Pavlovian Experiments on Locusts Provide New Clues on How Smell Works in The Brain

One of the reasons that having a sense of smell is wonderful is that it distinguishes different smells.

How coffee smells can be understood by our brain no matter the season, location or time is a complex question. Our olfactory bulb has a lot of cells that help us make sense of the smells around us.

Researchers turned to an unlikely ally, the Locusts, to break down how coffee smells like coffee, despite other smells and environmental factors getting in the way.

The team from Washington University in St Louis wrote in their new paper that it is still difficult to achieve pattern recognition in artificial chemical systems.

How is this achieved?
The team did a version of the famous Pavlovian conditioning on the American grasshopper. They put an odorant next to the Locusts' antennas and fed them a food reward. The researchers painted the outer mouth parts green to make it easy to see.

After a few rounds of conditioning, the locusts would open their palps and not need food. The first step is recognition, and this response shows that the locusts have done that.

The team checked if the locusts could pick up the same smell in different environments, such as dry or humid, after the locusts wore little sensors that monitored neural activity. The neurons were activated in inconsistent patterns when the palps were open.

The neural responses were variable, according to one of the team.

That seemed to be at odds with what the Locusts were doing.

The researchers used machine learning to figure out what was happening. When an odorant is present, there are a number of 'ON' and 'OFF' neurons that turn on. They don't need to be perfect.

The amount of ON and OFF cells in the brain was the only thing that mattered, with wiggle room to combat any changes for the different conditions that would alter the smells.

While we can't relate these findings directly to humans, studying the responses within a simpler animal model like these insects can help us understand some of the basics of how olfactory systems work.

A model of how a neural system can detect a specific smell amongst a bunch of others has been created.

You can see more about that in the video.
We can't take too much of the study to relate to humans' large olfactory bulbs, but it is a fascinating piece of research. With more study, we can get to the bottom of how our brains can understand the many smells we're surrounded by.

The research has been published.