Analysis of Dynamic Network Reconfiguration in Adults with Attention-Deficit/Hyperactivity Disorder Based Multilayer Network.

Attention-deficit/hyperactivity disorder (ADHD) has been reported exist abnormal topology structure in the brain network. However, these studies often treated the brain as a static monolithic structure, and dynamic characteristics were ignored. Here, we investigated how the dynamic network reconfiguration in ADHD patients differs from that in healthy people. Specifically, we acquired resting-state functional magnetic resonance imaging data from a public dataset including 40 ADHD patients and 50 healthy people. A novel model of a "time-varying multilayer network" and metrics of recruitment and integration were applied to describe group differences. The results showed that the integration scores of ADHD patients were significantly lower than those of controls at every level. The recruitment scores were lower than healthy people except for the whole-brain level. It is worth noting that the subcortical network and the thalamus in ADHD patients exhibited reduced alliance preference both within and between functional networks. In addition, we also found that recruitment and integration coefficients showed a significant correlation with symptom severity in some regions. Our results demonstrate that the capability to communicate within or between some functional networks is impaired in ADHD patients. These evidences provide a new opportunity for studying the characteristics of ADHD brain networks.

Deficit of Cross-Frequency Integration in Mild Cognitive Impairment and Alzheimer's Disease: A Multilayer Network Approach.

BACKGROUND: Studies at specific frequencies have shown abnormalities in brain functional networks among mild cognitive impairment (MCI) and Alzheimer's disease (AD) patients. Previous studies have failed to take into account the possibility that optimal cognitive integration requires interactions between different frequency bands. PURPOSE: To study whether there is abnormal cross-frequency integration in patients' brains during disease progression. STUDY TYPE: Retrospective. POPULATION: Forty-six normal control (NC), 85 patients with MCI, and 31 patients with AD. FIELD STRENGTH/SEQUENCE: 3T. ASSESSMENT: Multilayer network models were constructed for NC, MCI, and AD, and multilayer participation coefficient (MPC) was used to study the changes of the interlayer relationship in the course of disease development. In addition, MPC and an overlapping degree were combined to classify nodes in the network, and the role of key nodes in the interlayer interaction was mainly observed. Finally, the correlation between multilayer network measures and cognitive function was investigated. STATISTICAL TESTS: Pearson chi-squared two-tailed test, one-way analysis of variance (ANOVA), nonparametric Spearman correlation coefficient r, and the false discovery rate. RESULTS: The MPC of the network decreased significantly in MCI (P < 0.05) and AD (P < 0.05). The number of intralayer nodes increased significantly (MCI [P < 0.05], AD [P < 0.05]) and the number of interlayer nodes decreased significantly. Centrality loss between frequencies of a large number of hub nodes, among which the damaged hub nodes included the left hippocampus, left precuneus, right precuneus, left posterior cingulate gyrus, left precentral gyrus, right precentral gyrus, left medial superior frontal gyrus, and right postcentral gyrus. MPC was significantly associated with memory impairment in patients (AD [Spearman's r = 0.526, P < 0.05], MCI [Spearman's r = 0.229, P < 0.05]), and these related regions included damaged hub nodes in patients. DATA CONCLUSION: In the multilayer networks of patients, there was an obvious deficit in cross-frequency integration and the hub nodes were preferentially damaged. Moreover, these vulnerable hubs are associated with patients' cognitive scores. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 3.

Abnormal Dynamic Community Structure of Patients with Attention-Deficit/Hyperactivity Disorder in the Resting State.

OBJECTIVE: Some static network studies have suggested that the community structure in the brains of ADHD patients is altered. However, ADHD is now increasingly regarded as a disorder of neural dynamics, but the dynamic reconstruction of brain communities in ADHD patients is far from being understood. METHOD: Forty-two ADHD patients and fifty healthy controls participated in this study. We constructed a multilayer network model and calculated several metrics for quantifying community reconstruction at different levels. Results: Regardless of the level of research, the flexibility and cohesion of the ADHD patients were significantly higher than those of controls. In addition, the frontal lobe of ADHD patients presented a phenomenon of increasing peripheral areas and decreasing core areas. CONCLUSION: Our results indicate that ADHD patients do have abnormalities in dynamic community structure. These evidences provide a new perspective that advances the present understanding of the dynamic organizational principles of communities in ADHD.