Walking and Balance: Stimulation Of The Semicircular Canals Can Artificially Con

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Stimulation Of The Semicircular Canals Can Artificially Control Human

Walking And Balance

http://www.medicalnewstoday.com/medicalnews.php?newsid=49095

By applying electrical currents across the heads of people while they

walk, researchers have improved our understanding of how our

vestibular system helps us maintain upright posture; at the same

time, the researchers found that the stimulus could be applied in a

way that allowed a person who was walking straight ahead to be

steered by " remote control " without her balance being affected. The

findings are reported by Fitzpatrick and Jane E. of

the Prince of Wales Medical Research Institute and the University of

New South Wales, Australia, and L. Day of University College

London in the August 8th issue of Current Biology, published by Cell

Press.

To investigate how the body's ability to sense head movements can

contribute to balance control and guidance control--two critical

aspects of bipedal locomotion--the researchers stimulated nerves that

normally communicate signals from the so-called semicircular canals,

structures that are part of the vestibular system that assists in

orientation and balance. The researchers found that artificial

stimulation of semiciruclar canal nerves afforded " remote control "

that was accurate enough to keep subjects on pathways and avoiding

obstacles while walking blindfolded through botanical gardens. The

researchers also found that with a subject's head in another

position, exactly the same stimulus could be used to disturb upright

balance, causing the subject to lean in one direction or the other,

but without having any effect on steering his walking.

Known as bipedalism, our habitual upright posture is unique in the

animal kingdom and has arisen through specific complementary

adaptations of the body and brain. It has been believed that the key

to human balance has come from a precise sense of--and ability to

align the body to--the direction of gravity.

However, the semicircular canals that the researchers stimulated to

control walking and balance detect rotational movements of the head,

not the direction of gravity. These findings therefore show that

sensing movement is crucial for our upright posture.

The findings support interpretations made from fossil evidence of an

evolutionary change in the development of the human semicircular

canals. These evolutionary changes would allow for enhanced movement

detection, and therefore also indicate that that controlled movement,

rather than alignment to gravity, has been important for the

development of modern human bipedalism.

This new work has important implications for understanding how the

brain processes sensory signals.

According to the researchers, the findings indicate that from the

single sensory organ that signals the movement of the head, the brain

makes instant complex " mathematical " calculations to discard the

parts not important to balance or steering, such as the movements we

make when looking around, and then transforms the remaining signal

into two components. One component is used to control steering, and

the other to control balance. In a more practical view, this ability

to produce illusions of movement, and then steer and balance the body

by external control, leads the researchers to expect that stimulation

techniques developed from the approach used in the new study will

lead the way to diagnostic, therapeutic, and virtual-reality

applications.

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The researchers include C. Fitzpatrick and Jane E. of

Prince of Wales Medical Research Institute and University of New

South Wales in Sydney, Australia; L. Day of University College

London in London, United Kingdom.

This study was supported by the National Health and Medical Research

Council of Australia and the Medical Research Council of Great

Britain.

Fitzpatrick et al.: " Resolving Head Rotation for Human Bipedalism. "

Publishing in Current Biology 16, 1509-1514, August 8, 2006, DOI

10.1016/j.cub.2006.05.063 http://www.current-biology.com/