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New twists for phantom limbs

An experiment explores the connections between brain and body

By
12:00am, November 25, 2009

“Phantom” pain is like a ghost in the body — but it’s anything but imaginary. People who have had an arm or leg amputated can often still feel sensations of the missing limb, even though it’s no longer there. These sensations can be painful, and scientists are always looking for new ways to help relieve this phantom pain for amputees. Treatment often involves using mirrors to visually trick the person’s brain. The thinking is that, if a person can “see” his own body in a new way, his brain may stop sending pain messages.

In a new study, a team of neuroscientists have made another surprising discovery about amputees: They can be taught to mentally move their missing limbs in ways that are impossible in the real, physical world. It’s impossible for a person to bend his wrist down and then twist his hand around in a full circle.

Seven people who had had their arms amputated above the elbow participated in the experiment. After extensive mental training, four of the seven were able to feel the sensation of this impossible act, and describe it in detail.

“It is very surprising that anybody — amputees or not — can learn impossible movements just by thinking about it,” Henrik Ehrsson of the Karolinska Institutet in Stockholm, told Science News. Ehrsson is a neuroscientist, which is a scientist who studies the brain and nervous system.

Although the study itself is interesting, it may be able to help people with other kinds of mental disorders. A person with anorexia nervosa, for example, loses her appetite and/or stops eating, sometimes with fatal results. People with anorexia are usually believed to have a distorted self-image and often see themselves in an extremely negative way. But people suffering from this condition may benefit from this new research, Lorimer Moseley of the Prince of Wales Medical Research Institute in Randwick, Australia, told to Science News. Just as amputees imagined their phantom limbs could move in impossible ways, a person with anorexia may be able to change self-image by concentrating on a change to the body.

V.S. Ramachandran is a neuroscientist and the director of the Center for Brain and Cognition at the University of California, San Diego. In his research, Ramachandran has shown that phantom pain can be reduced with the help of a mirror. The mirror is placed so that when the amputee looks in the mirror, it looks like he has both hands. As he looks at the reflection, he clenches and unclenches his one hand while—and it appears as though both hands and are clenching and unclenching. At the same time, he mentally clenches and unclenches his phantom hand. When he sees both hands unclenching, he feels pain lessen.

Ramachandran says his mirror therapy, as well as the new research, show that much is left to learn about how the brain perceives the body. “Body image turns out to be extraordinarily plastic,” Ramachandran told Science News. “We think of ourselves as stable people with a stable body image — but we can inhabit a body that cannot exist in the physical world.”


POWER WORDS (adapted from the Yahoo! Kids Dictionary)

neuroscience Science that deals with the nervous system and brain.

amputee A person who has had one or more limbs removed.

perceive To become aware of directly through any of the senses, especially sight or hearing.

phantom pain Pain or discomfort felt by an amputee in the area of the missing limb.

anorexia nervosa A psychophysiological disorder usually occurring in young women that is characterized by an abnormal fear of becoming obese, a distorted self-image, a persistent unwillingness to eat, and severe weight loss. It is often accompanied by self-induced vomiting, excessive exercise, malnutrition, amenorrhea and other physiological changes

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