A mind-reading experiment by British scientists has shown that a person’s thoughts can be decoded from a brain scan, offering new insights into the formation of memory.

Researchers can tell where a person is “standing” in a virtual reality room purely by looking at patterns of activity in the brain, the study at University College London has found.

The findings indicate that it is possible to read at least a small part of people’s minds using functional magnetic resonance imaging (fMRI), and open a new window on the way the brain learns and constructs memories.

“With this kind of research, we are approaching the realm of mind-reading,” said Eleanor Maguire, a leader of the study.

Her colleague Demis Hassabis said: “You can predict where someone is standing by reading the patterns in their brain activity. You can track what is purely an internal thought.”

While the research could shed light on disorders that involve changes to brain structure or memory loss, such as amnesia, dementia and stroke, it does not suggest that MRI mind-reading could soon be used to detect lies or reveal thoughts without their consent.

The procedure works only with the co-operation of its subjects, who must repeat the virtual reality game again and again in the scanner to calibrate the computer algorithm that matches brain activity to particular thoughts. It can also detect only very simple thoughts.

“We can rest easy in terms of issues surrounding mind-reading,” Professor Maguire said. “While technically we were able to predict somebody’s spatial memory from their brain activity, there was nothing intrusive about what we did.

“This analysis technique requires the person to be co-operative with us, to train the algorithm we use on many instances of a particular memory. It’s not that we can put somebody in a brain scanner and we can suddenly read their thoughts. It’s quite an involved process.

“Its far away from having social, ethical and forensic implications. In the future it will be interesting to see how these techniques develop.”

Dr Hassabis said: “It would be impossible to use the technique to detect whether somebody is lying or not, because they could easily fool the system just by lying during the training sessions. The current techniques are a long way away from doing those kinds of things, though in the future they may become more possible. It might be useful to start having those kinds of ethical discussions in the near future in preparation.”

In the study, published in the journal Current Biology, volunteers were asked to navigate around four places in a virtual reality room. At the same time, the fMRI scanner recorded activity in the hippocampus, the part of the brain that deals with navigation, many memories and imagining the future.

Previous research led by Professor Maguire has found that a part of the hippocampus is enlarged in London taxi drivers, reflecting the memories for locations they form when learning “the knowledge”.

As the subjects started to form memories for each of the four spots, a computer algorithm gradually became capable of identifying them according to patterns of brain activity.

This suggests that the hippocampus lays down memories in a structured and predictable fashion, which challenges standard thinking. Studies with rats had suggested that there is no structure to the way the hippocampus forms and stores memories.

Professor Maguire said: “fMRI scanners enable us to see the bigger picture of what is happening in people's brains. By looking at activity over tens of thousands of neurons, we can see that there must be a functional structure — a pattern — to how these memories are encoded. Otherwise, our experiment simply would not have been possible to do.”

Dr Hassabis said: “Understanding how we as humans record our memories is critical to helping us learn how information is processed in the hippocampus and how our memories are eroded by diseases such as Alzheimer’s.

“It’s also a small step towards the idea of mind reading, because just by looking at neural activity, we are able to say what someone is thinking.”

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