Breathing Through the Nose May Consolidate Memory

Megan Brooks

November 02, 2018

Breathing through the nose appears to enhance memory consolidation. The findings add to growing evidence that respiration influences perception and cognition, new research suggests.

A recent study demonstrated that nose breathing enhances the encoding and retrieval phases of episodic memory.

"However, the effect of respiration on memory consolidation, the critical process that stabilizes a memory trace after it has initially been obtained, was unknown," Artin Arshamian, PhD, of the Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden, told Medscape Medical News.

The study was published online October 22 in the Journal of Neuroscience.

First Evidence

In the current study, investigators compared the effects of breathing through the nose or mouth on memory consolidation in 24 young men and women aged 19 to 25 years.

The experiment consisted of two separate sessions, each of which included an encoding, a consolidation, and a recognition phase. In the encoding phase, the participants were presented with six familiar odors, such as strawberry, and six unfamiliar odors, such as 1-butanol, one at a time and were asked to remember them.

After the encoding phase, they rested without sleeping for 1 hour, during which they either breathed solely through their nose (nasal consolidation; tape over mouth) or mouth (mouth consolidation; nasal clip). Memory for odors was tested immediately after the consolidation phase.

Breathing through the nose for 1 hour during memory consolidation significantly increased memory recognition, compared to 1 hour of mouth breathing, irrespective of familiarity with odors, the authors note.

"The fact that respiration-type modulates consolidation independent of odor familiarity indicates this effect may not be limited to episodic events involving odors per se, but could generalize to hippocampal-dependent consolidation of items across modalities," write the researchers.

"These results provide the first evidence that respiration directly impacts consolidation of episodic memory and lends further support to the notion that core cognitive functions are modulated by the respiratory cycle," they add.

Mouth Breathing a Sign of Disease?

"Animal studies have shown that respiration through the nose activates memory networks in a different way as compared to the mouth," Arshamian told Medscape Medical News.

"The reason for this is that even when there is no odor, mammalian olfactory sensory neurons detect the mechanical pressure caused by airflow in the nostril and sends this information to the olfafactory bulb that normally codes odor information. The olfactory bulb then sends this information to hippocampus, which is important for memory functions," he added.

For now, "we have taken a step back and want to study how breathing affects the brain generally in humans. I think breathing, no matter if it is through the nose or mouth, affects the neural mechanism underlying not only memory consolidation but a wide range of other processes."

Arshamian said that at this point it's difficult to determine whether the current findings have clinical relevance. It is known, however, that breathing only through the mouth could be a sign of disease, he noted.

"For example, mouth breathing can cause crooked teeth and facial deformities in children. But whether pathological mouth breathing also affects other cognitive functions that are affected by the same mechanisms that we believe are responsible for our results remains to be seen.

"One thing we know is that in many neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease, the olfactory bulbs are negatively affected early on," said Arshamian.

The study was funded by the Swedish Research Council, the Netherlands Organization for Scientific Research, and the Knut and Alice Wallenberg Foundation. The authors have disclosed no relevant financial relationships.

J Neurosci. Published online October 22, 2018. Abstract

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