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Scientists have developed a computerised mind-reading technique which
lets them accurately predict the images that people are looking at by
using scanners to study brain activity.
The breakthrough by
American scientists took MRI scanning equipment normally used in
hospital diagnosis to observe patterns of brain activity when a subject
examined a range of black and white photographs. Then a computer was
able to correctly predict in nine out of 10 cases which image people
were focused on. Guesswork would have been accurate only eight times in
every 1,000 attempts.
The study raises the possibility in the
future of the technology being harnessed to visualise scenes from a
person's dreams or memory.
Writing in the journal Nature, the
scientists, led by Dr Jack Gallant from the University of California at
Berkeley, said: "Our results suggest that it may soon be possible to
reconstruct a picture of a person's visual experience from measurements
of brain activity alone. Imagine a general brain-reading device that
could reconstruct a picture of a person's visual experience at any
moment in time."
It will inevitably also raise fears that a
suspect's brain could be interrogated against their will, raising the
nightmarish possibility of interrogation for "thought crimes". The
researchers say this is currently firmly in the realm of science
fiction because the technique can only be applied to visual images and,
to date, the experiments rely on cumbersome MRI scanning equipment and
extremely powerful magnets. The software decoder itself has to be
adapted to each individual during hours of training while in the
scanner.
However the team have warned about potential privacy
issues in the future when scanning techniques improve. "It is possible
that decoding brain activity could have serious ethical and privacy
implications downstream in, say, the 30 to 50-year time frame," said
Prof Gallant. "[We] believe strongly that no one should be subjected to
any form of brain-reading process involuntarily, covertly, or without
complete informed consent."
The technique relies on functional
magnetic resonance imaging (fMRI), a standard technique that creates
images of brain activity based on changes in blood flow to different
brain regions. The first step is to train the software decoder by
scanning a subject's visual cortex while they view thousands of images
over five hours. This teaches the decoder how that person's brain codes
visual information. The next stage is to take a new set of images and
use the decoder to predict the brain activity it would expect if the
subject was viewing each of them. Finally, the subject views images
from this second set while in the scanner. "We simply look through the
list of predicted activities to see which one is most similar to the
observed activity, and that's our guess," said Gallant.
The
software matched their observed brain activity with the predicted
activity from the decoder. When using a set of 120 images, the software
got it right nine out of 10 times. With 1,000 images, the accuracy was
eight out of 10. For 120 images, if the software were to simply make
random predictions, its success rate would be just 0.8%.
The team
estimate that if they used 1bn images (roughly the number on Google) it
would have a success rate of 20%. With that many images, Gallant said,
the software is close to doing true image reconstruction - working out
what you are seeing from scratch. "There is no reason we shouldn't be
able to solve this problem ... That's what we are working on now."
Gallant
said it might be possible in future to apply the technology to visual
memories or dreams. "Probably the visual hardware is engaged and stuff
from memory is sort of downloaded into your visual hardware and then
replayed," he said. "To the extent that that is true, we should be able
to reconstruct imagery in dreams."
However, tests using moving
images are not possible because MRI scanners are only able to take a
new scan every three to four seconds. Other scientists say the advance
should be welcomed as a major leap in understanding brain function.
"I
think it's a significant advance," said Prof Marcel Just, a
psychologist at Carnegie Mellon University in Pittsburgh. "It's much
more exciting than mind reading and police interrogation ... These
people are finding how the brain codes naturalistic scenes. They
understand what the brain is saying."
"It's definitely an
impressive result. It's pushing still further on how we can make
inferences about mental states from looking at fMRI activity," said
neurologist Dr Steven Laureys at the University of Liège in Belgium. He
said the technique could be useful for understanding the mental state
of a person who is in a coma.
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