Scientists able to decode `internal voices`

London: Scientists have developed a striking method that can reconstruct words based on the brain waves of patients thinking of those words, a technique they say could soon help comatose and locked-in patients communicate.

Devised by researchers at the University of California, the technique relies on gathering electrical signals directly from patients` brains.

Based on the signals from listening patients, a computer model was used to reconstruct the sounds of words that they were thinking of, the researchers said.

While several approaches have in recent years suggested that scientists are closing in on methods to tap into our very thoughts, the latest study, reported in PLoS Biology, achieved its result by implanting electrodes directly into a part of participants` brains, the BBC News reported.

In a 2011 study, participants with electrodes in direct brain contact were able to move a cursor on a screen by simply thinking of vowel sounds.

By studying patterns of blood flow related to particular images, a group led by Jack Gallant at the University of California Berkeley showed that patterns can be used to guess images being thought of -- recreating "movies in the mind".

Now, another UC Berkeley team led by Dr Brian Pasley has taken that "stimulus reconstruction" work a step further.

"This is inspired by a lot of Jack`s work," Dr Pasley said. "One question was... how far can we get in the auditory system by taking a very similar modelling approach?"

The team focused on an area of the brain called the superior temporal gyrus, or STG, that help us make linguistic sense of the sounds we hear.

The team monitored the STG brain waves of 15 patients who were undergoing surgery for epilepsy or tumours, while playing audio of different speakers reciting words and sentences.

The trick is disentangling the chaos of electrical signals that the audio brought about in the patients` STG regions. To do that, the team employed a computer model that helped map out which parts of the brain were firing at what rate, when different frequencies of sound were played.

With the help of that model, when patients were presented with words to think about, the team was able to guess which word the participants had chosen.
They were even able to reconstruct some of the words, turning the brain waves they saw back into sound on the basis of what the computer model suggested those waves meant.

"There`s a two-pronged nature of this work -- one is the basic science of how the brain does things," said senior study author Robert Knight.

"From a prosthetic view, people who have speech disorders could possibly have a prosthetic device when they can`t speak but they can imagine what they want to say," Prof Knight said.

"The patients are giving us this data, so it`d be nice if we gave something back to them eventually."

However, the authors said that the thought-translation idea is still to be vastly improved before such prosthetics become a reality.