When American psychiatrist Mark S. George stepped into the elevator of a London hospital in 1990, he had no idea the short ride would transform his research career. A fellow passenger was having a giggling fit for no apparent reason. When George inquired about the outburst of merriment, the man replied that a doctor had held a magnetic coil against his head and that it had made his thumb twitch uncontrollably.
Even though the tale sounded a bit like quackery, George was curious. He contacted the doctor, who said he had stimulated the man's motor cortex, located at the top of the head, in hopes of seeing whether it would spark a signal to any muscles. The doctor had learned about what researcher Anthony T. Barker of the University of Sheffield in England did in the mid-1980s: Barker transmitted 4,000 amperes of current through a copper coil to create a strong, tight magnetic field, then held his homemade device against his own head. His thumb suddenly jerked up involuntarily. The magnetic field had obviously been strong enough to deliver a stimulus to the brain through the skull--transcranially.