From the New Scientist
THIS WEEK: FRONTIERS. p24 17 Mar
01
#45 Suck it and see
Your tongue could give you a whole new sense of direction
Caroline Seydel
HOW do you find your way around when it's pitch dark ? You could
try sucking on an electrode that transmits visual cues to your
brain via your tongue. Its developers hope that some day the
system could help blind people get about easier.
Paul Bach-y-Rita and Kurt Kaczmarek of the University of
Wisconsin in Madison have developed a device they call a 'tongue
display unit' - a grid of 144 gold-plated electrodes covering an
area a little larger than a postage stamp. In one prototype, a
video camera feeds signals to the TDU via a small box of
electronics.
Cheryl Schiltz tested the tongue display by using it to navigate
a computer maze. With her eyes closed, she pushed buttons to move
through the maze as directed by the computer. To signal her to
turn left, the leftmost electrodes tingled her tongue. To go
straight, the tingling pulsed from back to front. 'It was just
amazing,' she says. 'Just by feeling it on my tongue, my brain
got the message where to go.'
The human tongue is highly sensitive to touch because it contains
a high density of nerve fibres and mechanosensors. 'It also
presents an electrical resistance that's consistent over time,'
says Kaczmarek. A large part of the brain's cortex is devoted to
the sensory perception of the tongue. And because the tongue is
awash with conductive saliva, it is an efficient surface for
delivering electrical impulses - unlike exposed skin, which is
covered with a layer of dead skin cells and can go from sweaty to
dry in minutes.
It takes 50 hours of practice to become familiar with the unit,
says Bach-y-Rita. Quite quickly, people stop noticing the weird
sensation and learn how to interpret it, similar to the way
people learn Braille.
So far the unit has been used to convey very simple information,
such as computer-generated graphics. But within five years, the
researchers expect to condense the system into an inconspicuous
unit that fits in the user's mouth, with a wireless link from a
spectacle-mounted video or infrared camera. For underwater use,
it could be linked to a sonar sensor. US Navy diving teams have
already tested a system in murky waters.
An orientation feedback system to assist people who have lost
their sense of balance may also be on the horizon. Head-mounted
accelerometers would sense roll and pitch so that when the user
wobbles, the system signals to correct left or right.
Schiltz says the TDU produces a 'fizzy' sensation, that some
people may dislike. 'It's kind of like when you stick your tongue
on a 9-volt battery,' she says. 'But not as scary.'
For more science news see http://www.newscientist.com
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Copyright 2001 New Scientist, Reed Business Information
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