Because humans and mice have similar brain neurons, scientists have studied rodents for generations to better understand the human mind. But researchers have struggled to create realistic virtual environments for mice without the proper technology.
Last week, Northwestern researchers revealed that they had created virtual reality lenses — each of which are 12 millimeters in diameter — that engross mice in virtual surroundings they believe are real. Researchers hope the goggles will expand findings on how mice and human brains process fear, anxiety and post-traumatic stress disorder.
“As crazy as mouse goggles sound, this is exactly the sort of research that eventually trickles down to discoveries that have impacts on human health and disease,” researcher Daniel Dombeck told The Washington Post.
For more than a decade, researchers have tried to embed mice in virtual environments by surrounding them with computer screens, Dombeck said. While some mice have been fooled, others have looked around the laboratory and noticed equipment, tables and people, signaling that the computer displays are fake. Dombeck compared the experience to watching TV in your living room, where chairs and couches remain visible.
Plus, mice can be difficult to trick. Their field of view in each eye is about 160 degrees — roughly 25 degrees more than an average human, according to the researchers.
But virtual reality technology has progressed in the past decade, and people are now using headsets for gaming, job training, health care and exercise. In 2021, Northwestern researchers started creating much smaller equipment for goggles that would fit mice.
The process involved building curved lenses that are each 4 millimeters thick to consume mice’s field of view. Each lens includes a 180-degree camera and a small screen that helps produce realistic colors and lights. Researchers named the goggles “miniature rodent stereo illumination VR.”
Using Unity, a 3D video game application, researchers designed a virtual field that included a small tunnel and a water tube. Researchers also created a small treadmill from foam for the mice to run on. Above the mice’s heads, researchers placed a two-photon microscope to take images of their brains.
Northwestern’s animal care committee approved the researchers’ studies, Dombeck said, and the scientists received about 14 lab mice.
When the researchers started placing the virtual reality goggles on mice, they said, the rodents immediately explored the grassy plain. Every day for about a week, the mice wore the goggles for roughly 40 minutes to adapt to the environment.
Then, while the mice were running through the virtual field, researchers added a black disk in the sky — appearing nearly eight inches from the mice. Some mice froze; others ran away immediately and stopped inside the tunnel. Then, the disk fell toward the mice and “attacked” three times. If the mice had not yet moved, the disk’s motion caused the rodents to scurry to the tunnel.
While the researchers had developed virtual images of owls to charge the mice, they said, the disk was sufficient in prompting a fight-or-flight reaction.
Dombeck, a neurobiology professor, said that mice occasionally emitted fear neurons minutes or hours after their encounters with the disk — a sign they might have been reliving that experience. Domonkos Pinke, another Northwestern researcher, said that in the future, scientists could test how anxiety medicine affects mice’s reactions to stress.
Dombeck has released equipment designs and data for the goggles online in hopes that other researchers will use them. He expects the goggles will lead to scientific discoveries related to fear and PTSD in about a decade.
“Our understanding of the brain is limited by technology,” Dombeck said. “And almost every time something new is invented to study the brain or behavior … we almost always find something new and unexpected.”