At Shannon Olsson’s lab at National Centre for Biological Sciences (NCBS), Bengaluru, the emphasis is to get into the mind of insects to study how they perceive various stimuli even though they have brains the size of pinheads. And one way they plan to do this is by building up a virtual reality system that is guided by the study subjects – the insects themselves!
The insect being studied, in this case the apple fly, is tethered to a holder by means of a very fine string so that it cannot move away. The only thing it can do is flutter its wings and “tend” to move in some direction. This insect is placed at the centre of a semi-circular assembly of monitors on which a landscape is shown. The virtual landscape may contain a meadow, trees with various fruit on them, the sky, shrubs etc. In addition, through tiny perforations, wind can be blown on the fly to simulate the breeze. This may come mixed with various volatiles (smells) of fruit, grass etc.
Two cameras observe the reactions of the insect and feed this into the computer that discerns the trajectory, or intended direction of motion, of the insect. Accordingly, the computer adjusts the landscape shown on the monitors. So that if the fly tries to move towards a tree, that portion zooms and the rest shrink, so that it appears to the fly as if it has gone close to the tree. It reacts to this and the cameras feed this back into the computer which once again adjusts the landscape and so it goes.
Using virtual reality to study insects is itself not exactly new: “While true VR for insects does not yet exist, scientists have been tethering (restraining in place) flying insects to study their flight behaviour in front of moving displays for nearly 50 years,” says Shannon Olsson.
How does the fly see?
The question the researchers are trying to understand by building this experiment is – how can an insect differentiate between various stimuli it sees, hears and smells. For instance, what makes the insect drift towards a particular flower or fruit? “Since it is impossible to know when and how an animal receives these cues in the real world, we are creating a virtual world where we can know precisely when the animal receives the colour, shape or smell of a virtual object, and observe its behaviour at that moment as well,” she adds.
Watch: Insect Virtual Reality
This system was built and calibrated over the past two years by Pavan Kumar Kaushik of NCBS for his dissertation work. The graphical interface was built in Germany and inputs for the design came from collaborators in the U.K. “Calibration was performed by directly testing the insect itself. The success of this instrument lies in our chosen system — nearly 50 years of research on the behaviour and ecology of the apple fly have provided us with a large body of knowledge about how they behave in the natural world,” says Pavan Kumar Kaushik. “Our benchmark is therefore how well we can replicate those behaviours in our arena. Essentially, if they respond to virtual objects and a virtual world the way they do in apple orchards, then we have calibrated our parameters properly.”
The team aims to unravel how insects find their food and what stimulates their movements. “Ultimately, we will explore the locations in the brain where this information is being processed, which we have been pursuing with other projects in the lab that measure the neural activity of insect brains,” says Dr Olsson.
