Palatable monitor makes it good to talk

August 23, 1996

One in every 600 children born in the United Kingdom has a cleft palate or cleft lip, which can lead to speech problems. Most of them respond well to conventional speech therapy, but those with intractable difficulties can be helped by Electropalatography (EPG), which records the contact between the tongue and the palate.

Bill Hardcastle, head of the department of speech and language sciences at Queen Margaret College in Edinburgh said: "You don't know what the tongue's doing in the mouth, but with EPG, as you talk, you see it displayed on a computer screen."

The patient wears a customised artificial palate, like a very thin denture without the teeth, which contains 62 miniature sensors linked to a computer. When the tongue touches the sensors, the patterns displayed on screen can be used to diagnose speech problems, and normal speech patterns can be displayed alongside these, allowing the patient to see clearly where the tongue should be.

"If there are abnormal tongue movements, the children can use the visual feedback and change their contact patterns," says Professor Hardcastle.

Queen Margaret is a centre of expertise in EPG, which can help patients with a range of speech disorders, including those recovering from a stroke. It recently won funding from the Scottish Office department of health for a two-year training scheme which will make EPG therapy available at speech therapy centres across Scotland.

But the department of speech and language sciences has now set up a state of the art system for analysing the mechanisms of speech, the first of its kind in the United Kingdom, which moves from the current one-dimensional picture of tongue movement to three dimensions. This links the EPG technique to another method of tracking movement during speech, Electromagnetic Articulography (EMA), which can plot the movement of the tongue, lips and jaw.

The new facility, backed by a Pounds 1,000 grant from the Scottish Higher Education Funding Council's regional strategic initiatives fund, will be used jointly by the Queen Margaret department and Edinburgh University's department of linguistics and centre for speech technology research. It includes a high-speed computer link through the local Metropolitan Area Network to a dedicated computer at Edinburgh.

The EPG system works only when the tongue touches the palate, and therefore gives few clues as to what is happening during vowel sounds, or how the tongue is moving generally. But the EMA system uses a helmet with three electromagnets which send currents through small coils attached to the tongue and lips.

"When they move, an electromagnetic field creates a voltage which can be detected by computer, and while the person is speaking, you can see how the tongue moves backwards and forwards and up and down, including the parts of the tongue you can't see with EPG," says Professor Hardcastle.

"It's plotting the movement of the tongue, lips and jaws," says Fiona Gibbon, a lecturer in the department who is also a speech and language therapist. "We're seeing the acceleration and velocity of each of the coils, and building up a much more complex picture."

Until now, charting the trajectory of the tongue has only been possible through cine X-rays, a complex and potentially harmful procedure, or through magnetic resonance imaging, which forces the subject to hold a particular position, such as forming the letter "S", over a number of seconds rather than actually speaking. EMA allows the researchers to record hours of data in real time, linking an acoustic recording to a visual display of speech movement.

When people are speaking, there are many simultaneous movements of the tongue, jaw and lips, but speech problems can lead to a breakdown in this coordination. Discovering how the tongue moves during normal speech will allow the researchers to make predictions which could help therapists to use EPG more effectively.

"We're also interested in speech as a skilled motor activity. We've got a reasonable knowledge of things like locomotion and the biomechanics involved in that, but we haven't got a very clear idea of speech because it's very difficult to measure the organs," says Professor Hardcastle, adding that an EMA coil can even be attached to the soft palate "if you're brave".

But at present, the research team is searching for continued funding after the SHEFC grant runs out.

"The combination of EMA and EPG really gives us a unique insight into the nature of the speech process, and we would like to extend this for at least another year," he says.

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