'What's on your mind?'
2008-03-06 21:17
Paris - Venturing into the preserve of science fiction and stage magicians, scientists in the United States said on Wednesday that they had made extraordinary progress towards reading the brain.
The researchers said they had been able to decode signals in a key part of the brain to identify images seen by a volunteer, according to their study, published by the British journal Nature.
The tool used by the neuroscientists from the University of California at Berkeley is functional magnetic resonance imaging (fMRI), a non-invasive scanner that detects minute flows of blood within the brain, thus highlighting which cerebral areas are triggered by light, sound and touch.
Their zone of interest was the visual cortex - a frontal part of the brain that reconstitutes images sent by the retina.
Scanned set of pictures
Using two of their number as volunteers, the team built a computational model based on telltale blood-flow patterns in three key areas of the visual cortex.
The signatures were derived from 1 750 images of objects, such as horses, trees, buildings and flowers that were flashed in front of the subjects.
Using this model, the programme then scanned a new set of 120 brand new pictures to predict what kind of fMRI patterns these would make in the visual cortex.
After that, the volunteers themselves looked at the 120 new pictures while being scanned. The computer then matched the measured brain activity against the predicted brain activity, and picked an image that it believed was the closest match.
They notched up a 92% success rate with one volunteer, and accuracy was 72% in the other. The probability of this happening on the basis of chance, that is the computer picking the right image out of the 120, is only 0.8%.
The lead author, Jack Gallant, likened the task to that of a magician who asks a member of the audience to pick a card from a pack, and then figures out which one it was.
The ambitious experiment was taken a stage further, expanding the set of novel images from 120 to 1 000. The first volunteer took this test and accuracy declined but only slightly, from 92% to 82%.
Could diagnose areas
The researchers say the device cannot "read minds", the common term for unscrambling thoughts. It cannot even reconstruct an image, only identify an image that was taken from a known set.
Doctors could use the technique to diagnose brain areas damaged by a stroke or dementia, determine the outcome of drug treatment or stem-cell therapy and fling open a door into the strange world of dreams.
And, according to one futuristic scenario, paraplegic patients, by thinking of a series of images whose fMRI patterns are recognised by computer, may one day be able to operate machines by remote control.
- SAPA