Breathing can measurably modulate neural responses in the brain

Abstract: The study reveals a potential link between breathing and changes in neural activity in animal models.

Source: Penn State

Mental health professionals and meditation gurus have long credited intentional breathing with the ability to induce inner calm, but scientists don’t fully understand how the brain is involved in the process.

Using functional magnetic resonance imaging (fMRI) and electrophysiology, researchers from the Penn State College of Engineering have identified a potential link between breathing and changes in neural activity in rats.

Their results were available online before publication in eLife. The researchers used simultaneous multimodal techniques to remove the noise commonly associated with brain imaging and determine where breathing regulates neural activity.

“There are approximately one million papers published on fMRI — a noninvasive imaging technique that allows researchers to examine brain activity in real time,” said Nanyin Zhang, founder of Penn State’s Center for Neurotechnology in Mental Health Research and professor of biomedical engineering.

“Imaging researchers believed that breathing was a non-neural physiological artifact, like heartbeat or body movement, in fMRI imaging. Our work introduces the idea that breathing has a neural component: it affects the fMRI signal by modulating neural activity.”

By scanning the brain waves of resting, anesthetized rodents using fMRI, the researchers discovered a network of brain regions involved in breathing.

“Breathing is a need common to almost all living animals,” Zhang said. “We know that breathing is controlled by a region in the brain stem. But we didn’t have a complete picture of how breathing affects other regions of the brain.”

In tandem with fMRI, the researchers used neural electrophysiology, which measures electrical properties and signals in the nervous system, to link breathing with neural activity in the cingulate cortex—a brain region in the center of the cerebral hemisphere associated with emotional response and regulation.

Using fMRI and electrophysiology simultaneously allowed the researchers to detect changes in the fMRI signal unrelated to the nervous system during data collection, such as movements and carbon dioxide exhales.

The findings provide insight into how neural activity and fMRI signals are linked at rest, Zhang said, which could inform future imaging studies in understanding how neurovascular signals change while at rest.

“While the animals were breathing, we measured how their brain activity fluctuated with their breathing rhythm,” Zhang said. “When extended to humans, this approach could provide mechanistic insight into how breathing control common to meditation practices can help reduce stress and anxiety.”

The correlation between neural activity in the cingulate cortex and breathing rhythm may indicate that breathing rhythms can affect emotional state, according to Zhang.

“When we are in an anxious state, our breathing often becomes faster,” Zhang said. “In response, we sometimes take a deep breath. Or when we focus, we tend to hold our breath. These are signs that breathing can affect the work of our brain. Breathing allows us to control our emotions, for example, when we need to change how our brain works. Our findings support that idea.”

Future studies could focus on looking at the brains of people while they meditate to analyze a more direct link between slow, deliberate breathing and neural activity, according to Zhang.

“Our understanding of what happens in the brain is still superficial,” Zhang said. “If researchers replicate the study in humans using the same techniques, they may be able to explain how meditation modulates neural activity in the brain.”

About this neuroscience research news

Author: Mariah Chuprinski
Source: Penn State
Contact: Mariah Chuprinski – Penn State
Picture: The image is in the public domain

Original research: Open access.
“Neural basis of the breathing-related resting-state fMRI network” Wenyu Tu et al. eLife

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Abstract

Neural basis of the breathing-related resting-state fMRI network

Breathing can stimulate movement and CO₂ fluctuations during resting-state fMRI (rsfMRI) scanning, which will lead to non-neural artifacts in the rsfMRI signal. Meanwhile, as a key physiological process, breathing can directly induce a change in neural activity in the brain, and thus can modulate the rsfMRI signal.

Nevertheless, this potential neural component in the breathing-fMRI relationship is largely unexplored. To clarify this question, here we simultaneously recorded electrophysiology, rsfMRI, and respiratory signals in rats.

Our data show that breathing is indeed associated with changes in neural activity, as evidenced by the phase relationship between variations in slow breathing and gamma-band power of the electrophysiological signal recorded in the anterior cingulate cortex.

Intriguingly, slow breathing variations are also associated with a characteristic rsfMRI network, which is mediated by gamma-band neural activity. In addition, this breathing-related brain network disappears when whole-brain neural activity is silenced in the isoelectric state while breathing is maintained, further confirming the necessary role of neuronal activity in this network.

Taken together, this study identifies a breathing-related brain network supported by neural activity that represents a novel component in the breathing-rsfMRI relationship that is distinct from breathing-related rsfMRI artifacts. It opens a new avenue for investigating the interactions between breathing, neural activity, and resting-state brain networks in healthy and diseased states.