Postcards From The Brain

By Alice Park

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)

PET scans capture images of the brain in action. Patients receive an injection of a radioactive tracer that allows scientists to track how much blood is flowing through various regions of the brain and how much glucose is being broken down by the brain cells (both are good indications of how many neurons are firing). PET images have proved indispensable for schizophrenia researchers, showing them that the disease is not located in a single region of the brain but stems from a difficulty that distant regions have in communicating with one another. When schizophrenics are asked to remember words, for example, the areas of the brain responsible for attention and working memory, in red, far right, activate at a much lower level than in normal subjects, right.

1990s Functional Magnetic Resonance (fMR)

An advance over PET imaging, fMR also measures brain function but does not require radioactive tracers. Instead, this technique tracks brain activity by monitoring changes in how much oxygen the brain cells are consuming. That serves as an indicator of how much blood is flowing to various brain regions, which in turn shows how active the nerve cells are. Typically, fMR subjects are placed in an MRI machine and asked to perform a mental task such as remembering and repeating words presented to them. Schizophrenic patients reading and learning the words activate the same regions of the brain as normal subjects do, in yellow, right, top row, but with much less blood flow and therefore less nerve firing, right, bottom row.

2000s Magneto-encephalography (MEG)

Not satisfied with just capturing the brain at work, scientists have developed an exciting new technique that allows them to study the brain in real time. MEG directly measures nerve-cell firing by detecting changes in tiny magnetic signals produced by active brain neurons. It is ideal for tracing the order and pattern in which brain regions are activated when performing certain tasks. This series of images, above, depicts a normal subject presented with a list of new words. The neurons fire in a wave that progresses from the back of the brain, in yellow, top, where the visual region is located, to the frontal lobes. Researchers are using the same technique with schizophrenic patients to learn whether there is a different pattern to their nerve firings.

ABC For more on the latest technology that allows us to peer inside the brain, tune in to ABC World News Tonight with Peter Jennings. Tuesday, Jan. 14, 6:30 p.m. E.T.