Elimination of visually evoked BOLD responses during carbogen inhalation: Implications for calibrated MRI

► Almost complete elimination of the visual BOLD response during carbogen-10 breathing. ► Venous saturation can be driven to very high levels during carbogen inhalation. ► Lower bound on M of 7.5% BOLD signal change. ► Preserved perfusion response to visual stimulus despite elimination of BOLD contrast. ► Estimated M value of 9.5% using a hybrid BOLD calibration model.