A sound sense of illusion

EVEN IF you don't care much for football, there's one aspect of the World Cup that won't have passed you by: the buzzing of the vuvuzela horns played by fans is the droning soundtrack to the event, writes CLAIRE 'CONNELL

At least you can mute the sound on the television, but imagine if you couldn’t. People with tinnitus perceive buzzing, ringing, whistling or other sounds that don’t come from an external source and in severe cases it can affect quality of life.

“You can’t turn it off, it follows you everywhere,” says Dr Ross O’Neill, a research fellow in the Hamilton Institute at NUI Maynooth.

His research is coming up with a new way to tackle the condition – by sending signals to the brain through the tongue. It might sound like an unusual approach, but there’s method to it.

In tinnitus, the illusory noise often starts when noise damage to the ear or age-related hearing loss means there’s a drop in the levels of real sound being picked up and the brain tries to compensate, explains O’Neill.

“I call it ‘running the pump dry’. If you imagine an electrical pump that’s sucking up water and then you starve the pump of its water supply it starts to oscillate in a desperate attempt to suck up more water,” he says.

“It’s essentially the same thing happening with tinnitus: the amount of sound going through the ear has dropped and in an attempt to maintain the levels of information [the brain] fills the gaps with noise.”

One treatment approach is to push more information in through the ear using hearing aids, but it hasn’t been hugely successful, according to O’Neill.

“[In tinnitus] the water supply pipe to the pump is narrowed, so you can only push a certain amount of information down that pipe. That’s why hearing aids haven’t been terribly effective,” he says.

Instead the new device, Mutebutton, is looking to run a second “pipe” of information into the brain by engaging another sensory mechanism – touch.

The approach converts a piece of music into a tactile message that’s delivered to the user’s tongue at the same time that their ears hear the sound version.

“It’s similar to braille displays, we are displaying those patterns on the tongue using an electrotactile array,” says O’Neill, who yesterday won the One to Watch award at Enterprise Ireland’s Applied Research Forum.

In practice, the user would spend about half an hour sensing a piece of music – Bach is good, according to O’Neill because it uses a range of notes – through their ears and tongue at the same time.

“They would play music through the speakers to their ears and simultaneously through our device to the tongue as tactile patterns,” says O’Neill, who is collaborating on the project with consultant ear, nose and throat (ENT) surgeon Brendan Conlon.

The idea is to stimulate multi-sensory integration (MSI) centres in the brain and get them to tell the difference between the real noise of the music and the illusory noise in tinnitus.

“The problem with tinnitus is that the brain cannot tell the difference between real sounds and imaginary ones because they are both coming from the ear and it trusts the ear,” says O’Neill.

“We are giving these MSI centres a checklist of real sounds so that they can compare and contrast the signals and then isolate the illusory sound, the tinnitus sound, and suppress it through adaptation.”

The project – which is being supported by Enterprise Ireland, Science Foundation Ireland, the National Digital Research Centre and the Higher Education Authority – is ramping up to start human trials and ultimately to commercialise the Mutebutton device.

“We would say the treatment would take maybe a number of months, maybe even longer, you might just continue to treat it,” says O’Neill.

“But it has a low personal impact and people could use it for half an hour or an hour each day in their own home and on their own schedule.”