Neurons identified that link breathing to relaxation and arousal

By Kate Bass, B.Sc.Mar 31 2017

Deep breathing is widely considered as one of the best ways to lower stress in the body and instil a sense of calm. Scientists at Stanford University have now identified the neurons that connect the respiratory control center in the brain with the centre controlling state of mind.

Breathing slowly and coordinating breathing patterns are hallmarks of relaxation and the ever-increasing scientific evidence base supports the health benefits of slow, deep breathing. It is known that a slow respiratory rate improves cardiovascular and respiratory function, improves blood oxygenation, enhances exercise tolerance, and increases the sense of calmness and well-being. In contrast, rapidly or frenetic breathing can give rise to a state of increasing tension or arousal. However, it was not known how the change in number of breath cycles per minute effected a change in mood.

In a paper published today in Science, researchers from Stanford University School of Medicine describe a small cluster of neurons that links breathing pattern to relaxation, attention, excitement and anxiety. Their findings provide, for the first time, a cellular and molecular understanding of the mechanisms by which breathing-control exercises can relieve stress disorders and through which the practice of pranayama can achieve a meditative state.

The researchers set out to determine whether different subtypes of neurons within the respiratory control center were responsible for generating different types of breath, such as regular, excited, sighing, yawning, sleeping, laughing. Having identified more than 60 different neurons in the respiratory control centre of the mouse, populations of laboratory mice that had just one of these neurons missing were developed in order to investigate the role of each type of neuron.

In 2016, they identified the neurons that explicitly controls sighing. Eliminating a particular subpopulation of neurons rendered a mouse unable to sigh but left other modes of breathing unaffected. They now report that elimination of another subpopulation of neurons did not reduce the range of breathing types in the mouse. Instead, removal of this particular subpopulation of neurons made the mice extraordinarily calm.

Lead author, and former Stanford graduate student, Kevin Yackle remarked "If you put them in a novel environment, which normally stimulates lots of sniffing and exploration, they would just sit around grooming themselves”.

Further investigations revealed that the removed neurons were responsible for relaying information regarding breathing rate to the locus coeruleus, which regulates the level of arousal.

Senior Author and professor of biochemistry, Mark Krasnow, explained "If something’s impairing or accelerating your breathing, you need to know right away. These 175 neurons, which tell the rest of the brain what’s going on, are absolutely critical".

Discovering the key role these neurons play in coordinating changes in breathing with effects on arousal and emotion may facilitate the development of new therapies for stress, depression and other negative emotions.