But this forest is a fiction. It has no smell, sound, or texture. In truth, the cockroach is in a lab, tethered to a wire by a glob of beeswax and resin, its six legs perched atop a large hollow sphere kept afloat by an imperceptible current of air. The unwitting insect is part of an experimental study of virtual reality.
Scientists led by Mikko Vähäsöyrinki, a physicist at the University of Oulu in Finland, have tricked the poor cockroach into thinking it's moving through a forest. And neurobiologists and animal behavior experts are increasingly turning to this trick to perform complex studies that otherwise would be impossible in the wild. "Virtual reality's key benefit is having conditions that enable naturalistic behavior but, for example, are constrained enough to record individual nerve cells while an animal is behaving," Vähäsöyrinki says. That is, the creature's brain activity looks the same as it would if the creature were truly in the wild. But because the creature is not actually moving, scientists can look into its brain and track that activity.
In the cockroach's case, as it looked at a video screen depicting the forest, it moved across a frictionless, hollow foam ball. As the roach ran, it turned the balls, and two image sensors taken from a computer mouse track the ball's rotations. Those sensors were connected to the VR-controlling computer via USB cable, feeding the roach's movements into the computer system so that the screen changes in sync.
Each roach started its journey in the middle of the woods and showed typical roach behavior: fast bursts of activity interspersed with periods of inactivity. Most roaches avoided the trees. The insects tended to fixate on the shadowy darkness surrounding the periphery of the forest, often walking circles around the virtual world like restless goldfish in a bowl.
The simulation wasn't perfect. Occasionally a renegade roach walked though a virtual tree trunk, possibly because it didn't have the feedback from the antennae it would have in an actual forest. But the fact that roaches generally acted the same way in the virtual forest that they would've in a natural environment means that other labs could potentially use the new technology for studying animal behavior.
How to Fool a Roach's Eye
Vähäsöyrinki's tech is just the latest in a long line of virtual reality systems built to study animal behavior and neurology. Most previous setups were designed for rodents but wouldn't be good enough to trick animals with fast vision, including day-active insects such as cockroaches. While a human might enjoy a film shown at 24 frames per second, a blowfly, for instance, perceives 200 frames per second.
So, to fool a fly or a roach into thinking that what it was seeing was real, Vähäsöyrinki sacrificed the green and blue channels of his projector and used them to maximize frame rate at the expense of color. His virtual reality forest, consisting of about 90 trees, had to be displayed in the gray scale, but the team could produce video with a frame rate of up to 360 Hz projected onto a spherical screen with a diameter of 400 mm.
"There are specific behaviors where color information is needed, but if an animal is just walking and something moves by, it uses that image to calculate direction and speed," he says. "Those calculations are done without using color information in most animals, including humans."
In addition to the faster projection rates, Vähäsöyrinki substituted a traditional mirror-based design for a fisheye lens that provided better imaging quality on the spherical surface facing the leashed roaches.
Biology in the Matrix
"Is virtual reality gaining popularity as a research tool?" Bradly Alicea says. "Oh yeah." Alicea is a neurobiologist and computer scientist at Michigan State University who recently co-authored an article about the field. References to virtual reality are suddenly all around us, he says, on the Internet, in video games and on television. As a result, it has become "one of these weird things" that has unexpectedly taken off in the research community. Whereas virtual reality previously only existed in specialized, high-profile labs, now any lab with a few thousand dollars can build its own system for testing animals.
Scientists can answer a variety of questions with virtual reality. At the Arizona Research Laboratories, male moths that were tethered in real life flew through a virtual obstacle course while a research team tempted them with female pheromone olfactory cues. The scientists found that visual information, rather than sex hormones, was the primary driver of moth flight navigation. At Princeton University, mice ran on a spherical treadmill to navigate a virtual maze (custom-built from open-source software from the Quake 2 video-game engine) while scientists tried to see how their brain patterns affected their navigational and spatial awareness. Harvard University scientists have partially immobilized larval zebrafish and induced them to chase small moving spots in virtual reality the same way they would in reality.
All of which brings up an interesting question: Are these lab animals really like the majority of humans in The Matrix, convinced that the virtual reality they see is the real thing? Or are they just playing along?
"I don't think we have a complete answer," says Christopher Harvey, a neurobiologist at Harvard who formerly worked with the Princeton scientists studying mice with virtual reality. Researchers can never be certain, he says, how an animal perceives the world, so they try to create as immersive an environment as possible. For mice—animals that have eyes on the sides of their heads—the key is to create a screen that covers about 270 degrees horizontally and 80 degrees vertically.
Though vision is the most advanced virtual reality system, researchers hope to add olfactory cues to their simulations, or a touch-based stimulus to tickle a mouse's whiskers or a cockroach's antennae. Integrating information from several sensory modalities could be helpful for understanding how an animal uses its senses when operating in the real, and virtual, world. Still, Harvey says, "I think ... it's not clear yet how real the mouse thinks the environment is, or whether the mouse thinks he's playing a video game."
Nevertheless, he says, immersing animals in virtual reality could lead to new insights about not only animal behavior, but also about human health and disease. For example, comparing how a normal mouse and a mouse modeled to have schizophrenia each operate in a maze might pinpoint which areas of the brain are acting abnormally for people suffering from the condition. Performing such experiments in a virtual reality affords researchers a degree of control unimaginable in the real world, where randomness and disorder reign.
"You can control the [virtual] world," Alicea says. "That level of control is very appealing to experimenters."