A recent neuroimaging study has identified a link between respiration and neural activity changes in rats. The findings, which have been published in the journal eLife, suggest that breathing might modulate neural responses across the brain.
“Breathing is an essential physiologic process for a living organism,” said study author Nanyin Zhang, the Lloyd & Dorothy Foehr Huck Chair in Brain Imaging and director of the Center for Neurotechnology in Mental Health Research at Penn State.
“Scientists know that respiration is controlled by the brain stem, and the breathing process can modulate neural activity changes in several brain regions. However, people still do not have a comprehensive picture about brain-wide regions involved during breathing. This question can in principle be answered using a technique called functional magnetic resonance imaging (fMRI), a non-invasive neuroimage method that allows us to map neural activity in the whole brain.”
“The challenge is, however, fMRI is also sensitive to non-neural factors accompanied by breathing such as motion and CO2 fluctuations in the brain, which can lead to artifacts in fMRI data. As a result, how to map breathing-associated neural network using fMRI is largely unexplored.”
In tandem with fMRI, the researchers measured electrical signals in the nervous system and used a respiration sensor to examine rodents in a resting state. This method allowed the researchers to filter out potential artifacts and pinpoint where breathing-related neural activity occurs in the brain.
“We hope to reveal how breathing can modulate the neural activity across the whole brain,” Zhang told PsyPost. “This knowledge will help elucidate the contribution of breathing on neuro and neuro-vascular signals at rest. The findings provide insight into the respiration-mediated relationship between brain activity and non-invasive fMRI measures.”
The researchers found that breathing was associated with a particular pattern of brain activity that can be distinguished from the artifacts introduced by CO2 fluctuations and body movements.
“We discovered a respiration-associated brain network mediated by neural activity based on the resting-state fMRI, electrophysiology and respirational signals measured at the same time in rats,” Zhang explained. “The respiration signal is associated with the gamma-band neural activity in the cingulate cortex, and both the gamma and respiration signals correlate with distributed neuronal networks measured by fMRI.”
“Additionally, this ‘respiration network’ disappeared when the brain-wide neural activity was suppressed at an isoelectric state while the respiration was maintained, further indicating the neural underpinning of this network. This study for the first time mapped the brain-wide neural responses modulated by respiration.”
The researchers said that this breathing-related brain network could be implicated in various brain disorders, “and thus our findings might potentially provide important clinical value.”
In a news release, Zhang said that the relationship between neural activity in the cingulate cortex and breathing rhythm may indicate that breathing rhythms may impact emotional states.
“When we are in an anxious state, often our breathing speeds up,” Zhang said. “In response, we sometimes take a deep breath. Or when we are focusing, we tend to hold our breath. Those are signs that breathing can impact our brain function. Breathing allows us to control our emotions, for example, when we need our brain function to alter. Our findings support that idea.”
Future studies may focus on observing brain activity in human subjects while they are meditating. One integral part of meditation is focusing on your breathing, which acts as an anchor to remain in the present moment.
“Our understanding of what is happening in the brain is still superficial,” Zhang said. “If researchers replicate the study on humans using the same techniques, they might be able to explain how meditation modulates neural activity in the brain.”
The study, “Neural underpinning of a respiration-associated resting-state fMRI network“, was authored by Wenyu Tu and Nanyin Zhang.