Deep brain stimulation modulates directional limbic connectivity in major depressive disorder

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Deep brain stimulation (DBS) is explored for treatment-resistant major depressive disorder (MDD).
• The precise mechanisms underlying DBS's antidepressive effects remain unclear.
• This study investigates DBS's impact on the amygdala-centric limbic network.

Purpose of the Study:

• To determine if ventral anterior limb of the internal capsule stimulation modulates the amygdala-based limbic network in MDD patients.
• To explore functional and effective connectivity changes associated with DBS treatment.

Main Methods:

• Resting-state functional magnetic resonance imaging (fMRI) was used in nine MDD patients before and after 1 year of DBS.
• fMRI scans were also conducted during a double-blind, cross-over phase with active and sham stimulation.
• Functional connectivity (FC) analysis and dynamic causal modeling (DCM) were employed to analyze imaging data.

Main Results:

• One year of DBS increased left amygdala functional connectivity with the precentral cortex and left insula.
• DBS decreased nucleus accumbens connectivity with the ventromedial prefrontal cortex.
• Dynamic causal modeling revealed amygdala-centric network changes from pre-surgery to 1-year follow-up, with insula-centric changes during the active vs. sham stimulation phase.

Conclusions:

• Ventral anterior limb of the internal capsule DBS induces significant network rebalancing in the limbic system.
• These changes involve emotion, reward, and interoceptive processing pathways.
• The findings provide insights into the neurobiological underpinnings of DBS for major depressive disorder.