The hierarchical modular organization of functional networks in the brain is crucial for supporting diverse cognitive functions. Functional disorders in the brain are associated with an abnormal hierarchical modular organization. The default mode network (DMN) is a complex dynamic network that is linked to specialized cognitive functions and clinically relevant information. In this study, we hypothesize that hierarchical functional segregation and integration of the DMN within attention-deficit/hyperactivity disorder (ADHD) is abnormal.
(a) The DMN system is divided into three levels. The 1st level contains all the DMN regions. The 2nd level consists of two subnetworks within each hemisphere of the DMN, i.e., the left DMN (lDMN) and the right DMN (rDMN). Each hemisphere of the DMN is divided into two subnetworks in the 3rd level, i.e., the right anterior DMN (raDMN), the right posterior DMN (rpDMN), the left anterior DMN (laDMN) and the left posterior DMN (lpDMN). (b) The ROI number of each subnetwork in each DMN level. The 1st level of the DMN includes 28 ROIs, and the rDMN and lDMN each contain 14 ROIs. At the highest level, the laDMN and raDMN each consist of 6 ROIs, and the number of ROIs in lpDMN and rpDMN are 8 respectively.
