Breathing. It is just a biological process necessary for ventilation and oxygen to reach cells within our body, correct?
Well, yes, mostly. But breathing, and the way we breathe, directly impacts our neural activity - from memory to fear to our sense of smell, and more.
This knowledge has been around for thousands of years, demonstrated by the importance of meditation in many cultures.
Over 75 years ago, a study (by Edgar Adrian) found that breathing and brain waves in the olfactory system had a close relationship in hedgehogs.
The size and frequency of brain waves have strong links to the airspeed through the nose.
Breathing through the nose vs mouth - Arshamian's experiment
Artin Arshamian, a researcher at the Department of Clinical Neuroscience of the Karolinska Institute, and his team investigated how breathing through the nose or mouth influences memory.
The research team requested male and female participants to sniff and learn to recognize 12 new smells in a “sniffing session”.
For the one hour after the session, one group breathed through their noses, the other breathed through their mouths.
Afterward, each group interacted with the twelve old and new smells and was asked to identify which smells were old and which were new.
Participants who breathed using their noses were able to correctly identify more smells than that of those who used their mouths.
Arshamian hence concluded that memory strength increases when one breathes through the nose during memory consolidation.
A difference in brain activity when breathing in and breathing out?
In 2016, scientists at Northwestern University discovered evidence that breathing influences electrical activity in certain parts of the human brain (mainly concerning emotions and memory)
The results of fear and memory of participants mainly depend on the stage of ventilation one is at, and whether the nose or mouth is breathed through.
Empirical evidence in the study showed that individuals identified fearful faces more quickly and are more likely to remember items when breathing in (instead of breathing out).
However, such observations don't apply if participants breathed through their mouths.
Patients with epilepsy
Northwestern University scientists previously studied seven patients with epilepsy who were scheduled for brain surgery.
Electrodes were implanted into the seven patients' brains, hence acquiring electrophysiological data (to identify seizure cause).
Using the electrophysiological data, scientists found that brain activity, specifically areas of the brain concerning emotions, memory, and smell, was influenced by breathing.
With the same subjects, another study was conducted to test memory.
Object pictures were shown to participants to remember; participants were asked to recall those objects after a set period.
Objects encountered during inhalation were more frequently recalled.
Why stronger memory when inhaling?
Zelano, a professor of neurology at Northwestern University Feinberg School of Medicine, suggested that stronger memory when inhaling provides a survival advantage.
When in a dangerous situation, adrenaline causes the breathing rate to increase rapidly, leading to more time proportionally spent inhaling than exhaling (relative to normal breathing rates).
This possibly aids brain function and increases response rates to danger.