Reconstruction of functional brain network in Alzheimer's disease via cross-frequency phase synchronization

Changes in functional brain connectivity have been associated with the progression of Alzheimer's disease (AD). However, the investigation of functional connectivity by electroencephalographic (EEG) is usually limited to within certain frequency bands. In this study, we reconstruct the functional brain network of AD patients with both within and between band connectivity using resting-state EEG. Through the cross-frequency phase synchronization technique, we find that the cross-frequency connectivity is different between groups and among brain regions. Especially, the connectivity strength is significantly declined between delta and other bands for patients. In addition to these differences, a negative correlation can be found between within and cross frequency synchronization in AD. We further calculate the graph metrics of functional brain networks to investigate the alteration of network dynamics in AD. Compared to the controls, the patients exhibit elevated small world properties in the cross-frequency networks, indicating an impaired balance between within and cross frequency interaction. These findings suggest that they may provide new insights into the underlying brain dynamics in AD.