Still a Mystery: Sense of Smell
Of all our senses, the least understood is smell. The brain region responsible for it is called the olfactory bulb and it’s way more complex system than our sight. Our noses hold at least a million odor receptors comprised of at least 400 types. The gene family behind odor receptors is among the human genome’s largest, allowing us to detect up to 80 trillion odors.
We have this amazing ability because odor chemicals come in different physical shapes to interact uniquely with many receptors. Consider a cat while blindfolded. Touching a cat’s head versus its claws conveys very different shapes. So, depending on the “piece” of the molecule’s shape that a receptor binds, different receptors can interact with the same odor chemical and send independent signals to the brain.
To make it even more complicated, a chemical’s structure doesn’t predict its odor or smell. Vastly different chemicals can trigger the same smell.
Also, our sense of smell is very subjective. For some, the smell of fried liver and onions is divine but to me it smells like burning tires. And to make it even more complex, what we smell is a response to not one but a mix of chemicals.
We’re using AI to learn how our olfactory receptors recognize odor chemicals. We know that two similar molecules can be perceived as different smells. Maybe one day we’ll understand how fresh-brewed coffee can have such an effect on java lovers.
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The biology of smell is a mystery — AI is helping to solve it
The smell in the laboratory was new. It was, in the language of the business, tenacious: for more than a week, the odour clung to the paper on which it had been blotted. To researcher Alex Wiltschko, it was the smell of summertime in Texas: watermelon, but more precisely, the boundary where the red flesh transitions into white rind. “It was a molecule that nobody had ever seen before,” says Wiltschko, who runs a company called Osmo, based in Cambridge, Massachusetts. His team created the compound, called 533, as part of its mission to understand and digitize smell. His goal — to develop a system that can detect, predict or create odours — is a tall order, as molecule 533 shows.
The biology of smell is a mystery — AI is helping to solve it
Scientists are beginning to crack the fiendishly complex code that helps us to sense odours.