Cerebral Blood Flow Mapping the Brain

Cerebral blood flow reflects the neural activity of the brain. This chapter discusses the mechanism by which neural activity is translated into cerebral blood flow. Initially, it was naively believed that cerebral blood flow increased to support the brain during activity from a feedback theory point of view. However, after many experiments and much discussion of cerebral circulation physiology, it was eventually realized that feedback theory does not fit to the real situation. A feed forward mechanism based on vascular mediators was shown to be more likely. In addition, the discovery of BOLD contrast with MRI opened a new platform for neuroscience research and there was a rapid increase in the neuroscientist population. Using BOLD contrast has widened the field of brain function mapping. The research paradigm has changed from finding activity foci in the brain with PET, to mapping networks of regions that are somehow connected during brain activity even during the resting condition. This chapter will discuss the physiological mechanism by which cerebral blood flow reflects brain activity and explores the mystery of why cerebral blood flow maps brain function in so much detail.