How the Human Nose Rebounds from Periods of Stuffiness
Everyone once in a while, we all succumb to the dreaded stuffy nose. It is a terrible thing, causing dry mouths in the morning and loud sniffles and discomfort during the day. Another awful thing it causes is a noticeable decrease in our perception of odors, (not such a bad thing when passing by a skunk or dirty public restroom). However, for the human body, the olfactory sense is extremely important, evolving over time to alert the individual of impending danger, or more importantly, if there is food nearby. That is why after the stuffiness has gone, our sense of smell returns lightning-fast and as sharp as ever.
This was found out through laboratory experiments at the Northwestern University Feinberg School of Medicine. Human noses were experimentally plugged up for one week, and the scientists observed rapid changes in the olfactory regions of the brain. This suggests the brain is compensating for the loss of smell. Shortly after the nose is unplugged, the brain activity returns to normal
"You need ongoing sensory input in order for your brain to update smell information," said Keng Nei Wu, the lead author of the paper and a graduate student in neuroscience. "When your nostrils are blocked up, your brain tries to adjust to the lack of information so the system doesn't break down. The brain compensates for the lack of information so when you get your sense of smell back, it will be in good working order."
The experiment was conducted with four individuals in a special low-odor hospital room. Humanely, their noses were unplugged at night so they could sleep soundly.
The regions of the brain affected were the orbital frontal cortex which had an increase in activity. The decrease in activity occurred in the piriform cortex, a region related to the sense of smell. The ability to smell after not being able to smell for an extended period was immediate, with little delay in strength or accuracy.
Compare this with deprivation of other senses. If one was trapped in a lightless room for hours and then exposed into the light, the eyes would struggle immensely to adjust, and may not ever be able to return to its pre-deprivation state.
How could this be, since humans rely on their sense of sight just as much if not more than sense of smell? One reason, speculates Wu, is that smell deprivation is much more common due to viral infections and allergies. We have evolved to overcome them rapidly and move on with our lives.
This study has been published in the journal Nature Neuroscience
Stuffy Nose image via Shutterstock