Figure 2.

CO ₂ time evolution vs. BOLD signal in two illustrative voxels. For each processing method, the shifted CO ₂ timeline (green) is plotted against the BOLD signal time series of two random voxels (one in the white matter: red, and one in the gray matter: blue) together with the linear fitting of the BOLD vs. CO2 scatter plot and the respective CVR map. In figure 2.1, the CO ₂ time series correspond to CO ₂ time course without time shift. figure 2.2 shows a single global CO ₂ time shift for the whole‐brain (Delay_global) and figure 2.3 correlation CO ₂ time shift (CO ₂‐BOLD) on a voxel‐wise basis after maximum correlation (Delay_maxcorr); figure 2.4 shows the respective duration of the DTP and the DTB for both voxels with the dynamic (CVR _corr) and static (CVR _stat) CVR maps. The fitting of figure 2.4 is based on CVR _stat, scatter plot which shows clearly removal of the transition phases between the two static states. The shifts of the CO ₂ timeline are: Delay_global: red: 7 TRs, blue: 7 TRs; Delay_maxcorr: red: 20 TRs, blue: 5 TR; Delay_corr: red 9 TR, blue: 1 TR. CO ₂, Carbon dioxide; BOLD, Blood‐oxygen‐level‐dependent; CVR, cerebrovascular reactivity; DTP, Delay to Plateau; DTB, Delay to Baseline