The brain is the medium of the mind, the physical substance that gathers, stores, recalls, and generates perceptions, information, ideas, and emotions. Despite its central role in understanding our environment, how the brain functions had long remained a mystery. Over the last twenty years, however, new tools have allowed researchers to peer inside the brain while it works. Most notably, functional magnetic resonance imaging (fMRI) tied to computational techniques has provided a non-invasive technique to monitor brain activity down in real time to the resolution of less than a cubic millimeter.  Older technologies...