Watching a ballerina perform pirouettes is an awe-inspiring experience that can make your head spin. But new research suggests that differences in their brain structure enables ballet dancers to avoid feeling dizzy by suppressing signals from balance organs located in the inner ear.
The researchers, from Imperial College London, published their results in Cerebral Cortex, and they hope their findings may help with treatment for patients who suffer from chronic dizziness.
Dizziness, say the researchers, comes from vestibular organs in the inner ear, where these fluid-filled compartments sense rotation of the head with tiny hairs that perceive movement of the fluid.
They note that after spinning quickly, the fluid continues to move, giving the impression that the head is still turning.
Ballet dancers, however, are able to perform pirouette after pirouette - a full spin of the body executed on the point of the toe or the ball of the foot.
Mikhail Baryshnikov demonstrates multiple pirouettes in a 1980s production of Don Quixote at the American Ballet Theatre:
The researchers say ballet dancers are able to perform these multiple pirouettes with little or no dizziness because of brain changes brought about through years of training.
Brain differences in dancers
To arrive at their findings, the team in the UK analyzed 29 female ballet dancers who had an average of 16 years' ballet training, as well as a control group of 20 female rowers with similar ages and fitness levels as the dancers.
After spinning them around in a chair with the lights out, the researchers asked the participants to turn a handle in time with how fast they felt like they were still spinning. Additionally, they measured eye reflexes that are triggered by input from the vestibular organs.
The eye reflexes and spinning perception lasted a shorter time for the dancers than for the rowers, researchers observed.
Dr. Barry Seemungal, from the Department of Medicine at Imperial College London, said:
"I see a lot of patients who have suffered from dizziness for a long time. 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."
After examining brains of both the rowers and the dancers with MRI scans, the team found that there were differences in two parts of the brain:
- An area in the cerebellum that processes sensory input from the vestibular organs, and
- The cerebral cortex, an area responsible for the perception of dizziness.
In the dancers, the area in the cerebellum was smaller, which Dr. Seemungal attributes to dancers being better off by not using their vestibular systems and relying on pre-programmed movements.
Dr. Seemungal says:
"It's not useful for a ballet dancer to feel dizzy or off balance. Their brains adapt over years of training to suppress that input. Consequently, the signal going to the brain areas responsible for perception of dizziness in the cerebral cortex is reduced, making dancers resistant to feeling dizzy."
He adds that if his team is able to target this same area in patients with chronic dizziness, they would be able to find ways to treat them better.
Potential treatment for chronic dizziness
How patients with chronic dizziness are tested in the clinic may be altered, after another finding in the study shed light on how eye reflexes are triggered.
The researchers say that in the control group, the perception of spinning matched the eye reflexes triggered by vestibular signals. In the dancers, however, these two elements did not match.
Dr. Seemungal explains what this means:
"This shows that the sensation of spinning is separate from the reflexes that make your eyes move back and forth. In many clinics, it's common to only measure the reflexes, meaning that when these tests come back normal the patient is told that there is nothing wrong. But that's only half the story."
He says clinics should look at tests that analyze "both reflex and sensation."
The researchers conclude their study by noting that understanding the brain mechanisms that underlie vestibular adaptation is very important for the treatment of patients with chronic disorders of vestibular organs.