Science reports:

Close your eyes and picture yourself running an errand across town. You can probably imagine the turns you’d need to take and the landmarks you’d encounter. This ability to conjure such scenarios in our minds is thought to be crucial to humans’ capacity to plan ahead.

But it may not be uniquely human: Rats also seem to be able to “imagine” moving through mental environments, researchers report today in Science. Rodents trained to navigate within a virtual arena could, in return for a reward, activate the same neural patterns they’d shown while navigating—even when they were standing still. That suggests rodents can voluntarily access mental maps of places they’ve previously visited.

“We know humans carry around inside their heads representations of all kinds of spaces: rooms in your house, your friends’ houses, shops, libraries, neighborhoods,” says Sean Polyn, a psychologist at Vanderbilt University who was not involved in the research. “Just by the simple act of reminiscing, we can place ourselves in these spaces—to think that we’ve got an animal analog of that very human imaginative act is very impressive.”

Researchers think humans’ mental maps are encoded in the hippocampus, a brain region involved in memory. As we move through an environment, cells in this region fire in particular patterns depending on our location. When we later revisit—or simply think about visiting—those locations, the same hippocampal signatures are activated.

Rats also encode spatial information in the hippocampus. But it’s been impossible to establish whether they have a similar capacity for voluntary mental navigation because of the practical challenges of getting a rodent to think about a particular place on cue, says study author Chongxi Lai, who conducted the work while a graduate student and later a postdoc at the Howard Hughes Medical Institute’s Janelia Research Campus. In their new study, Lai, along with Janelia neuroscientist Albert Lee and colleagues, found a way around this problem by developing a brain-machine interface that rewarded rats for navigating their surroundings using only their thoughts. [Continue reading…]