Graph theoretical analysis of EEG effective connectivity in vascular dementia patients during a visual oddball task

Objective: The study was dedicated to investigating the change in information processing in brain networks of vascular dementia (VaD) patients during the process of decision making. Methods: EEG was recorded from 18 VaD patients and 19 healthy controls when subjects were performing a visual oddball task. The whole task was divided into several stages by using global field power analysis. In the stage related to the decision-making process, graph theoretical analysis was applied to the binary directed network derived from EEG signals at nine electrodes in the frontal, central, and parietal regions in delta (0.5-3.5 Hz), theta (4-7 Hz), alpha(1) (8-10 Hz), alpha(2) (11-13 Hz), and beta (14-30 Hz) frequency bands based on directed transfer function. Results: A weakened outgoing information flow, a decrease in out-degree, and an increase in in-degree were found in the parietal region in VaD patients, compared to healthy controls. In VaD patients, the parietal region may also lose its hub status in brain networks. In addition, the clustering coefficient was significantly lower in VaD patients. Conclusions: Impairment might be present in the parietal region or its connections with other regions, and it may serve as one of the causes for cognitive decline in VaD patients. The brain networks of VaD patients were significantly altered toward random networks. Significance: The present study extended our understanding of VaD from the perspective of brain functional networks, and it provided possible interpretations for cognitive deficits in VaD patients. (C) 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.