September 27, 2013
Spinning Doesn’t Dizzy Ballerinas Due To Brain Conditioning
Brett Smith for redOrbit.com - Your Universe Online
Spinning around in circles causes dizziness in most people, which could be a problem for figure skaters or ballerinas who must perform several spins during a typical routine.
The dizziness sensation is caused by the fluid-filled vestibular organs located in the inner ear. Through the use of tiny hairs, these organs sense the body’s movement and provide a sense of balance. After turning around rapidly then stopping, the fluid in these organs continues to slosh around causing the sensation of movement.
While some ballet dancers use a technique called spotting, which involves fixing their gaze on the same spot while spinning, to reduce dizziness – the new study showed that these dancers have conditioned their brains’ to reduce sensory input from the vestibular organs.
In the study, researchers enlisted a group of 29 female ballet dancers and a group of 20 female rowers with matching levels of fitness and age.
The participants were rapidly spun around in a dark room and then quickly stopped. They were then asked to turn a handle in sync with how they felt they were still spinning. The researchers also recorded participants’ eye reflexes as affected by sensory input from the vestibular organs. Finally, the participants' brain structures were imaged using an MRI machine.
Based on these observations, the ballet dancers showed that they experienced a spinning sensation for much less time than the rowers.
"Dizziness, which is the feeling that we are moving when in fact we are still, is a common problem,” said Dr Barry Seemungal, from the Department of Medicine at Imperial College London. “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."
The brain images showed differences between the two groups in an area where sensory input from the vestibular organs is processed. This area in the cerebellum was smaller in dancers than it was in the rowers.
"It's not useful for a ballet dancer to feel dizzy or off balance,” explained Seemungal. “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.”
“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,” he added.
The researchers also found the perception of spinning closely matched the eye reflexes triggered by vestibular signals in the rowing group, but the two were uncoupled for the dancers.
"This shows that the sensation of spinning is separate from the reflexes that make your eyes move back and forth," Seemungal said. "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. You need to look at tests that assess both reflex and sensation."