The Effect of Global Cerebral Vasodilation on Focal Activation Hemodynamics
Stefanovic B, Warnking J, Rylander K, Pike B
We investigated the effect of pronounced CO2-induced elevation in baseline cerebral blood flow (CBF) on BOLD and CBF responses to functional activation. A strong attenuation of the BOLD response (by ~57% in motor cortex and ~55% in the visual cortex) and a slight decline in the CBF response (by ~14% in MC and 2% in VC) was observed at significantly elevated basal perfusion level. The findings call for independent quantification of resting CBF in BOLD fMRI studies that involve subjects and/or conditions with markedly elevated global perfusion.