FIG. 2.
PCA analysis performed on five different single fMRI runs. The three time-courses in each panel correspond to the GAS, the PC-based global effect estimator, and the average of the remaining specific resting-state fluctuations (after regressing out the PC-based estimator). (A) A typical run where the GAS correlated best with the 1st PC, with a highest correlation value obtained over the sample (r=0.99). (B) A typical run where the GAS correlated best with the 1st PC with the median correlation value over the sample (r=0.95). (C) A typical run in which the GAS correlated best with the 1st PC; however, the correlation was the minimal over the sample (r=0.72). (D) and (E) show the time-courses associated with the two atypical runs, where the GAS correlated best with the 2nd PC. fMRI, functional magnetic resonance imaging.