Alterations in resting-state ALFF and functional connectivity linked to implicit and explicit suicidal ideations in...

This study aimed to explore the neurobiology of implicit and explicit suicidal ideation (SI) in depression. Seventy-four patients with major depressive disorder (MDD) along with 74 age- and gender- matched healthy controls were enrolled. The Death/Suicide implicit association test (D/S-IAT), the explicit Beck Scale for Suicidal Ideation (BSSI), and Resting-state functional magnetic resonance imaging (rs-fMRI) scanning were administered. The amplitude of low-frequency fluctuations (ALFF) was calculated and compared between groups to identify brain regions showing spontaneous neural activity related to implicit and explicit SI, and then seed-based functional connectivity (FC) was performed among these regions to reconstruct brain networks related to SI. Behavioral analysis demonstrated higher implicit SI (D values from D/S-IAT) in MDD patients, when compared to HCs，which was also significantly correlated with explicit SI (BSSI scores). Whole brain regression analysis indicated abnormal ALFF in the right postcentral gyrus associated with implicit SI, while ALFF alterations in the left insula, postcentral gyrus, and right middle temporal gyrus (MTG) was associated with explicit SI in MDD. Furthermore, FC analysis revealed increased connectivity between the right postcentral gyrus with the right SFG, MFG, MTG, SPG, insula, and amygdala for implicit SI. Conversely, higher FC between the left insula ROI and left SFG, as well as between the right MTG and left MFG and IPL for explicit SI. These findings suggesting partly overlapped but largely distinct neural basis of the implicit and explicit SI in the brain.