The dynamic characteristics of the anterior cingulate cortex in resting-state fMRI of patients with depression

Background: The anterior cingulate cortex (ACC) is part of the limbic system of the brain. It is a bridge between attentional and emotional processing, which is responsible for the integration of visceral, attentional, and affective information. Lesioning of the ACC, which produces striking changes, is used to treat major depression disorder (MDD). Moreover, the brain dynamically integrates and coordinates functions of its different subparts to realize its cognitive capability. Hence, the spatio-temporal community distribution of the ACC is necessary to completely understand MDD. Methods: First, community structure detection was used to reveal the community distribution of brain regions. Thereafter, the flexibility, i.e., the frequency of community assignment changes of the ACC in such a community, and the module allegiance matrix (MAM) between the ACC and other brain regions, were analyzed. Results: Our analysis demonstrated significant differences in the distribution of community assignment and flexibility of the ACC in MDD, compared to healthy controls (HC). The results also showed that the pairwise values of the MAMs between the ACC and the amygdala, insula, precuneus, and thalamus were significantly lower in patients with MDD compared to those in HC. Limitations: The data collected is subject to patient-specific noise because (1) the medication effect varies from patient to patient, and (2) with most fMRI studies, the thoughts of the participants during imaging are difficult to control. Conclusion: ACC exhibits abnormal flexibility in community structures in MDD. The pairwise abnormal entries in the MAM for the ACC with four other brain regions, i.e., amygdala, insula, precuneus, and thalamus, quantified the role played by the ACC in MDD.