Differences in the brain structure of ballet dancers found by scientists may be helping them circumvent feeling dizzy when they perform pirouettes.
Many years of training, the research suggests, can permit dancers to suppress signals from the inner ear’s balance organs.
These are interesting findings, because they could lead to improved treatment for patients with chronic dizziness, which includes vertigo and lightheadedness. Approximately one out of four people experience the condition some time in their lives.
A Place Called Vertigo
Usually, the feeling of dizziness starts in the vestibular organs of the inner ear. These fluid-filled chambers sense rotation of the head through tiny hairs that sense the fluid moving. After turning around rapidly, the fluid continues to move, which can make you feel like you’re still spinning.
How can ballet dancers perform multiple pirouettes with little or no feeling of dizziness? The findings show that this isn’t just due to spotting. Spotting is the technique dancers use that involves rapidly moving the head to fix their gaze on the same spot as much as possible.
Rowers vs. Dancers
Imperial College London researchers enlisted 29 female ballet dancers and, as a comparison group, 20 female rowers whose age and fitness levels matched the dancers’.
The volunteers were spun around in a chair in a dark room. They were asked to turn a handle in time with how quickly they felt like they were still spinning after they had stopped.
The researchers also measured eye reflexes triggered by input from the vestibular organs. Later, they examined the participants’ brain structure with MRI scans.
In dancers, both the eye reflexes and their perception of spinning lasted a shorter time than in the rowers.
Dancers in Training
“Dizziness, which is the feeling that we are moving when in fact we are still, is a common problem”, said Dr Barry Seemungal. “ 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.”
Brain scans showed differences between the groups in two parts of the brain: an area in the cerebellum where sensory input from the vestibular organs is processed and in the cerebral cortex, which is responsible for the perception of dizziness.
The area in the cerebellum was smaller in dancers. Dr Seemungal thinks this is because dancers would be better off not using their vestibular systems, relying instead on highly co-ordinated pre-programmed movements.
“It’s not useful for a ballet dancer to feel dizzy or off balance,” he explained. “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.”
Spinning is not a Reflex
Another finding in the study may be important for how chronic dizzy patients are tested in the clinic.
In the control group, the perception of spinning closely matched the eye reflexes triggered by vestibular signals, but in dancers, the two were uncoupled.
“This shows that the sensation of spinning is separate from the reflexes that make your eyes move back and forth,” Dr 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.”
Y Nigmatullina et al.
‘”The Neuroanatomical Correlates of Training-Related Perceptuo-Reflex Uncoupling in Dancers
Cerebral Cortex, 27 September 2013. doi:10.1093/cercor/bht266