Smelly Locusts

By Alice Orszulok

Scientists train locusts to recognise odours to better understand our own sense of smell.

When you walk outside, what is the first thing you notice? The trees around you? The birds singing from the trees’ branches? The rough gravel beneath your feet?

Of all our five senses, our sense of smell is potentially the most powerful. It is strongly associated with our memory and is the only one of our senses that is directly hardwired into our brains.

Smell is really just a reaction to the chemicals around you. For instance, if you smell something good such as food, you want to eat it, but if you smell something bad such as dog droppings, you want to move away. However, there is often more than one smell in our surroundings, so how does our brain process all these different odours at the same time?

One scientist wanted to find out just that, so decided to use locusts—which have a simple sensory system—to study what happens to the brain when it is stimulated by a smell.

Researchers led by Barani Raman from Washington University in St. Louis administered puffs of a certain smell to the locusts, and a few seconds later would give the locusts a piece of grass as a reward. This is a form of Pavlovian conditioning. As with Pavlov’s dog, which salivated when it heard a bell ring, the locusts would anticipate the reward when after the odour was delivered. Instead of salivating, they open their palps (finger-like projections close to their mouths) when they predict the piece of grass. Even when the researchers tried to distract the locusts with other smells at the same time, the locusts would still recognise the first odour and would respond within half a second.

“We were expecting this result, but the speed with which it was done was surprising,” said Raman in a press release. “It took only a few hundred milliseconds for the locust’s brain to begin tracking a novel odour introduced in its surrounding. The locusts are processing chemical cues in an extremely rapid fashion.”

According to Raman, this test is the first of many to further understand the principles of how our olfactory system works. How locusts perceive odours could be very different to how we do, especially since our bodies and sensory systems are much more complex.

Source [Washington University]

Keyword [Olfactory]

The sense of smell, called olfaction, involves the detection and perception of chemicals in the air. The olfactory system in humans is very complex and includes structures in the nose and the brain.