Breathing easy

Respiratory ‘pacemaker’ linked to state of tranquility

SAN FRANCISCO — Researchers at the Stanford University School of Medicine have identified a handful of nerve cells in the brainstem that connect breathing to states of mind. The finding, published in the journal Science, explains how slow breathing induces tranquillity.

Medical practitioners sometimes prescribe breathing control exercises for people with stress disorders. Similarly, the practice of pranayama, controlling breath in order to shift one’s consciousness from an aroused or even frantic state to a more meditative one, is a core component of virtually all varieties of yoga.

The tiny cluster of neurons linking respiration to relaxation, attention, excitement and anxiety is located deep in the brainstem. This cluster, located in an area Mark Krasnow, professor of biochemistry at Stanford, calls the pacemaker for breathing, was discovered in mice by a study co-author Jack Feldman, a professor of neurobiology at University of California, Los Angeles, who published his findings in 1991. An equivalent structure has since been identified in humans.

The lead author of the new study is former Stanford graduate student Kevin Yackle, now a faculty fellow at the University of California, San Francisco.

The preB tC now appears to play a key role in the effects of breathing on arousal and emotion.” Jack Feldman, study co-author

“The respiratory pacemaker has, in some respects, a tougher job than its counterpart in the heart,” Krasnow was quoted as saying in a news release.

“Unlike the heart’s one-dimensional, slow-to-fast continuum, there are many distinct types of breaths: regular, excited, sighing, yawning, gasping, sleeping, laughing, sobbing. We wondered if different subtypes of neurons within the respiratory control center might be in charge of generating these different types of breath.”

On that hunch, Yackle searched through public databases to assemble a list ofgenes that are preferentially activated in the part of the mouse brainstem where the breathingcenter resides.

The center’s technical term is the pre-B tzinger complex, or preB tC. He pinpointed a number of such genes, allowing the investigators to identify more than 60 separate neuronal subtypes, physically differentiated from one another by their gene-activation signatures but commingling in the preB tC like wellstirred spaghetti strands.

The researchers used these genes, and the protein products for which they are recipes, as markers allowing them to zero in on the different neuronal subtypes.

Krasnow and Yackle also discovered that bioengineered mice became more relaxed after certain neurons were eliminated.

“The preB tC now appears to play a key role in the effects of breathing on arousal and emotion, such as seen during meditation,” said Feldman. “We’re hopeful that understanding this center’s function will lead to therapies for stress, depression and other negative emotions.”