2023-08-18 13:48:00
Vanilla is the favorite smell of the French. However, if the latter is unanimous, olfactory tastes can vary from one individual to another. But where do our olfactory preferences? A recent study, conducted by Washington University in St Louis (USA) sought to understand this. The results were published in the journal Nature Communications on August 5.
A study conducted on locusts
For this study, the researchers observed locusts. They chose these particular insects because their olfactory system is vital for survival and guides their behavior. The scientists therefore observed how their brain reacted to various smells and the behavior that manifested in response to them. They have used 22 different smells in order to understand which odorants locusts found appetizing or not.
The locusts’ favorite smells were those resembling grass (hexanol) and banana (isoamyl acetate). On the contrary, the least loved were those who smelled of almond (benzaldehyde) and citrus fruits (citral). “We found that locusts responded to some smells and not others, then we split them into a single behavioral dimension“, explain the researchers.
So, to understand what made the smells pleasant or unpleasant for the locusts, the researchers starved them and then exposed to each of them for 4 seconds. In the meantime, insect neural responses were measured. These contained information that could predict their behavior.
Appealing scents are associated with a food reward
Some locusts showed no response to exposed odors. So the researchers wanted to see if they could train them to react to these smells. For this, they presented to each cricket a different odorant by then giving it a piece of grass as a reward. They then discovered that locusts associated odors with a food reward.
“With the ON training approach, we found that the locusts opened their palps immediately after the appearance of the smellremained open during odor presentation, then closed after odor ceased,” the study authors explain. “In contrast, the OFF training approach allowed locusts to open their palpi much more slowly, reaching the maximum response after the smell stops.” Thus, when the reward was given mattered. When given 4 seconds after smelling the odor, the insects did not assimilate it as a reward. The result was the same with the odors judged to be the most attractive.
This experiment therefore shows that the preference for certain smells can be learned. “All information received by our sensory apparatus, and its relevance to us, must be represented by electrical activity in the brain. It seems that sorting information in this way happens as soon as sensory signals enter the brain“, conclude the researchers.
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