A new study led by researchers at the University of California San Diego shows that the brain does not simply respond to breathing as a steady rhythm. Instead, the detailed shape of each individual breath is closely linked to the shape of neural activity in brain regions involved in cognition, emotion and memory.
The findings, published in the Journal of Neuroscience, suggest that the brain is tracking the subtle variations that occur from one breath to the next. A longer inhale, a slower exhale or other changes in the timing and intensity of a breath are reflected in corresponding patterns of neural activity, revealing a much more precise connection between breathing and the brain than traditional measures such as breaths per minute can capture.
"Every single breath is different," said the paper's first author Eena Kosik-Rose, a PhD student in the UC San Diego School of Social Sciences' Department of Cognitive Science . "You can pause your breathing for several seconds, take a super deep breath or have a shallow exhale. What we're showing is that those differences in the shape of each breath are reflected in the shape of brain activity."
At its core, the research asks a question rooted in cognitive science and the study of human behavior: How does something as seemingly automatic as breathing interact with the brain processes that shape thought, emotion and perception?
Researchers have already found that the timing of breathing can influence attention and memory. In one example, people perform slightly better on a memory task when they encounter information while inhaling rather than exhaling. Breath control is also used as a tool to help calm people experiencing symptoms of PTSD.
"Our results show that the coupling between breathing and neural activity is much richer than previously appreciated," said Bradley Voytek, study coauthor and professor and chair of the Department of Cognitive Science.
To visualize this relationship, the authors of the paper represented each breath as a wave-like pattern, with the rises and falls corresponding to changes in airflow as a person inhales and exhales. They then compared the shape of each respiratory wave with the corresponding pattern of electrical activity in the brain. Unlike a simple measure of breathing rate, this approach captures the subtle differences in timing, volume and shape from one breath to the next.
New Possibilities for Understanding Breathing and the Brain
The findings provide a new way to study one of the body's most fundamental rhythms and could eventually help researchers better understand conditions in which the relationship between breathing and the brain goes dangerously awry such as in sudden unexpected death in epilepsy (SUDEP) and sudden infant death syndrome (SIDS).
The study analyzed invasive brain recordings from 16 people undergoing clinical monitoring for treatment-resistant epilepsy. Researchers compared electrical activity recorded directly from the brain with measurements of each person's breathing, including nasal airflow and movement of the chest and abdomen.
One of the study's co-authors, Brian Dlouhy, a neurosurgeon at the University of Iowa, studies SUDEP — a devastating phenomenon in which people with epilepsy can die suddenly. In an interview about the research, Voytek described a future direction for the team: examining whether the breathing-brain relationship identified in this study becomes disrupted in SUDEP and whether changes in the shape of breathing could provide an early signal that breathing is about to stop.
"Future research could investigate whether the breathing pattern provides a warning that breathing is about to stop in SUDEP or SIDS, said Voytek, who has affiliations in the School of Medicine's Neurosciences Graduate Program and the Halıcıoğlu Data Science Institute in the Halıcıoğlu School of Data Science and Computing.
The researchers emphasize that the current study does not establish a method for predicting SUDEP or SIDS. Instead, it provides a potential framework for future studies aimed at determining whether disruption of the normal breathing-brain relationship plays a role in these conditions.
For UC San Diego, the collaboration on the paper highlights how research into human cognition can generate questions with implications that reach well beyond the traditional boundaries of the social sciences — potentially contributing to some of medicine's most difficult challenges.
"Now that we know that there is this incredibly tight and rich coupling between the shape of each breath and the shape of each brainwave, there's a whole new world of options that we can explore," Voytek said.
Because the current study relied on highly precise intracranial recordings from people undergoing epilepsy monitoring, the findings will also need to be tested using noninvasive methods and in broader populations.
Still, the central insight is simple: A breath is more than a number.
Each inhale and exhale carries information and the brain appears to track that information with remarkable precision — breath by breath, cycle by cycle.
Read the full paper, "Cycle-by-cycle respiration waveforms are coupled with the shape of neural oscillations."
