Nose Breathing May Benefit the Brain
Lately more experiments have looked at how breathing influences our cognition, especially memory. The Journal of Neuroscience published a study in October, 2018 that looked at the relationship between our memory and our method of breathing—through the nose or through the mouth.
Many studies show that as rodents sniff anything including odorless air it starts activity in the brain by stimulating neurons in the olfactory bulb. This in turn signals the hippocampus. This is a region in the brain which is involved in creating and storing memories. The researchers experimented to see if a similar thing happens to humans that breathe through their mouths instead of their noses.
The study looked at 24 healthy men and women. They breathed 12 distinct scents and memorized them. They then sat for an hour with their nose clipped shut to force mouth breathing during that hour. They were then exposed to the 12 scents and other scents also. They were asked if each scent had been one that they had sniffed before. This was repeated with their mouths taped shut for that hour to prevent mouth breathing.
The volunteers had better recognition of the scents when they breathed through the nose during the hour after they initially smelled the scents. When they breathed through their mouths for the hour, they had worse recall and more incorrect answers. The result was that nose breathing made memory consolidation better. It was assumed that breathing through the mouth bypassed the olfactory bulb and did not start the same neuronal response.
Of course, memory problems are a symptom found in obstructive sleep apnea and so is breathing through the mouth. Since we were designed to breath through the nose, there may be other similar neuronal pathways that are initiated by nose breathing. Maybe taping the mouth shut the night before a big exam or presentation would help! Nasal breathing has many good effects—too many to go into in this article. But people who have been treated for sleep apnea do have improvement in their memory.