vulnerability in remitted MDD, potentially predicting future depressive episodes.