Limbic-cortical Dysfunction In Patients With Major Depresion: An Event-related FMRI Study With The Negative Priming Task

Objective: Individuals with major depressive disorder (MDD) not only preferentially process negative stimuli, but also lack a bias for the preferential processing of positive stimuli. The present study aimed to examine neural correlates of inhibitory dysfunction in MDD individuals.Method: The study adopted event-related functional magnetic resonance imaging design. Twelve MDD participants and 12 never-depressed controls underwent scanning during performance of the negative affective priming (NAP) task using functional magnetic resonance imaging(fMRI). The task allowed comparison between neural response during negative priming (inhibition) and in the absence of negative priming (no inhibition) for happy and sad faces, respectively.Results: A less effective inhibition in MDD patients was specific for negative information. However, these behavioral effects were not paralleled by fMRI response difference. MDD participants were found to exhibit strong activation to both types of emotional stimuli in the right dorsal anterior cingulate(dCg), bilateral inferior frontal gyrus(IFG), left inferior parietal(inf Par)and insula cortex(IC), whereas the control group showed deactivation in the above brain regions. Further, an interaction between group and valence was seen in the left hippocampus and thalamus.Conclusions: The imaging findings suggest that impaired inhibition for affective information in MDD patients involves the failure of the coordinated interactions of a distributed network of limbic-cortical pathways, specifically, between the dorsal cortical and ventral limbic networks that regulate a variety of behaviors, including the interaction among mood, cognitive, somatic, and autonomic responses.