Neuroscientists at the University of California, Berkeley, have been able to listen in on people's thoughts, using brain waves to reconstruct the actual words that subjects have been hearing.
"This is huge for patients who have damage to their speech mechanisms because of a stroke or Lou Gehrig's disease and can't speak," says Robert Knight, a professor of psychology and neuroscience.
"If you could eventually reconstruct imagined conversations from brain activity, thousands of people could benefit."
The experiment involved 15 volunteers who were undergoing brain surgery. Up to 256 electrodes were placed on the patients' temporal lobe, recording their brain activity as they heard 5-10 minutes of conversation.
Post-doctoral researcher Brian Pasley then used this data to reconstruct and play back the sounds the patients had heard. The patients were played a single word, and Pasley tested two different models to predict the word based on electrode recordings.
"We are looking at which cortical sites are increasing activity at particular acoustic frequencies, and from that, we map back to the sound," he says.
The better of the two methods was able to reproduce a sound close enough to the original word for Pasley and his fellow researchers to correctly guess the word.
"We think we would be more accurate with an hour of listening and recording and then repeating the word many times," he says.
The team is confident that the method could be used for true electronic telepathy - identifying the words in entirely imagined verbalizations - because studies have indicated that imagining speaking a word activates the same brain regions as when the person actually speaks.
"If you can understand the relationship well enough between the brain recordings and sound, you could either synthesize the actual sound a person is thinking, or just write out the words with a type of interface device," says Pasley.