Document type: news published in Science
Author: Catherine Offord
Preview: Virtual reality study suggests that rodents, like humans, are capable of mental navigation.
[...] Rats [...] 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. [...] 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 [...]. In their new study, Chongxi Lai, [...] 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.
First, the team designed a miniature virtual reality arena and displayed it on a screen surrounding a spherical treadmill, a bit like the trackball of a computer mouse. Rats could scamper through this arena by running on the treadmill, and if the animals navigated to particular objects in the arena, they'd receive a sugary reward. Throughout the rats' wanderings, the team measured brain activity in the animals' hippocampus.
Next, Lai and colleagues disconnected the treadmill so that the rats could still see the virtual reality arena, but their running had no impact. Instead, the team hooked up the display to real-time readings of the rats' brain activity. By reproducing the brain activity they'd shown during the previous training sessions, the rats could navigate to reward locations using just their thoughts. Some scampered futilely on the treadmill as they did so, but others remained still.
In another version of the setup, the rats' brain activity was used to control the location of a box on the screen rather than the animals' own movement in the arena. (The researchers call this the "Jedi" experiment, after the telekinetic powers in Star Wars.) Once again, the team found that the rats could reactivate neural patterns from the training sessions to steer the box toward a goal and earn a reward. [...]
