BY MITCH LESLIE

Hypnosis can change how we see the world, a new Stanford study has revealed. By using PET scans to monitor neural activity, researchers demonstrated that the brain processes visual input differently under hypnosis ­ allowing subjects to “see” color when they are actually staring at a black-and-white image. By bolstering the idea that hypnosis transforms perception, the study supports the use of the technique to improve athletic and intellectual performance and even to “think away” pain.

The question of how to interpret hypnosis divides psychiatrists into two camps, said David Spiegel, MD, professor of psychiatry and behavioral sciences and senior author on the study. He and many other psychiatrists regard hypnosis as a genuine mental state, in which our perception of reality changes and our mind ­ like a telephoto lens ­ zooms in on a subject.

But skeptics argue that hypnosis is a form of trickery. Far from inducing a focused mental state, it merely makes people extremely agreeable ­ and then they obligingly report seeing, hearing or feeling whatever the hypnotist wants.

The disagreement persists because testing these theories requires a way to differentiate what people perceive from what they claim to perceive. To identify what the brain really “sees” during hypnosis, Spiegel and colleagues from Harvard, Massachusetts General Hospital and Memorial Sloan-Kettering Cancer Center in New York City used a PET (for positron emission tomography) scanner to monitor activity in the brain’s visual areas. A PET scanner gauges blood flow to different parts of the brain to detect which regions are active.

Hypnotized and unhypnotized subjects observed a colored patchwork of squares or an identical pattern in which the squares were shades of gray. The researchers suggested that the subjects visualize each image as either color or black-and white.

All the while, the PET scanner was measuring how hard the cells in two visual areas were working. The immediate decoding of nerve impulses from the eyes takes place in the occipital lobe at the back of the brain, Spiegel said. But to interpret this raw data, the brain needs to summon up memories and make comparisons ­ an activity that occurs farther forward, in the temporal lobe.

As the researchers reported in the August issue of the American Journal of Psychiatry, under hypnosis the brain sees what it’s told to see. When a hypnotized subject was told to visualize the image in color, the color-processing areas in the brain lit up ­ regardless of whether the actual image was color or black-and-white. And when the instructions were to visualize the image in grays, the brain always responded as if scanning an old black-and-white photo.

Without hypnosis, the results were much different. The left side of the brain always remained true to the image. The color-processing areas only activated when the colored pattern was shown, for example. However, the right side of the brain responded as if hypnotized, seeing what the hypnotist suggested instead of the true colors.

Spiegel thinks the characteristics of the study volunteers may explain this difference between right and left hemispheres of the brain. All eight were “highly hypnotizable” adults. Most of us can be hypnotized, Spiegel said, but only about 10 percent of us have the capacity for intense concentration and qualify as highly hypnotizable. As the study volunteers focused on the image and tried to mentally re-paint it, they may have slipped into a near-hypnotic state, during which they responded to the hypnotist’s suggestions.

“This study lends considerable weight to the idea that hypnosis is a real neurological phenomenon,” Spiegel said. “But our goal is not just to verify a hypothesis. With hypnosis, we can help people modulate perceptions in ways that are therapeutically helpful.”

Reducing pain through hypnosis is one of the applications Spiegel is exploring. In a study published last February in the Lancet, he and his colleagues reported that self-hypnosis could ease pain for patients receiving radiation treatment. Spiegel and his colleagues found that the patients who learned self-hypnosis not only reported feeling less pain, they used half the amount of pain medication. “They are not just suffering in silence ­ they are able to change their perception of pain,” Spiegel said.

Hypnosis may also help boost our performance in a number of activities, from test-taking to sports. “Hypnosis can be very helpful in allowing you to focus on what you want to focus on,” Spiegel said. After playing well, athletes often claim to have been “in the zone” ­ it’s become one of sports’ most overused cliches. Yet there is some truth in the cliche, Spiegel said. Top-flight athletes may urge themselves into a state of heightened focus that is close to a hypnotic state.

Spiegel recalls that one of his students, a wide receiver on the Stanford football team, described how, when playing well, he could exclude everything from his mind except two things: the ball and the defender covering him. That’s a formidable act of concentration, considering that “he’s running around on the field with 20 other large guys,” Spiegel said.

Spiegel’s collaborators on the study were Stephen Kosslyn, PhD; William Thompson; Maria Costantini-Ferrando, PhD; and Nathaniel Alpert, PhD.

A grant from the Mind/Body Research Network of the John D. and Catherine T. MacArthur Foundation supported the work. SR