Listening for balance

[Guest guest]

Listening for balance

A device that's worn like a pager may help correct balance problems

by signaling when the wearer starts to sway.

By Marsa, Special to The Times

http://www.latimes.com/features/health/la-he-lab1aug01,1,1348712.story

Standing up straight and keeping your body centered may seem like

second nature to most of us. But for people with balance disorders,

it is anything but easy. Wobbly and unsure on their feet, they often

have difficulty walking and are prone to falls, a leading cause of

injury and death in the elderly.

Certain diseases and medications, or the normal wear and tear of

aging, can weaken the sensory signals transmitted to the part of the

brain that governs gravitational stability, which is why people

become unsteady, dizzy or disoriented.

Now scientists have developed a novel balance feedback device that

weighs less than a pound and can be worn on a belt like a pager. It

may help correct balance difficulties by providing sufferers with the

sensory data they are missing.

" Balance disorders can be terribly social-stigmatizing because people

think they're drunk, and some people withdraw from daily activities

because they're afraid of falling, " says Platt, program

director for balance and vestibular sciences for the National

Institute on Deafness and Other Communication Disorders in Bethesda,

Md. " A device that accelerates someone's ability to retrain

themselves holds a lot of promise. "

An estimated 20% of Americans suffer from balance disorders. These

difficulties can be triggered by viral infections, head injuries,

aging, illnesses such as multiple sclerosis and Parkinson's disease,

or inner ear damage, which can be caused by Ménière's disease, poor

blood circulation or some antibiotics.

Although maintaining balance may seem effortless, keeping your body

stable is a gravity-defying skill that requires input from three main

senses, says Fay Horak, a neuroscientist who helped develop the new

technology at the Oregon Health and Science University in Beaverton.

The brain integrates information from our vision, from the vestibular

(balance) system in the inner ear and from the somatosensory system —

the sense receptors in our muscles, joints, skin and feet — that

tells us where our body is in reference to surfaces that we contact.

Most people sway slightly when they're standing still. " You think you

are totally frozen, but your body is making little movements that

your brain controls to maintain your balance, " says Marco Dozza, a

biomedical engineer at the University of Bologna in Italy, who is

part of the OHSU research team.

If a person doesn't receive enough information from the innate

balance sensors, especially from the vestibular system that regulates

our sense of gravity, he or she can become quite wobbly without

realizing it. As a consequence, he may tilt too far and topple

over. " It's basic physics, " says Dozza. " The bigger the sway, the

more likely it is to fall. "

The auditory balance feedback device can help rehabilitate a person's

damaged sensory system. The lightweight appliance, which contains

sensors, is hooked to a belt and connected to a pair of headphones.

The device acts much like a carpenter's level and emits auditory cues

to let users know when their body is swaying too much so they can

make corrections. Different tones and intensities tell subjects which

way they are leaning: a high-pitched tone, for example, signals that

they are leaning forward and grows louder if they bend farther; a

lower sound tells them they're swaying backward.

" People intuitively learn how to use the device in about a minute,

and it's all very natural, " Horak says. " The brain immediately

integrates the information with other sensory input. "

Results of a study this year were encouraging. The research involved

nine volunteers who suffered from such severe balance problems that

they had trouble standing on a piece of foam without losing their

balance. While using the feedback device, the participants decreased

their sway area by 23%, reduced their body movements by 46% and

increased time spent within their safety zone by 195%.

OHSU researchers are now doing follow-up studies to determine how

long the effect of the balance training device lasts. " We'd like to

use this not just for rehabilitation but as a prosthetic that can

help people in their daily lives, " Horak says.

The next step for Horak and her colleagues is to demonstrate that the

device can actually help people walk — a far more complex task than

helping people stand up straight.

Other tools to improve balance are under development.

Scientists at the University of Wisconsin in Madison have developed

the BrainPort, a sensory substitution device that studies show can

deliver missing sensory data through an electronic strip placed on

the tongue. The patient wears a helmet embedded with microsensors.

When the patient's head moves, the microsensors send a signal to

electrodes on the tongue, creating a light buzzing sensation. The

location of the buzz on the tongue tells the brain what position the

head is in.

And Boston University researchers are testing a foot vibrator. The

noise from the vibration amplifies weak signals and makes the nerves

in the feet more sensitive to the pressure changes that occur when

the body moves. A 2003 study showed that the device improved balance

in a dozen healthy 75-year-olds, whose body sway became comparable to

23-year-olds' in the study's control group.

— Marsa