The effect of global cerebral vasodilation on focal activation hemodynamics.

In view of the potential of global resting blood flow level to confound the interpretation of blood oxygenation level-dependent (BOLD) fMRI studies, we investigated the effect of pronounced elevation in baseline cerebral blood flow (CBF) on BOLD and CBF responses to functional activation. Twelve healthy volunteers performed bilateral finger apposition while attending to a radial yellow/blue checkerboard. Three levels of global CBF increase were achieved by inhaling 5, 7.