It is possible to read someone’s mind by remotely measuring their brain activity, researchers have shown. The technique can even extract information from subjects that they are not aware of themselves.

So far, it has only been used to identify visual patterns a subject can see or has chosen to focus on. But the researchers speculate the approach might be extended to probe a person’s awareness, focus of attention, memory and movement intention. In the meantime, it could help doctors work out if patients apparently in a coma are actually conscious.

Scientists have already trained monkeys to move a robotic arm with the power of thought and to recreate scenes moving in front of cats by recording information directly from the feline’s neurons (New Scientist print edition, 2 October 1999). But these processes involve implanting electrodes into their brains to hook them up to a computer.

Now Yukiyasu Kamitani, at ATR Computational Neuroscience Laboratories in Kyoto, Japan, and Frank Tong at Princeton University in New Jersey, US, have achieved similar “mind reading” feats remotely using functional MRI scanning.

Between the lines

The pair showed patterns of parallel lines in 1 of 8 orientations to four volunteers. By focussing on brain regions involved in visual perception they were able to recognise which orientation the subjects were observing.

Each line orientation corresponded to a different pattern of brain activity, although the patterns were different in each person. What is more, when two sets of lines were superimposed and the subjects were asked to focus on one set, the researchers could work out which one they were thinking of from the brain images.

In a separate study, also published in Nature Neuroscience, John-Dylan Haynes and Geraint Rees at University College London, UK, showed two patterns in quick succession to 6 volunteers. The first appeared for just 15 milliseconds - too quick to be consciously perceived by the viewer.

But by viewing fMRI images of the brain, the researchers were able to say which image had been flashed in front of the subjects. The information was perceived in the brain even if the volunteers were not consciously aware of it.

The study probed the part of the visual cortex that detects a visual stimulus, but does not perceive it. “It encodes what we don’t see,” Haynes says. He thinks that, further along the visual pathway, brain regions consciously take note that there has been a stimulus. But this does not happen for the “invisible” stimulus.

Consciousness kicks in

By understanding the perception pathway and working out the point at which consciousness kicks in, patient consciousness could be diagnosed. This would mean the setup could be used as a “consciousness-meter,” says Haynes; “a device that allows us to assess whether a patient is consciously perceiving his or her outside environment.”

Yang Dan, a neurobiologist at the University of California in Berkeley, agrees this would be possible. But she cautions that there is little agreement over what consciousness actually is.

More subtle forms of mind-reading such as working out intentions or beliefs are much more speculative, she argues. Even if such subtle information could be gleaned from brain scans both studies suggest the patterns are unique to individuals.

And using the technique as an alternative to the polygraph would be very risky, says Dan. “The relationship between brain patterns and lies may be very loose.”

Journal reference: Nature Neuroscience (DOI: 10.1038/nn1445 and 10.1038/nn1444)