News in Science

Ballerina brain holds secret to balance

Round and round Years of training cause structural changes in a ballet dancer's brain that help them stay balanced in the pirouette, suggests a new study.

The finding, reported in the journal Cerebral Cortex, may aid the treatment of chronic dizziness.

Brain scans of professional female ballet dancers revealed differences from other people in two parts of the brain: one that processes input from the balancing organs in the inner ear, and another responsible for the perception of dizziness.

Most people, after turning around rapidly, feel dizzy for a period thereafter.

This is because of the fluid-filled chambers of the ear's balance organs, which sense the rotation of the head through tiny hairs that perceive the fluid swishing about. The fluid continues to move for a while after the spin -- which creates the perception that one is moving when still -- hence the dizziness.

Ballet dancers can perform multiple pirouettes with little or no feeling of dizziness -- a feat that has long puzzled researchers.

The pirouette sees a dancer execute one or more full-body turns on the toe or ball of one foot.

"Ballet dancers seem to be able to train themselves not to get dizzy, so we wondered whether we could use the same principles to help our patients," says Dr Barry Seemungal from the Department of Medicine at Imperial College London.

For the study, Seemungal and colleagues spun 29 ballerinas around in a rotating chair in a dark room, and did the same with 20 female rowers of similar age and fitness levels.

The women were asked to turn a lever on a small wheel attached to their chair in rhythm with the spinning sensation they experienced after the chair was brought to a halt.

For the dancers, the perception of spinning lasted for a "significantly" shorter period.

The researchers also looked at the women's brains with MRI (magnetic resonance imaging) scans.

They found that the part of the cerebellum that processes the signal from the balancing organs, was smaller in the dancers. The cerebellum is the part of the brain that governs body movement.

"It's not useful for a ballet dancer to feel dizzy or off balance," says Seemungal.

"Their brains adapt over years of training to suppress that input" -- allowing them to continue dancing after spinning around in a pirouette and complete a performance without losing their balance.

"If we can target that same brain area or monitor it in patients with chronic dizziness, we can begin to understand how to treat them better."

About one in four people suffer chronic dizziness at some time in their lives.