Mapping brain terrain.

The brain has revealed many of its secrets during the decade dedicated to its honor. Many of the exquisite techniques used in quite ingenious ways to uncover the workings of the brain involve microanalysis of the chemistry and biophysics of the brain’s complex and varied cellular structure. But, most revelations that can be readily appreciated by a general audience come from the giant leaps made in brain imaging. In this field we can see the human brain in action. We can see the brain registering a sound, a sight, or a touch. We can capture the neural origins of the movement of a finger or toe or the complex movement involved in uttering a word. We can image a thought process. Skilled investigators are dissecting the inner workings of the mind, seeing behavior in the functioning brain in startling and compelling ways. Herein are described the tools that have revealed much. Investigators such as Marcus Raichle, Richard Frackowiak, and John Mazziotta have pioneered work that is inherently interesting and has a solid application in clinical settings for diagnosis and treatment. The new advances that allow imaging of the brain are driven by the biology of the brain and its control of its own blood flow, complex physical principles, and computer technology. These several advances of modern technology have enabled us to understand the structure and function of the mind. With the newest technologies we can actually see a thought formulate in the mind. Among these are magnetic encephalography, functional magnetic resonance imaging, and positron emission tomography. Most of these approaches have become rather well known to the world-at-large. Human brain imaging began in the early seventies with X-ray computed tomography (CT or CAT), which shows only coarse structure. The real underlying advance was the ability to generate, using computers, maps of the brain taken from signals being generated and recorded.