Insula and amygdala resting-state functional connectivity differentiate bipolar from unipolar depression

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Differentiating depressive episodes in bipolar disorder (BD) and major depressive disorder (MDD) is clinically challenging.
• Emotional dysregulation is a core feature in both BD and MDD, but underlying neural mechanisms may differ.

Purpose of the Study:

• To compare resting-state functional connectivity (rsFC) in emotional regulation regions between similarly depressed patients with BD and MDD.
• To investigate if rsFC patterns can aid in distinguishing between these two depressive disorders.

Main Methods:

• Recruited 76 inpatients (36 BD, 40 MDD) and 40 healthy controls (HC).
• Utilized a seed-based approach focusing on the insula and amygdala to analyze rsFC.
• Performed insular and amygdalar parcellations and assessed diagnostic accuracy.

Main Results:

• Patients with BD showed lower rsFC between the left insula and left mid-dorsolateral prefrontal cortex, and between bilateral insula and right frontopolar prefrontal cortex (FPPFC), driven by dorsal anterior/posterior insula.
• Patients with MDD exhibited lower rsFC between the right amygdala and left anterior hippocampus, driven by centromedial/laterobasal amygdala.
• rsFC between the left posterior insula and right FPPFC achieved 78% accuracy in differentiating BD from MDD.

Conclusions:

• rsFC patterns in the amygdala and insula effectively distinguish between depressed BD and MDD patients.
• These findings suggest potentially different pathophysiological mechanisms underlying emotional dysfunction in bipolar versus unipolar depression.