Believe it or not, scientists have been using virtual reality setups to study brain activity in lab mice for years. In the past, this has been done by surrounding the mice with flat displays — a tactic that has obvious limitations for simulating a realistic environment. Now, in an attempt to create a more immersive experience, a team at Northwestern University actually developed tiny VR goggles that fit over a mouse’s face… and most of its body. This has allowed them to simulate overhead threats for the first time, and map the mice’s brain activity all the while.

The system, dubbed Miniature Rodent Stereo Illumination VR (or iMRSIV), isn’t strapped onto the mouse’s head like a VR headset for humans. Instead, the goggles are positioned at the front of a treadmill, surrounding the mouse’s entire field of view as it runs in place. “We designed and built a custom holder for the goggles,” said John Issa, the study’s co-first author. “The whole optical display — the screens and the lenses — go all the way around the mouse.”

In their tests, the researchers say the mice appeared to take to the new VR environment more quickly than they did with the past setups. To recreate the presence of overhead threats, like birds swooping in for a meal, the team projected expanding dark spots at the tops of the displays. The way they react to threats like this “is not a learned behavior; it’s an imprinted behavior,” said co-first author Dom Pinke. “It’s wired inside the mouse’s brain.”

With this method, the researchers were able to record both the mice’s outward physical responses, like freezing in place or speeding up, and their neural activity. In the future, they may flip the scenario and let the mice act as predators, to see what goes on as they hunt insects. A paper on the technique was published in the journal Neuron on Friday.