The brain, wondrous as it is, poses a special challenge for scientists. Mental disorders play out in a 3-lb. universe that is largely inaccessible without drastic--and extremely risky--surgery. At least it was until the 1970s, when the first crude pictures of the living brain were taken. Today researchers can peer into that universe with a variety of scanning technologies that capture the brain in action and send back beautifully detailed images that are the next best thing to being there.
The best results come from combining two or more scanning methods. Some capture the size and shape of brain structures; others freeze-frame the ever shifting activity of nerve cells as they fire and subside. With this information, doctors are beginning to understand--at the level of the neuron--how mental illnesses occur. "Brain imaging," says Dr. Nancy Andreasen, a leading schizophrenia researcher at the University of Iowa and the MIND Institute in Albuquerque, N.M., "has changed the face of psychiatry."
Schizophrenia is where much of the pioneering work in this field has occurred, and the images on the following pages trace the remarkable journey that scientists are taking as they search for the roots of this disorder and perhaps someday a cure.
1970s Computed Tomography (CT)
CT scans represent a major advance over the simple X ray, which did not allow doctors to visualize brain tissue at all. Instead of a flat, two-dimensional X-ray picture, CT scanners produce a series of successive images. Taken as the patient, lying down, moves through a scanning ring, these "slices" can be combined to create the illusion of depth. The resulting pictures of bone and soft tissue can help doctors distinguish between patients with a psychiatric disorder and those with head trauma (which can trigger similar symptoms). CTs have been particularly useful in identifying schizophrenia patients. In the 1970s researchers uncovered the first distinguishing abnormality in these patients' brains: the ventricles (fluid-filled open spaces), circled in yellow, are significantly larger in those with the disease, left, than in normal subjects, far left. This provided the first clue that schizophrenics may have less brain tissue affecting cognitive functions such as attention and memory.
1980s Magnetic Resonance Imaging (MRI)
This technology takes advantage of the body's natural magnetic field, measuring changes in the field's energy as patients are exposed to various radiofrequencies. Unlike CT views, MRIs can be rendered in full 3-D because MRI machines can slice along three or more planes, not just one. A computer can then compile the information to generate a sort of relief map of the brain, left, depicting even the smallest brain structures (for example, the brain's center for emotion, the amygdala, in yellow, is deeply buried but visible). Using MRIs, scientists have learned that the brains of schizophrenics, above right, are smaller than those of people without the disease, above left, and that they have smaller frontal lobes, the part of the brain responsible for planning, decision making, higher learning and emotions.
1980s Positron-Emission Tomography (PET)