Brain stimulation guides people through an invisible maze

You’re stuck in a maze. You can’t see the walls, or the floor. All you have to navigate is a device on your head stimulating your brain to tell you which way to go.

In an experiment at the University of Washington in Seattle, participants solved a maze puzzle guided only by transcranial magnetic stimulation (TMS). The findings suggest that this type of brain prompt could be used to augment virtual reality experiences or help give people who are blind “visual” information about their surroundings.

Darby Losey and his colleagues created a virtual maze in the style of a simple 2D video game through which people had to guide an avatar. But they couldn’t actually see the maze – instead, they faced a blank screen. At regular intervals, a question box would pop up asking if they would like to move forward or make a turn.

How did they know whether to keep going or change course? Each time their avatar got too close to a wall, they were given a dose of TMS to the primary visual cortex at the back of their brain.

TMS produces small electric currents that can at certain intensities induce the perception of a flash of light called a phosphene. No light actually enters the eye, but the brain still “sees” it. Phosphenes can also occur if you put pressure on your eyeballs when rubbing your eyes.

To successfully escape from the maze, all the participants had to do was carry on walking until they experienced a flash of light. When that happened, they knew they had reached a wall and had to turn.

Participants successfully completed an average of about 92 per cent of the steps to get through a variety of different mazes. In contrast, a control group provided with a fake TMS machine that gave them no stimulation completed just 15 per cent, suggesting that TMS was helpful in guiding people and they weren’t just guessing.

“A lot of research has been done trying to extract information from the brain,” says Losey. He is more interested in using TMS to put information into it.

Phosphenes are not only experienced by sighted people, but also those who are blind. This means that similar systems could one day help to give people who are blind more information about their surroundings by providing “visual” clues using brain stimulation.

“This is a very promising initial study,” says Eric Thomson at Duke University in Durham, North Carolina. The set-up is currently basic, given that the participants only had a simple binary choice to move forward or turn. “But it has the potential to be expanded to convey more information,” says Thomson.

Losey’s ambition is to eventually augment virtual reality in a way that can’t be achieved with a pair of goggles alone. “Traditionally virtual reality is done through goggles and headsets, but really it’s your brain that creates your reality. We want to go directly to the brain,” he says.

He wants to find ways to use brain stimulation to communicate more complex experiences than just a flash of light. “The ultimate goal is to convey other forms of information. That could be something abstract, like the colour blue, or even an emotion.”

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