The clinical applications of functional MR imaging.

Functional MR imaging, similar to positron-emission tomography, shows the regions in which cerebral blood flow changes as neurons are active in the performance of cognitive tasks. Blood flow increases (activation) exceed that needed to supply oxygen for the increased metabolic needs for the increased neuronal activity. Therefore, in regions with activation, the deoxyhemoglobin concentration in the capillary blood decreases below levels found in the brain where neurons are not active.