Melanie Thernstrom lies motionless inside the large, noisy bore of a functional MRI scanner at Stanford University. She tries to ignore the machine's loud whirring as she trains her attention on a screen mounted inside the scanner, right in front of her eyes. An image of a flame bobs and flickers, shifting subtly in size. To her, the flame is a representation of the searing pain in her neck and shoulder, with its fluctuations reflecting the rise and fall of her discomfort. To the neuroscientists scrutinizing her through a window from the control room next door, the flame is a measure of the activity in a part of her brain.
As Thernstrom's pain increases, so does the amount of activity in part of this brain area, called the anterior cingulate cortex (ACC). This boomerang-shaped region, located in the frontal lobes, straddles the brain's midline between the ears and the forehead. Thernstrom's task is to will the flame to shrink, thereby reducing the neuronal hubbub in that region and the sensation of pain. With software rapidly parsing the machine's data to update the image of her ACC, Thernstrom can peer inside her own mind. She can observe, fuzzily, her brain's inner workings almost in time with the conscious manifestation of her discomfort.