Consistent pivotal role of posterior cingulate cortex in the default mode network revealed by partial correlation analysis

Resting-state functional MRI (fMRI) studies have suggested the posterior cingulate cortex (PCC) plays a pivotal role in the default mode network (DMN), a set of co-activated brain regions characterizing the resting-state brain. Concerning this finding we propose the following questions in this study: Does PCC consistently play the equally crucial role in the DMN across different subjects, such as healthy young and healthy old subjects? Whether the fMRI scan environments or parameters would affect the results? To address these questions, we collected resting-state fMRI data on four groups of subjects: two healthy young groups scanned under 3-T and 1.5-T MRI systems respectively, and two healthy elderly groups both scanned under 3-T MRI system but with different scan parameters. Then group independent component analysis was used to isolate the DMN, and partial correlation analysis was employed to reveal the direct interactions between brain regions from the DMN. Finally, we measured the connectivity between brain regions based on the number of significantly interacted links to every region within this network. We found that PCC was the brain region consistently having the largest number of directly interacted regions in the four groups, suggesting the pivotal role of PCC in the DMN was stable and consistent across healthy subjects. The results also suggested the function of PCC would be more critical in healthy elderly subjects compared with healthy young subjects. And the factors of scan environments and parameters did not show any obvious impact on the above conclusions in this investigation.