During the last two decades, new developments in functional MRI (magnetic resonance imaging) have made it possible to detect changes in the brain over time, as opposed to the "snapshot" produced by conventional MRI. Essentials of Functional MRI breaks down the technical challenges for physicians, researchers, and technologists who use functional MRI but may not be experts in the necessary math and physics. The author describes the theory and practical details of functional MRI (fMRI) methodology, including how to acquire and analyze images, and a wide range of examples demonstrate how fMRI has been used thus far. The author provides the essential information to study, understand, use, and teach the practical aspects of fMRI for those people who are most likely to extend its use into clinical practice.