Decreased insular connectivity in drug-naive major depressive disorder at rest

The insula has extensive links to the fronto-limbic circuit and associated regions, which is involved in the neurobiology of major depressive disorder (MDD). However, few studies are designed to examine the insular connectivity in MDD. This study was performed to examine the insular connectivity in drug-naive MDD directly by using the insular cortices as seeds.

Functional magnetic resonance imaging data were obtained from 44 drug-naive MDD patients and 44 healthy controls at rest. The functional connectivity (FC) method was used to analyze the images.

Significantly decreased FCs were found between the right insula and the left middle frontal gyrus (MFG, orbital part), left superior temporal gyrus (STG), right putamen, and right middle occipital gyrus (MOG), and between the left insula and the left superior temporal pole and right MOG in the patients compared with the controls. There were significantly negative correlations between the z values of the left insula-left superior temporal pole connectivity and the current episode duration (r=-0.332, p=0.028), between the z values of the right insula-left STG connectivity and the episode number (r=-0.343, p=0.023), and between the z values of the right insula-left MFG (orbital part) connectivity and the Automatic Thoughts Questionnaire scores (r=-0.359, p=0.017) in the patients.

The findings reveal that depressed patients have decreased insular connectivity with the fronto-limbic circuit, hate circuit, and visual regions, and suggest that the insula may act as an integration center of emotional processing which is disrupted in the depressed patients.