Scientists Can See What's On Your Mind

(March 11) -- Mind-reading devices are still a thing of science fiction, but scientists can now peer into the brain and pinpoint complex memories.

In the latest issue of the journal Current Biology, researchers at University College London report using a brain scanner to effectively figure out what different people were thinking. "Given a set of memories, we could tell just from the patterns of activity in the hippocampus which memory a person was recalling," says study co-author Eleanor Maguire.

Previously, Maguire and her colleagues used functional magnetic resonance imaging (fMRI) to guess where a person imagined themselves to be within a virtual environment. But Maguire says that these spatial memories are easier to decode than episodic ones -- the rich, detailed recollections of our everyday experiences.

In their new study, the group describes how they made the leap to deeper thoughts. Ten subjects repeatedly viewed three different video clips of everyday experiences. Each clip was just seven seconds long and involved a fairly mundane action -- a woman on an urban sidewalk drinking from a cup, then tossing it in a trash bin, for example. But the subjects viewed each one 15 times, then practiced remembering the videos, effectively writing them into their brains.

Next, during the scanning phase, the fMRI machine monitored activity as the subjects recalled each of the clips seven different times. In one phase, they were cued to recall a specific one of the scenes, and in another, they chose on their own, and then typed on a small keyboard which video they'd been thinking of. "By having the same movies for each person, we ensured that everybody was recalling the same memories," Maguire explains.

The scientists trained an algorithm to recognize patterns in brain activity associated with each of the memories so that when the subjects chose which video to recall on their own, the scientists were able to gauge the algorithm's success. "We were able to work out how good the algorithm is at predicting which memory was being recalled at a certain point in the experiment," Maguire says.

The goal of the work isn't to extract memories, but to figure out how they are maintained and managed within the brain, and even what happens to them over time. Maguire says that this particular study highlights the role of certain brain structures in recalling and storing episodic memories. "The hippocampus is contributing something very special," she says.

But now that they can look at individual memories, it may be possible to study how the brain manages memories over time. "We can track them and see what happens to them under a range of different circumstances," Maguire says. "Do they change? Do different brain areas become involved?"

One thing they cannot do, Maguire says, is read random minds. For this technique to work, they need to interact with the subjects beforehand and prep the system. "It's not simply a matter of taking somebody, putting them in the brain scanner, and being immediately able to predict what they're thinking."

So, we are all still safe from mind-reading -- for the time being, at least.