There are some things we just assume are true. For instance, I take for granted that heat rises. I expect rain to make things wet. And yes, I’d always thought our nostrils both smelled the same smell (same nose, same environment, right?).
Wrong, apparently. Recent research published in Current Biology found that we know almost nothing about noses ― “Despite extensive work on odour responses in the olfactory system, relatively little is known about how information from the two nostrils is integrated and differentiated in the human olfactory system,” they say.
Their study revealed that each nostril “maintains distinct representations of odour input from each nostril through temporal segregation” ― in other words, different nostrils smell different things. Like, all the time.
I know! The study was done on ten epilepsy patients, and involved researchers puffing scents and a control through one, and then both, of participants’ nostrils.
Participants were then asked the detect the smell and explain which nostril they used to detect it ― meanwhile, electrodes detected their brain’s activity. They focused in particular on the part of the brain that recognises smell.
And they found that when participants smelled with both nostrils, there were two burst of activity in the brain ― milliseconds apart ― that seemed to correspond to each nostril’s scent info.
“Odour information arising from the two nostrils is temporally segregated in the human piriform cortex,” the scientists found. In this way, the scent-recognising part of your brain can “maintain distinct representations of odour identity for each nostril” ― or, it could help it to work out which smell came from which side.
The researchers could only really speculate. “Differences in odour concentration across the two nostrils help rodents localise an odour source and can bias motion perception in humans toward the nostril with the higher concentration odourant,” they found.
“Such findings strongly imply that the olfactory system is equipped to both integrate and segregate odour information arising from each side of the nasal cavity,” they added, suggesting the nostril lag could both help us to locate the source of smells and take in odours as a whole.
But until further research is undertaken, well, who nose?