We know that the nose is the tool we primarily rely on to take in smells, but the process our nose undergoes from there, in conjunction with our brains, is less understood. According to new research detailed by The New York Times, once an odor hits the receptors in our nose, it spreads those signals through a vast, highly specific network of spatial patterns leading up to our brain, a major shift from the long-held belief that this system was essentially random.
Vision, hearing, and touch all follow neat, organized maps in the brain. You touch something, and then neighboring cells process neighboring inputs. Smell, on the other hand, seemed the most chaotic department in an otherwise organized company. It would take in those signals and then spread them to hundreds of thousands of receptors scattered around the brain, with no clear rhyme or reason.
That assumption is now being challenged.
Scientists Finally Mapped Out How Our Brains Decode Smells
In two new studies published in Cell, you can find here and here, researchers mapped the olfactory systems of mice with unprecedented detail. Using genetic sequencing and advanced imaging, they discovered that each type of odor receptor, of which there are over 1000 in mice, occupies a consistent, predictable place in the nose. That spatial layout is then mirrored in the olfactory bulb, a.k.a. the brain region that processes smell.
This means that sent signals aren’t randomly scattered about. On the contrary, it’s actually quite well organized; we just couldn’t see it before now.
Each receptor is tuned to a specific set of odor molecules, and each neuron carries only one type. What the researchers found is that where a neuron sits in the nose helps determine which receptor it relates to in the brain. The tissue connecting the two essentially guides neurons into their proper positions, ultimately forming a structured map that the brain can read and follow more easily.
Why this map even exists is anyone’s guess. The researchers have some theories, like how it could be grouping similar chemical smells together for convenience, or maybe it’s more complex and it’s organizing odors by meaning, separating delightful smells like freshly baked bread or perfume from foul smells that may suggest danger, like decay.
While they still have details like that to work out, one thing that is abundantly clear right now is that this discovery fundamentally changes everything we know about how smell works. When you smell a delicious meal, your brain isn’t shotgun blasting across your brain. If using a very specific set of roads to send it to a very specific part of your brain, and knowing that may help us one day fully understand how and even why we interpret scents the way we do.
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