The Vital crosstalk between Breath and Brain

If you’re lucky enough to live to 80, you’ll take up to a billion breaths in the course of your life, inhaling and exhaling enough air to fill about 50 Goodyear blimps or more. We take about 20,000 breaths a day, sucking in oxygen to fuel our cells and tissues, and ridding the body of carbon dioxide that builds up as a result of cellular metabolism. Breathing is so essential to life that people generally die within minutes if it stops.

Breathing can also influence your state of mind, as evidenced by the controlled breathing practices of yoga and other ancient meditative traditions.

In recent years, researchers have begun to unravel some of the underlying neural mechanisms of breathing and its many influences on body and mind. In the late 1980s, neuroscientists identified a network of neurons in the brainstem that sets the rhythm for respiration. That discovery has been a springboard for investigations into how the brain integrates breathing with other behaviors. At the same time, researchers have been finding evidence that breathing may influence activity across wide swaths of the brain, including ones with important roles in emotion and cognition. “Breathing has a lot of jobs.” “It’s very complicated because we’re constantly changing our posture and our metabolism, and it has to be coordinated with all these other behaviors.” At rest, these muscles contract only during inhalation. Exhalation occurs passively when the muscles relax and the lungs deflate. During exercise, different sets of muscles contract to actively force out air and speed up respiration. Unlike the heart muscle, which has pacemaker cells that set its rhythm, the muscles that control breathing take their orders from the brain.

Sighing is one interesting example. A long, deep breath can express many things: sadness, relief, resignation, yearning, exhaustion. But we humans aren’t the only ones who sigh — it’s thought that all mammals do — and it may be because sighing has an important biological function in addition to its expressive qualities. Humans sigh every few minutes, and each sigh begins with an inhale that takes in about twice as much air as a normal breath. Scientists suspect this helps pop open collapsed alveoli, the tiny chambers in the lung where gas exchange occurs, much as blowing into a latex glove pops open the fingers. Several lines of evidence support this idea: Hospital ventilators programmed to incorporate periodic sighing, for example, have been shown to improve lung function and maintain patients’ blood oxygen levels.

The preBötC also has a role in coordinating other behaviors with breathing. One of Feldman’s collaborators on the sighing paper, neuroscientist Kevin Yackle, and colleagues recently used mice to investigate interactions between breathing and vocalizations. When separated from their nest, newborn mice make ultrasonic cries, too high-pitched for humans to hear. There are typically several cries at regular intervals within a single breath, not unlike the syllables in human speech, says Yackle, who’s now at the University of California, San Francisco. “You have this slower breathing rhythm and then nested within it you have this faster vocalization rhythm,” he says.

To figure out how this works, the researchers worked their way backwards from the larynx, the part of the throat involved in producing sound. They used anatomical tracers to identify the neurons that control the larynx and follow their connections back to a cluster of cells in the brainstem, in an area they named the intermediate reticular oscillator (iRO). Using a variety of techniques, the researchers found that killing or inhibiting iRO neurons removes the ability to vocalize a cry, and stimulating them increases the number of cries per breath.

When the researchers dissected out slices of brain tissue with iRO neurons, the cells kept firing in a regular pattern. “These neurons produce a rhythm that’s exactly like the cries in the animal, where it’s faster than but nested within the preBötC breathing rhythm,” Yackle says.

Additional experiments suggested that iRO neurons help integrate vocalizations with breathing by telling the preBötC to make tiny inhalations that interrupt exhalation — enabling a series of brief cries to fit neatly within a single exhaled breath. That is, rhythmic crying isn’t produced by a series of exhalations, but rather from one long exhalation with several interruptions.

One study found that people tend to inhale just before a cognitive task — and that doing so tends to improve performance. Around the same time, neuroscientist Christina Zelano and colleagues reported similar findings in humans. Using data from electrodes placed by surgeons on the brains of epilepsy patients to monitor their seizures, the researchers found that natural breathing synchronizes oscillations within several brain regions, including the hippocampus and the amygdala, an important player in emotional processing. This synchronizing effect diminished when the researchers asked subjects to breathe through their mouth, suggesting that sensory feedback from nasal airflow plays a key role.

For millennia, practitioners of yoga and other ancient meditation traditions have practiced controlled breathing as a means of influencing their state of mind. In recent years, researchers have become increasingly interested in the biological mechanisms of these effects and how they might be applied to help people with anxiety and mood disorders.

One challenge has been separating the effects of breathing from other aspects of these practices, says Helen Lavretsky, a psychiatrist at UCLA. “It’s really hard to distinguish what’s most effective when you’re doing this multi-component intervention where there’s stretching and movement and visualization and chanting,” she says. Not to mention the cultural and spiritual components many people attach to the practice.

For many years, Lavretsky has collaborated with neuroscientists and others to investigate how different types of meditation affect the brain and biological markers of stress and immune function. She has found, among other things, that meditation can improve performance on lab tests of memory and alter brain connectivity in older people with mild cognitive impairment, a potential precursor to Alzheimer’s disease and other types of dementia. In more recent studies, which have yet to be published, she’s moved toward investigating whether the breath control methods alone can help.

“Even though I’m a psychiatrist, my research is on how to avoid [prescribing] drugs,” says Lavretsky, who is also a certified yoga instructor. She thinks breathing exercises might be a good alternative for many people, especially with more research on which breathing techniques work best for which conditions and how they might be tailored to individuals. “We all have this tool, we just have to learn how to use it,” she says.

Discover Magazine, https://www.discovermagazine.com/the-sciences/the-vital-crosstalk-between-breath-and-brain

Author, Greg Miller