Aberrant topological organization of the default mode network in temporal lobe epilepsy revealed by graph-theoretical analysis

Numerous neuroimaging studies have reported aberrant functional activities of the default mode network (DMN) in temporal lobe epilepsy (TLE). However, the alteration on topological organization within the DMN has not been clearly illuminated. In this study, we aimed to investigate the topological abnormalities within the DMN from a larger-scale perspective. Twenty three patients with TLE and 23 age, gender, and education matched healthy controls (HCs) were recruited in this study. All participants underwent a resting-state functional magnetic resonance imaging (rs-fMRI) scanning and completed the Attention Network Test (ANT) for executive function assessment. Specific subregions in the DMN were extracted for network construction according to the automated anatomical labelling atlas. Network properties, including global properties, nodal properties and edge analyses, were assessed using graph theory. Correlation analyses were performed between significantly different topological properties and clinical factors in patients. The ANT tests showed that executive function was impaired in the patients with TLE compared with the HCs. Furthermore, the TLE group showed decreased nodal strength in the left medial orbital superior frontal gyrus and increased nodal strength in the right inferior parietal gyrus in the DMN. Significantly increased functional connectivities between subregions in the DMN were primarily located in the bilateral superior frontal gyrus, inferior parietal gyrus, precuneus, and posterior cingulate gyrus. Moreover, the degree centrality of the right inferior parietal gyms was positively correlated with disease duration. In conclusion, this study indicated that there existed a disrupted topological reorganization within the DMN in patients with TLE, which may further contribute to executive deficits and, to some extent, play a compensatory role.