The way we breathe affects our memory in mysterious ways.
Recently, neuroscientists have been scrutinizing the link between smell and memory.
Some have suggested that a damaged sense of smell can predict dementia, and others have zoomed in on why that may be.
Along the way to unraveling the Proustian mysteries of smells and memory, scientists have picked up several clues.
The amygdala, which is a small brain region that processes sensory information, is close to the memory-storing hippocampus.
Also, newer research shows that people with a good spatial memory may be better at identifying smells. Information related to time and space is present in the anterior olfactory nucleus, studies have shown. This is a brain area that is involved in the development of Alzheimer's.
New research now adds breathing into the mix. A study carried out by scientists at the Karolinska Institutet in Stockholm, Sweden, finds that breathing through the nose, rather than the mouth, improves olfactory memory.
Artin Arshamian, a researcher at the Department of Clinical Neuroscience with the Karolinska Institutet, is the first author of the paper.
Breathing through the nose may aid memory
Arshamian and team asked male and female participants to learn 12 new smells on two occasions. After each "sniffing session," they asked the participants to breathe either through their noses or through their mouths for 1 hour.
When the hour was up, the participants smelled the old 12 scents along with the dozen new ones. The participants then decided which smells were old and which were new.
Overall, when the people breathed through their noses, they memorized the smells better than when they breathed through their mouths.
"Our study shows that we remember smells better if we breathe through the nose when the memory is being consolidated — the process that takes place between learning and memory retrieval [...] This is the first time someone has demonstrated this."
As the scientists explain, previous research has shown that olfactory brain receptors can pick up not only smell but also small variations in airflow, with different parts of the brain being activated upon inhalation and exhalation.
However, scientists do not currently know how different breathing patterns affect human behavior.
"The idea that breathing affects our behavior is actually not new," says Arshamian. "In fact, the knowledge has been around for thousands of years in such areas as meditation."
"But no one has managed to prove scientifically what actually goes on in the brain," he explains. "We now have tools that can reveal new clinical knowledge."
Using these new tools, Arshamian and his colleagues plan to discover the exact mechanism responsible for the effect that breathing has on olfactory memory.
"The next step is to measure what actually happens in the brain during breathing and how this is linked to memory," says the study's lead author.
"This was previously a practical impossibility as electrodes had to be inserted directly into the brain. We've managed to get round this problem and now we're developing, with my colleague Johan Lundström, a new means of measuring activity in the olfactory bulb and brain without having to insert electrodes."