Air Date: Week of December 2, 2005

Living on Earth’s Emily Torgrimson reports on a new study showing that a person’s perception of being fat or thin may be traced to a distortion in a specific part of the brain.

Transcript

CURWOOD: It’s Living on Earth. I’m Steve Curwood and coming up: Why the mall is where it’s at. First this Note on Emerging Science from Emily Torgrimson.

[SCIENCE NOTE THEME]

TORGRIMSON: ‘Honey, does this make me look fat?’ Don’t go there, people…into that dead-man’s land, the fragile netherworld of body image. Especially because what your partner sees in the mirror may be a mirage. According to a new study led by University College London, feeling fat – or thin – is a construct of the brain.

To identify which parts of the brain involve body image, scientists tricked patients into believing their waists were shrinking using a technique called the “Pinocchio Illusion.” Scientists attached a vibrating device to volunteers’ wrists, which simulates the sensation of the wrist flexing inward. With their hands resting on their waists, volunteers all felt that their waist had shrunk by up to 28 percent.

At the same time, scientists found high activity levels in the posterior parietal cortex, the part of the brain that integrates sensory information from all over the body. The subjects who reported the strongest shrinking sensation also demonstrated the strongest activity in this part of the brain.

Though we process information about our body size and shape every day, there’s no specialized receptor, like the nose for smell. The information comes from various sources – our skin, joints, muscles, our vision – and the brain appears to synthesize these sources into a map; a sketch of our body.

The goal for scientists is to see if people with anorexia or body dysmorphic disorder – people who over- or underestimate their body size, or focus on a small or imagined flaw – if they too experience distortion in this part of the brain. That’s this week’s Note on Emerging Science. I’m Emily Torgrimson.