Scientists Just Solved a Long-Standing Mystery About Our Sense of Smell

Humans are capable of sensing a wide variety of smells, from the first flowers that bloom in spring to the oaky notes of whiskey. Scientists still don't understand every aspect about how our sense of smell works — but now, a team of researchers may have solved a long-standing mystery about our noses and brains.

Millions of olfactory receptor neurons sit at the back of your nose and relay smells to your brain. Each smell we inhale sends tons of odor molecules to the backs of our noses, where all those neurons are waiting. Each neuron only has one kind of receptor on it, so it can only sense certain types of odor molecules. Somehow, all those receptors are equally distributed, allowing us to sense a wide range of smells. But why?

"Over the past decades, neuroscientists have been trying to uncover how nature accomplishes these two goals: selecting one, and only one, type of olfactory receptor for each neuron, while at the same time ensuring that all receptor types are represented in the whole population of neurons," Jianhua Xing, senior investigator on the new study, said in a statement.

What they found: It turns out there's a handy mechanism that makes sure all the smell receptors are evenly distributed around your nose. It's a principle in physics called cooperativity. Cooperativity just means that individual pieces in a system act collectively instead of independently. We see it in all kinds of other biological systems, like the way proteins fold and the way a school of fish swims.

In this case, the researchers created a model that shows how olfactory neurons use cooperativity to function within a system of three layers. The findings line up with previous experimental evidence.

"We are amazed that nature has solved the seemingly daunting engineering process of olfactory receptor expression in such a simple way," Xing said.

The research will help pave the way for new experiments to test how olfactory neurons work.