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2012-02-01 09:16:02
By Jason Palmer Science and technology reporter, BBC News
Researchers have demonstrated a striking method to reconstruct words, based on
the brain waves of patients thinking of those words.
The technique reported in PLoS Biology relies on gathering electrical signals
directly from patients' brains.
Based on signals from listening patients, a computer model was used to
reconstruct the sounds of words that patients were thinking of.
The method may in future help comatose and locked-in patients communicate.
Several approaches have in recent years suggested that scientists are closing
in on methods to tap into our very thoughts.
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.
A technique called functional magnetic resonance imaging to track blood flow in
the brain has shown promise for identifying which words or ideas someone may be
thinking about.
By studying patterns of blood flow related to particular images, Jack Gallant's
group at the University of California Berkeley showed in September that
patterns can be used to guess images being thought of - recreating "movies in
the mind".
All in the mind
Now, Brian Pasley of the University of California, Berkeley and a team of
colleagues have taken that "stimulus reconstruction" work one step further.
Continue reading the main story
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The development of direct neuro-control over virtual or physical devices
would... improve quality of life immensely for those who suffer from impaired
communication skills
Mindy McCumber Florida Hospital
"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.
This broad region is not just part of the hearing apparatus but one of the
"higher-order" brain regions 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 a number 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.
Plots of predicted spectrograms (PLoS Biology) The technique hinges on plotting
brain activity across a number of frequencies
"There's a two-pronged nature of this work - one is the basic science of how
the brain does things," said Robert Knight of UC Berkeley, senior author of the
study.
"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 explained.
"The patients are giving us this data, so it'd be nice if we gave something
back to them eventually."
The authors caution that the thought-translation idea is still to be vastly
improved before such prosthetics become a reality.
But the benefits of such devices could be transformative, said Mindy McCumber,
a speech-language pathologist at Florida Hospital in Orlando.
"As a therapist, I can see potential implications for the restoration of
communication for a wide range of disorders," she told BBC News.
"The development of direct neuro-control over virtual or physical devices would
revolutionise 'augmentative and alternative communication', and improve quality
of life immensely for those who suffer from impaired communication skills or
means."