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As volunteers used technology similar to a video game to navigate between four locations in a virtual room, researchers monitored changes in blood flow within the brain. ((Maguire and Hassabis/Current Biology))

Scientists have found they can pinpoint the location of a person within a virtual room by reading his mind with a brain imaging device.

"Remarkably … we could tell where they were just by looking at the patterns of activity," said researcher Eleanor Maguire at a news conference prior to the release of the results Thursday in the latest issue of Current Biology.

'It's probably quite … far away from having social and ethical and probably forensic implications.'— Eleanor Maguire, University College London

The researchers scanned the brains of volunteers using a technique called functional magnetic resonance (fMRI), which measures changes in blood flow within the brain, showing which areas are more active.

However, Demis Hassabis, who co-authored the paper with Maguire and several others, said scientists are at least 10 years away from being able to use the technique to determine whether someone is lying about where they have been.

What is fMRI?

Functional magnetic resonance imaging is a technique that shows what parts of the brain are active by detecting changes in blood flow and the amount of oxygen consumed in different areas. Areas that are more active use more oxygen and therefore require more blood flow.

The scanner contains a strong magnet that causes particles inside the core atoms to line up in a certain way, producing a signal that is different for different kinds of atoms. In the case of MRI, the signal from hydrogen atoms in water is measured. The signal varies in different parts of the head, so that some parts appear darker than others.

An additional signal is detected in fMRI. Hemoglobin, the protein that carries oxygen in the blood, produces a slightly different signal when it is bound to oxygen, versus when it is not.

"It's going to require a leap of technology advancement," he said.

Maguire agreed, noting that the technique relies on the co-operation of the subject to train a computer to get familiar with their brain patterns.

"It's quite an involved process that's at a very early stage," she said. "It's probably quite … far away from having social and ethical and probably forensic implications."

The results of the study do open up new avenues for understanding how other memories are coded in the brain, said Maguire, a professor at University College London. In the long term, that could help researchers understand how diseases such as Alzheimer's erode memory and lead to new ways to help patients, she added.

In the study, Maguire and her colleagues asked four male, right-handed volunteers to navigate as quickly as possible 14 times between four positions in a virtual room while they were monitored with an fMRI scanner.

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The hippocampus is known to be the part of the brain involved in spatial memory, as shown here in one of the fMRI scans of a volunteer in the study. ((Maguire and Hassabis/Current Biology))

All subjects showed activity in the same area of the hippocampus, the area of the brain known to encode spatial memory.

Most trials for each location were used to "train" a computer. Based on the training, the computer was able to recognize the pattern for specific locations, allowing the researchers to predict where the volunteer was on the "non-training" runs.

Similar techniques had been used in vision neuroscience before, but not to study memory, Maguire said.

Previously, spatial memory had mostly been studied by looking at just a few neurons at a time in the hippocampi of rats.

Maguire said the fMRI doesn't have very high spatial resolution, so the fact that it could pick out the patterns for different locations suggests that spatial memory is actually encoded over a far larger area than just a few neurons.

The study was funded by the Wellcome Trust, a medical research funding charity.