It turns out that memory is strengthened by nose breathing

A researcher at the Karolinska Institute in Sweden, who was conducting a study on how breathing affects the activities of the brain, in particular on the memory, conducted an experiment in which researchers at the Karolinska Institute in Sweden "strengthened smell memories by performing nasal breathing" The results are announced.

Respiration modulates olfactory memory consolidation in humans | Journal of Neuroscience
http://www.jneurosci.org/content/early/2018/10/22/JNEUROSCI.3360-17.2018

Breathing through the nose aids memory storage - ScienceDaily
https://www.sciencedaily.com/releases/2018/10/181022141509.htm

When smelling something, the molecule that forms the odor binds to the olfactory receptor located in the back of the nose, and the electrical signal of the receptor reaches the brain tissue called the " olfactory bulb " through the olfactory receptive nerve . And it is thought that smell is recognized by sending the olfactory information processed by the olfactory bulb based on the signal to the cerebrum.

This olfactory bulb has a circuit also with the hippocampus , which is a brain tissue related to memory, and it has been clear from previous studies that smell and memory are closely related. From this, Artin Arshamian who studies clinical neuroscience at the Karolinska Institute advocated the hypothesis that "The memories on odor may be enhanced by nose breathing rather than mouth breathing" and compared experiments.

The research team led by Mr. Arshamian made 12 kinds of different smells to the subjects. After that, after having made mouth respiration or nose breathing for 1 hour, it smells "12 kinds of smells first smelled" and "12 kinds of smells completely different", and smells smelled before Investigate whether or not. As a result, I found that the group who had been taking nasal breath for 1 hour remembered the smell more strongly than the group that had mouth breathing.

The memory process can be broadly divided into three stages of " encoding ", " fixation " and " recollection ". Arshamian argues from this experimental result that "Respiration affects immobilization of memory" was shown.

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However, it is said that the mechanism of how nasal respiration specifically influences immobilization of memory has not been elucidated. According to Arshamian, until now, it was impossible to measure the activity of the olfactory bulb unless the electrode was directly inserted in the brain, but as of 2018, there are established methods that can be measured without inserting electrodes is. "The next goal is to find out what actually happens in the brain during breathing and how it relates to the formation of memories," Arshamian said.