On a foggy February morning in Oxford, England, I arrived at the John Radcliffe Hospital, a shiplike nineteen-seventies complex moored on a hill east of the city center, for the express purpose of being hurt. I had an appointment with a scientist named Irene Tracey, a brisk woman in her early fifties who directs Oxford University’s Nuffield Department of Clinical Neurosciences and has become known as the Queen of Pain. “We might have a problem with you being a ginger,” she warned when we met. Redheads typically perceive pain differently from those with other hair colors; many also flinch at the use of the G-word. “I’m sorry, a lovely auburn,” she quickly said, while a doctoral student used a ruler and a purple Sharpie to draw the outline of a one-inch square on my right shin.
Wearing thick rubber gloves, the student squeezed a dollop of pale-orange cream into the center of the square and delicately spread it to the edges, as if frosting a cake. The cream contained capsaicin, the chemical responsible for the burn of chili peppers. “We love capsaicin,” Tracey said. “It does two really nice things: it ramps up gradually to become quite intense, and it activates receptors in your skin that we know a lot about.” Thus anointed, I signed my disclaimer forms and was strapped into the scanning bed of a magnetic-resonance-imaging (MRI) machine.
The machine was a 7-Tesla MRI, of which there are fewer than a hundred in the world. The magnetic field it generates (teslas are a unit of magnetic strength) is more than four times as powerful as that of the average hospital MRI machine, resulting in images of much greater detail. As the cryogenic units responsible for cooling the machine’s superconducting magnet clicked on and off in a syncopated rhythm, the imaging technician warned me that, once he slid me inside, I might feel dizzy, see flashing lights, or experience a metallic taste in my mouth. “I always feel like I’m turning a corner,” Tracey said. She explained that the magnetic field would instantly pull the proton in each of the octillions of hydrogen atoms in my body into alignment. Then she vanished into a control room, where a bank of screens would allow her to watch my brain as it experienced pain.