Neuroscience has made considerable progress in figuring out how the brain works. We know much about the molecular-genetic and biochemical underpinnings of sensory and motor functions, and recent neuroimaging work has opened the door to investigating the neural underpinnings of higher-order cognitive functions, such as memory, attention, and even free will. In these types of investigations, researchers apply specific stimuli to induce neural activity in the brain and look for the function in question. However, there may be more to the brain and its neuronal states than the changes in activity w