It reads like science fiction, but Christian Hölscher and collaborators in Hanspeter Mallot's team at Tübingen University have designed an ingenious virtual reality machine for rodents(p. 561). Rats happily run along on a big ball, deftly navigating through a virtual reality environment projected onto a screen surrounding the animal. But the team weren't designing a rat amusement arcade - their aim was to provide navigation researchers with a perfectly controllable environment to investigate how rodents process navigational information. Mallot's team has succeeded admirably in achieving that goal.
Knowing that humans and primates have no problems learning in virtual environments, Hölscher and the team took on the challenge of designing a virtual reality environment for rats. If they could pull it off, the team knew that this would provide significant benefits for future spatial navigation research. Real life is just too complicated; field researchers don't know which sights or smells rats use to find their way around their large home ranges. A virtual environment would give researchers complete control over all the factors that may influence how free-roaming rodents navigate.
The team designed a virtual reality machine based loosely on a smaller model built for insects. The idea was to place a rat on top of a large air-cushioned polystyrene ball surrounded by a 360° screen. As the rat wanders along, wearing a little harness to prevent it from jumping down, the ball rotates. A computer detects the ball's movements and constantly calculates new images that are projected onto the screen, so that the rats'virtual environment is updated in real time. The team were anxious to see how the rats would respond to this new virtual world. Hölscher admits that`it was a bit of a gamble. This had never been done before and we didn't know how rats would cope.' The team were surprised to find that the rats were quite happy to stroll along on top of the ball. `They didn't need any training to accept the virtual environment and even seemed to enjoy themselves'Hölscher recalls, adding `They ran for miles on this high-tech version of a hamster wheel.'
But were the rats really able to see the virtual landscape? The team needed to show that the rats' movements on the ball were visually guided. They decided to lure the rats with a tasty treat to see if the rodents could learn to navigate around the virtual environment in a target-oriented manner. They rigged the rat harness with a little tube that squirted sugar water into the rats' mouths whenever the animals successfully navigated to specific landmarks, virtual cylinders suspended from the virtual ceiling. Plotting the rats' trajectories as the animals sauntered around the virtual world, the team was soon convinced that the rats became quicker at locating new landmarks and were running shorter distances to reach the landmarks over time. The rats were not wandering aimlessly but were clearly navigating to the cylinders for their sugary reward.
Hölscher is excited about the unmitigated success of the rodent virtual reality machine and the new research opportunities that can now be explored. He enthuses `This may represent a small revolution in navigational research.'