Nose breathing improves the transfer of experience to long-term memory, according to a new study published in the journal JNeurosci.
Arshamian et al examined the effect of respiration on consolidation of episodic odor memory.
“Memories pass through three main stages in their development: encoding, consolidation, and retrieval,” said lead author Dr. Artin Arshamian of Karolinska Institutet and colleagues.
“Growing evidence from animal and human studies suggests that respiration plays an important role in the behavioral and neural mechanisms associated with encoding and recognition.”
“Specifically nasal, but not mouth, respiration entrains neural oscillations that enhance the encoding and recognition processes.”
Building on previous research in animals and humans, the team compared the effects of nose and mouth breathing during a one-hour consolidation period after participants were exposed to various odors.
Nose breathers, whose mouths were taped over during the consolidation period, showed increased odor recognition compared to mouth breathers, whose noses were clipped during consolidation.
“The experiment consisted of two separate sessions, each including an encoding, a consolidation, and a recognition phase,” the scientists explained.
“In the encoding phase, participants were presented with six familiar (e.g., strawberry) and six unfamiliar (e.g., 1-butanol) odors one at a time and asked to remember them. The odors familiarity was pre-defined and a new set of odors were used in each session.”
“After the encoding phase, participants rested passively without sleeping (consolidation phase) for one hour during which they either breathed through their nose (nasal consolidation) or mouth (mouth consolidation).”
“Next, during the odor recognition phase, participants were once again presented with the odors from the encoding phase but this time intermixed with 12 new odors (6 familiar and 6 unfamiliar odors). For each odor, participants made a recognition judgment if the odor was new or old.”
“Participants then rated odor intensity, pleasantness, familiarity, and nameability, as well tried to identify the odor.”
“During both encoding and recognition, nasal airflow was monitored by a nasal cannula which enabled measurement of sniff parameters during odor presentation.”
Although the study did not measure brain activity, the researchers suggest that nose breathing may facilitate communication between sensory and memory networks as memories are replayed and strengthened during consolidation.
“Our results provide the first evidence that respiration directly impacts consolidation of episodic events, and lends further support to the notion that core cognitive functions are modulated by the respiratory cycle,” the study authors said.
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Artin Arshamian et al. Respiration modulates olfactory memory consolidation in humans. JNeurosci, published online October 22, 2018; doi: 10.1523/JNEUROSCI.3360-17.2018
