Speaking in Tongues

by Alexander Gelfand
Sept. 2, 2008

TongueDriveTHE tongue is the strongest muscle in the human body. It is also the one through which people usually make their wishes known. And that role is about to be extended. Maysam Ghovanloo, an engineer at the Georgia Institute of Technology, has developed what he calls the Tongue Drive, a collection of magnets, sensors and wireless electronic equipment that allows a disabled user to make his wishes known to an electric wheelchair or a computer by moving his tongue. Dr Ghovanloo chose the tongue as his joystick because it is agile, slow to fatigue and rarely affected by spinal cord injury or neuromuscular disease. (It is attached to the brain by the hypoglossal cranial nerve rather than via the spinal cord.)

The core of the device is a lentil-sized magnet that is temporarily attached to the user's tongue. An array of magnetic sensors mounted on a headset reads the position of this magnet in three dimensions and transmits that information wirelessly to a laptop computer. Specialised software then distinguishes the different tongue gestures from one another, correlates them with various commands (go forward, turn left, single-click, double-click etc), and issues those commands, again wirelessly, to the appropriate recipient device.

According to Susan Howley of the Christopher and Dana Reeve Foundation, which helped to pay for Dr Ghovanloo's work, such "assistive" technologies are proliferating as researchers realise that extending the abilities of individuals suffering from spinal cord injury by small increments is easier than finding a miracle cure. In this context, the Tongue Drive has several advantages over its rivals. Brain-computer interfaces that read nerve impulses, for example, are slow and require cumbersome arrays of electrodes to be fitted to the patient's scalp or to be implanted in his brain. Devices that track eye, head or neck movement can interfere with normal vision and need the user to remain stationary. And the ubiquitous sip-and-puff system, which requires the user to blow or suck on a plastic tube, accepts only four basic commands.

In contrast, the Tongue Drive is unobtrusive, accurate, and can accept a large number of different commands. Tests on able-bodied Georgia Tech students have been sufficiently encouraging to attract two companies interested in licensing the technology, and Dr Ghovanloo intends to begin testing the idea on disabled people later this year. If all goes well, a production version of the device could come to market within 18 months, at a cost below $10,000.

Georgia Tech is not the only organisation to think of using the tongues of the paralysed to improve their lives. Think-A-Move, a firm based in Ohio, already has a different system on the market. Instead of magnets, Think-A-Move's technology uses a tiny microphone embedded in an earphone. This reads the pressure changes that occur in the inner ear as the tongue moves. Different tongue gestures can be distinguished by the waveforms of these pressure changes, and those gestures thus used to control machines. A system configured to control an electric wheelchair can be purchased for less than $6,000. Unlike the Tongue Drive, however, Think-A-Move's tongue-control technology works best when the user is reasonably still, and it recognises only eight to ten commands.

Moving and communicating are not the only things that the severely disabled care about, however. According to a paper published four years ago in the Journal of Neurotrauma, recovering sexual function is also a priority. Accordingly, Jaimie Borisoff, a neuroscientist at the Neil Squire Society Brain Interface Laboratory in Vancouver, British Columbia, is using the tongue to restore sexual sensation to those who cannot feel anything from the neck down.

Dr Borisoff employs an electrode-laden device known as the BrainPort, which is made by an American firm called Wicab, to pump emulated sensory signals through the tongue to the brain (the tongue's nerves lie close to its surface and saliva is an excellent conductor of electrical signals). These signals can, for example, induce the feeling of "relative motion" experienced during masturbation. According to Dr Borisoff, his method has led to "definite improvement in the overall sexual experience" of at least one patient who has complete sensory loss. Dr Borisoff hopes that after a paralysed person has trained with the device for some time, he might once again experience orgasm—and continue to do so "when not even using the equipment". That would set a few tongues wagging.

Copyright ©2008 Alexander Gelfand

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