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A new research reveals that when our nose is blocked due to a cold or allergy, the brain is working hard behind the scene during that time, to make sure that when the sense of smell is recovered, it is as sharp as it used to be.   

According to the new Northwestern Medicine study, in which the nose of the participants was blocked experimentally for a week, the brain exhibited rapid changes in the olfactory regions. This indicated that when the sense of smell is gone, the brain compensated for the interruption and the brain pattern comes down to normal soon after the breathing is restored.

Previous studies have suggested that olfactory system in animals are resistant to perceptual changes due to odor deprivation. This new paper focuses on humans to show how that's possible, the press release stated.

"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 at Northwestern University Feinberg School of Medicine. "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."

For the study, the nostrils of 14 participants were completely blocked for a week, except when they slept at night. The participants stayed in a special low-odor hospital room for the week. It was found that there was an increased activity in the orbital frontal cortex and a decrease of activity in the piriform cortex after the smell deprivation in participants. The two regions affected in the brain, are related to the sense of smell.

"These changes in the brain are instrumental in maintaining the way we smell things even after seven days of no smell," Wu said.

It was found that once the normal breathing was restored, people could perceive odors immediately. Just after a week of deprivation experience, the brain's response to odors had returned to pre-experimental levels, which indicates that deprivation-caused changes are rapidly reversed.

In case of other sensory systems, such as sight, the effects of deprivation are longer.

"It also implies that deprivation has a significant impact on the brain, rather than on the nose itself," Wu said. "More knowledge about how the system reacts to short-term deprivation may provide new insights into how to deal with this problem in a chronic context."

The study is published in the journal Nature Neuroscience.