Fig. 1.

Key steps of the CVR modeling methods compared in this manuscript. Reference timeseries are generated via external recordings or the BOLD MRI data. P_ETCO₂ and RVT timeseries are convolved with canonical response functions. For all methods, modeling is repeated for shifted variations of each reference time signal. On a voxelwise basis, the shift that optimizes the full model R² is selected. Maps of amplitude and delay are then generated using these parameters. P_ETCO₂ = partial pressure of end-tidal CO₂, RVT = respiration volume per time, BOLD = blood oxygenation level dependent, GM = gray matter, HRF = hemodynamic response function, RRF = respiration response function.