We sigh when we're stressed, when we're in love and when we practice yoga and meditation -- but that's not all. Our brains signal for us to sigh every five minutes, often without us even realizing it. (Seriously, listen to your own breaths in a quiet room, it's like clockwork.)
Sighing, or breathing more deeply than normal, is a vital part of our everyday lives, as it helps preserve the health and function of our lungs. But exactly where our sighs originate in the brain has been somewhat of a mystery -- until now.
A team of researchers at Stanford University and the University of California, Los Angeles, has pinpointed two clusters of neurons in the brain stem that are responsible for the deep exhalations, outlined in a new study published in the journal Nature on Monday.
Converting our normal breaths into sighs is regulated by the fewest number of neurons yet seen linked to a fundamental human behavior, said research co-author Dr. Jack Feldman, a professor of neurobiology at the David Geffen School of Medicine at UCLA.
"This work was very exciting to us," Feldman told The Huffington Post. "You breathe 600 million times in a lifetime, how does the nervous system do that? ... We’re hoping that in understanding breathing we can find some basic principles in how the mammalian, including human, brain is working to produce more complex behaviors."
The researchers examined more than 14,000 gene-expression patterns in the brain cells of mice. From there, they pinpointed roughly 200 neurons in the lower part of the brain stem that contain two specific neuropeptides, which are molecules that brain cells use to communicate with each other.
Another cluster of 200 neurons contains peptide receptors that are activated by the neuropeptides, which leads to the triggering of breathing behavior.
The neuropeptides are so powerful that when the researchers injected one of the molecules, a bombesin-related neuropeptide, into mice, it increased the rodents' sigh rate by more than 10 times. The mice went from sighing 40 times an hour to 400 times an hour. Also, inhibiting both peptides halted the mice’s ability to sigh completely.
The researchers concluded that the two peptides send signals to the neurons in the brain circuit to control our breathing and produce sighs.
The circuit regulates how fast we breathe and the types of breaths we take, from sighs to coughs to yawns, Dr. Mark Krasnow, professor of biochemistry at Stanford University and a co-author of the study, said in a statement.
A better understanding of this brain circuit could lead to treatments for breathing-related disorders. For instance, people with anxiety disorders may sigh too much or people who have difficulty breathing due to heart problems could benefit from additional sighs.
"These molecular pathways are critical regulators of sighing, and define the core of a sigh-control circuit," Krasnow said. "It may now be possible to find drugs that target these pathways to control sighing."
Feldman not only agrees, but also thinks that this new research could lead to even more groundbreaking studies that unravel the complex science behind how our brain can regulate our every move.
"Breathing is very important to life and it’s also a window into trying to understand how the brain produces behavior," he said.
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