Daydreaming of cheese: new research proves rats have an imagination

Just like humans, other mammals can think about places and objects that aren't right in front of them, according to the findings of a new study.

Rat with Cheese
This rat may well daydream about the place it got this cheese long after the event has past.

As you sit pondering what you'd like for dinner or daydreaming about your favourite place in the world, there's a chance that a rat somewhere nearby is doing the exact same thing.

This is essentially the conclusion of a recent study which found these cheeky rodents possess an imagination just like humans, with the ability to think about objects and places that aren't right in front of them. The findings, published in the journal Science, change what we know about the inner workings of animal brains besides our own.

“The rat can indeed activate the representation of places in the environment without going there,” said Chongxi Lai, postdoctoral researcher at the Howard Hughes Medical Institute (HHMI) and lead author of the study. “Even if his physical body is fixed, his spatial thoughts can go to a very remote location.”

A world of pure imagination

The ability to imagine places away from one's current location is key to remembering past events and contemplating future scenarios. It's a trick which – until now – had only been documented with concrete evidence in the human brain.

But the new study proves that other animals have a form of imagination too, which may help them navigate and process their environment.

The research developed a novel system that combined virtual reality (VR) and a brain-machine interface, to probe the rat’s inner thoughts. This produced a connection between the electrical activity in the rat’s hippocampus and its position in a 360-degree VR arena, allowing the researchers to test whether the rat could activate hippocampal activity to think about a location in the arena without physically going there.

Harnessed on a spherical treadmill, with its movements translated onto the 360-degree screen, the rat essentially had to use its thoughts to navigate to a reward by first thinking about where it needed to go to get it.

City rat
In the wild, the ability to imagine places or objects could give a rat an evolutionary advantage.

In a second, so-called "Jedi task", the rat was entrusted with moving an object to a location in the VR space using thoughts alone. The rat did this by controlling its hippocampal activity, in the same way that a person might imagine taking an empty cup to the coffee machine to fill it with coffee.

Definitive results

The study found the rats could voluntarily generate specific neural activity patterns to recall remote locations distant from their current position. This was done precisely and flexibly, in a way which the researchers say is likely the same in humans.

In addition, the rats were able to hold thoughts of non-physical objects or distant places for many seconds at a time. This behaviour is also very similar to that seen in humans when they relive past events or imagine future scenarios.

“The stunning thing is how rats learn to think about that place, and no other place, for a very long period of time, based on our, perhaps naïve, notion of the attention span of a rat,” said Tim Harris, senior fellow at HHMI's Janelia Research Campus.