Scientists Use Virtual Reality to Show How Flies Search for Food

(CN) — To understand the uncanny ability flying insects have to quickly discover food, biologists created a virtual reality world for flies, revealing Monday that the insects take their cues from their eyes, sense of smell and airflow.

In a study published in the Proceedings of the National Academy of Sciences, scientists from the National Center for Biological Sciences in Bangalore, India, created a virtual reality program for apple flies. Using a mixture of VR, odors and airflow, the researchers were able to study the flies’ behavior in a naturalistic 3-D setting.

The scientists demonstrated the insects could respond to three dimensional objects in the virtual world and took cues from wind and odors to make decisions.

"With the VR that we built we can begin to get at this question, of what it is that causes them to make certain choices," Shannon Olsson of the national center said.

Pavan Kumar Kaushik, graduate student and chief architect of the virtual world used in the study, explained that the use of VR is nothing new in studying insect behavior, but it often consisted of simplistic objects like stripes that did not reveal everything.

"Stripes are a very neat, simple structure to understand the physiology or mechanism of vision. But they don't help us understand behavior," he said.

In the study, a tethered fly was presented with a panoramic natural outdoor setting with trees, grass and sky. The screen would respond to the beating of the fly's wings, giving it the appearance of movement much like a VR video game. In addition, the scientists added airflow to simulate the wind and puffs of odor.

"What is really interesting about [this] setup is that it attempts to bridge the gap between traditional VR — simple shapes, simple environments — and the natural world of insects," said Vivek Jayaraman, a cognitive neuroscientist from the Janelia Research Campus at the Howard Hughes Medical Institute in the United States.

Watch a video of the "fly" in flight

The researchers chose the apple fly to study due to the amount of research that's already been done with it and its focus solely on apple trees.

 "It's a specialist — it only likes apple trees — so we don't have to worry about whether we're giving it the right stimuli," Olsson said.

The VR world allowed the biologists to accurately study the flies' behavior in a controlled environment, something that would be much harder to do in the real world.

"What they gain is the ability to glean insights into some of the trickier aspects of insect navigation — long-range localization of an odor source, visual algorithms that the insects use to make decisions about whether or not to approach something, and how olfactory, wind and visual cues are combined to get to a food source," Jayaraman said.

The researchers discovered the flies use something called motion parallax to perceive an object's depth across an often complex background. The research team presented the fly with two trees that appeared to be the same size. As the fly moved closer, one tree expanded in size, to represent that it was closer.

The fly moved toward the closer tree, indicating that it could perceive depth from motion and use this insight to find food. As important as visual cues are, the flies also responded to airflow and odors.

"Earlier, there was no way to really isolate these cues. Our VR allows us to do that and show how they use these cues in combination," Olsson said.

After discovering how flies use perspective and motion parallax, the researchers said they will begin testing individual features in the virtual world, such as turning everything upside down, to see just how accurate the flies' senses are.

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