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Researchers translate brain signals using microelectrodes

Utah University researchers have translated brain signals into words using two grids of 16 microelectrodes implanted on top of the brain of a patient.

The move is a first step towards the development of a system that might, one day, allow severely paralysed people to speak with their thoughts.

’We have been able to decode spoken words using only signals from the brain with a device that has promise for long-term use in paralysed patients who cannot now speak,’ said Bradley Greger, an assistant professor of bioengineering at the university.

As the method involves placing electrodes on the brain and still needs improving, he expects it will be a few years before clinical trials will take place on paralysed people who are unable to speak.

In a trial, the university research team placed grids of tiny non-penetrating microelectrodes called microECoGs over speech centres in the brain of a volunteer with severe epileptic seizures. The man already had a craniotomy – temporary partial skull removal – so doctors could place larger, conventional electrodes to locate the source of his seizures and surgically stop them.

Since the microelectrodes do not penetrate brain matter, they are considered safe to place on speech areas of the brain – something that cannot be done with penetrating electrodes that have been used in experimental devices to help paralysed people control a computer cursor or an artificial arm.

Using the experimental microelectrodes, the scientists recorded brain signals as the patient repeatedly read each of 10 words that might be useful to a paralysed person: ’yes’, ’no’, ’hot’, ’cold’, ’hungry’, ’thirsty’, ’hello’, ’goodbye’, ’more’ and ’less’.

Later, they tried figuring out which brain signals represented each of the 10 words. When they compared any two brain signals – such as those generated when the man said the words ’yes’ and ’no’ – they were able to distinguish brain signals for each word 76 per cent to 90 per cent of the time.

When they examined all 10 brain signal patterns at once, they were able to pick out the correct word that any one signal represented only 28 per cent to 48 per cent of the time – better than chance (which would have been 10 per cent) but not good enough for a device to translate a paralysed person’s thoughts into words spoken by a computer.

’This is proof of concept. We’ve proven these signals can tell you what the person is saying well above chance,’ said Greger. ’But we need to be able to do more words with more accuracy before it is something a patient really might find useful.’

This photo shows two kinds of electrodes sitting atop a severely epileptic patient’s brain after part of his skull was removed temporarily. The larger, numbered, button-like electrodes are ECoGs used by surgeons to locate and then remove brain areas respo

This photo shows two kinds of electrodes sitting atop a severely epileptic patient’s brain after part of his skull was removed temporarily. The larger, numbered, button-like electrodes are ECoGs used by surgeons to locate and then remove brain areas responsible for severe epileptic seizures. While the patient had to undergo that procedure, he volunteered to let researchers place two small grids – each with 16 tiny microECoG electrodes – over two brain areas responsible for speech. These grids are at the end of the green and orange wire bundles, and the grids are represented by two sets of 16 white dots since the actual grids cannot be seen easily in the photo. Utah University scientists used the microelectrodes to translate speech-related brain signals into actual words – a step towards future machines that will allow severely paralysed people to speak.

 


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