The degree of Granger causal modeling estimated influence for a brain region was reported to predict its blood oxygenation level-dependent (BOLD) activity level in the resting-state default mode network (DMN). Many brain disorders, such as Alzheimer's disease (AD), may alter the influence strength, activity levels, or both. Whether the relationship or prediction between these two will be affected under disease condition is unknown. In this study, the spontaneous brain activity, and inter-regional Granger causality connection were investigated over eight core DMN regions in AD patients in contrast to that in normal controls. Compared to normal control (NC), AD patients had both decreased BOLD activity level and Granger causal influence in medial prefrontal cortex and decreased activity level in inferior parietal cortex showed. However, the positive correlation between the BOLD activity level and the degree of the Granger causal modeling defined influence was found not altered by AD.
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