Food For Thought

Over the past 10 years the field of cognitive neuroscience has emerged as a very important growth area in neuroscience. Cognitive neuroscience combines the experimental strategies of cognitive psychology with various techniques to actually examine how brain function supports mental activities. At the forefront of this research in normal humans are the new techniques of functional brain imaging: positron emission tomography (PET) and magnetic resonance imaging (MRI). The signals used by PET and functional MRI, or fMRI as it is now called, are based on the fact that changes in the cellular activity of the brain of normal, awake humans and laboratory animals are accompanied almost invariably by changes in local blood flow. This robust, empirical relationship has fascinated scientists for well over 100 years, but its cellular basis remains largely unexplained despite considerable research. Also, the accompanying metabolic changes do not appear to follow exactly the time-honored notion of a close coupling between blood flow and the oxidative metabolism of glucose.'.* On the occasion of this celebration of the career of Fred Plum, it seems especially appropriate to review both the history and the current status of the relationship between blood flow and brain function in the context of functional brain imaging. Over many years Plum and his colleagues have contributed substantially to our understanding of brain circulation and metabolism in both health and disease. Many of his students, including me, have worked to carry on that tradition in our own research.