Tiny virtual reality goggles for mice create a convincing world in which scientists can study animal brain activity in a variety of scenarios. This technology brings rodent neuroscience even closer to simulations that are indistinguishable from the real world, researchers say.

For about 20 years, Daniel Dombeck Researchers at Northwestern University in Illinois used rudimentary virtual reality to learn more about how the mouse brain works.

The machines used to observe brain patterns are too large to attach to freely moving mice. Instead, the researchers kept a mouse inside such a machine and placed a screen around the mouse that displayed a virtual reality world when it was placed on a treadmill. The researchers were able to create a virtual world where the mouse could navigate any environment they designed.

“We can run them through a virtual maze and image their brains to see which neurons form memories and remember where they are,” Dombeck says. “[But] What the animal sees is a flat surface, there is no depth perception, and the mouse sees things that are not part of the projection. So there’s a collision of all these cues around us, and we think they’re not fully engaged and immersed in the environment. They are not completely fooled.”

To solve this problem, researchers have now created tiny goggles with a different screen for each eye to cut out everything but the virtual world from the mouse’s field of view and create convincing depth perception. They believe this allows them to perform more accurate experiments because the mice become more convinced of the illusion and behave more naturally.

But designing goggles for mice isn’t as simple as simply miniaturizing technology made for humans. A human’s field of view is just over 200 degrees, while a mouse’s field of view is up to 320 degrees.

This means that the screen inside the goggles needs to be curved and almost surround the eyeball. Although the screen can only display 400 pixels by 400 pixels, Dombeck says that’s enough to be convincing, since mouse vision is much less detailed than human vision.

“The first use of goggles on the first set of mice was quite remarkable,” says Dombeck. “The rats seemed to engage very quickly. When you put the goggles on, it’s pitch black and you can’t see anything, and the virtual rendering turns on. The first rat sat up and said, ‘Oh, what is this?’ It was that kind of feeling. It then started moving pretty naturally, which doesn’t usually happen with flat projection screens.”

Dombeck says the long-term goal is to make mouse technology comparable to what’s seen in mice, with additional devices to trick the senses of smell, hearing, and touch.