Figure 5
Scheme of hypothetical blood-flow regulation during brain activation. Relationship between ΔrCBV and ΔrCBF in the activated area is shown by black line. Relationship between ΔO2 inflow and ΔrCBF in the activated area is shown by red line. During moderate neuronal activation, rCBF, rCBV and O2 inflow increase in the activated area (functional hyperemia). Above a certain level of neuronal activation, dissociation of increase in rCBF and rCBV takes place to prevent excess O2 inflow into the focally activated area (Flow-Mass regulation). Normal regulation of rCBF and rCBV is probably achieved by the action of both regulations (i.e., functional hyperemia and Flow-Mass regulation). Further, we hypothesize that when Flow-Mass regulation is disrupted (e.g., arteriosclerosis), rCBF, rCBV, and O2 inflow may increase to undesirable levels in the activated area, leading to the production of harmful reactive oxygen species resulting in accumulation of neuronal damage.