Researchers have just discovered that we smell odors in stereo…
Mathilde Fontez, editor-in-chief of the magazine Epsiloon, tells us about the work of a team of American researchers, who have reconstructed the path of odors in our brain, and who found a difference between our two nostrils.
franceinfo: What does this recent research on the path of odors demonstrate?
Mathilde Fontez: We have two nostrils, but is that an advantage? Is it just the same detector, picking up the same thing? Or do these two channels allow us to smell morning coffee and the toasted smell of toast more delicately?
These are all questions that researchers at the University of Pennsylvania in the United States asked themselves. And to answer it, they had the chance to carry out their investigation directly into the brain, the human brain. A rare opportunity.
They used electrodes to track the activation of brain areas?
Yes, and on awake patients. These are epileptic patients who underwent surgery to identify the areas of the brain responsible for seizures. The American researchers were able to add their experimental protocol to the surgical protocol, and present different odors to patients, sometimes to a single nostril, sometimes to both, while precisely following the activity of the brain, in particular an area, where the information is processed. olfactory: the piriform cortex.
And what did they see?
They saw two neural pathways, two pathways, one for each nostril. The brain is capable of differentiating the arrival times of odors, from one nostril to the other: when the odor was transmitted to one side only, this side reacted first in the brain, the reaction of the opposite side was a little offbeat.
The brain also seems to reinforce the smell when it hits both nostrils: it recognizes the smell more quickly, as if there was some kind of synergy. In short, we are indeed capable of coding into which nostril an odor enters, we perceive – unconsciously – the difference.
Does it allow us to smell where the smells come from?
In any case, it refines our perception, say the researchers. But we remain very far from the performances of certain animals. Like rats: they are able to navigate based on the difference in odor concentration in their two nostrils. Or the shark too which senses the time difference between the two nostrils to identify a target and attack.
It appears that the farther apart the animals have nostrils, the more efficient this system is – this could be the evolutionary secret to the hammerhead shark’s efficiency. None of that at home, but all the same, we feel in stereo.