In the classical picture of brain function, electrical impulses are initiated in sensory organs and spread rapidly down axons, jumping synaptic clefts by neurochemical transmission. Patterns of electrical activity generated in this way integrate information throughout the brain and result in coordinated motor output. Even as this picture of the central role of electrical transmission was emerging in the mid-20th century, the more speculative neuroscientists reasoned that there must be more to it. In order to store information and adapt to a changing environment, neurons must be able to alter their own properties or those of their neighbors, in highly controlled ways, sometimes permanently.