A MODEL FOR THE COUPLING BETWEEN CEREBRAL BLOOD-FLOW AND OXYGEN-METABOLISM DURING NEURAL STIMULATION

A general mathematical model for the delivery of O-2 to the brain is p resented, based on the assumptions that all of the brain capillaries a re perfused at rest and that all of the oxygen extracted from the capi llaries is metabolized. The model predicts that disproportionately lar ge changes in blood flow are required in order to support small change s in the O-2 metabolic rate. Interpreted in terms of this model, previ ous positron emission tomography (PET) studies of the human brain duri ng neural stimulation demonstrating that cerebral blood flow (CBF) inc reases much more than the oxygen metabolic rate are consistent with ti ght coupling of flow and oxidative metabolism. The model provides a ba sis for the quantitative interpretation of functional magnetic resonan ce imaging (fMRI) studies in terms of changes in local CBF.