researchers identify a brain circuit linking breathing and emotional calming

Stress, anxiety, fear — these intense emotions can lead to hyperventilation, also known as “anxious breathing.” To stabilize this emotional turbulence, regulating breathing through meditation or yoga exercises is an effective method. A recent study explored how consciously slowing breathing can help return to a stable emotional state, revealing a brain circuit that may be heavily involved. According to researchers, a group of neurons, connected to the brainstem, coordinates breathing with emotional state. An advance that opens the way to targeted treatments for hyperventilation and post-traumatic stress disorders.

Severe hyperventilation syndrome often manifests itself during anxiety attacks or stressful episodes. Although generally not serious, it remains debilitating, because individuals try to compensate for a feeling of lack of air by breathing more quickly and deeply. This increase in oxygen levels can lead to visual disturbances, dizziness and flushing and, if left unchecked, tetany (loss of muscle control) followed by discomfort. Various wellness disciplines recommend slow breathing exercises, inspired by yoga or meditation, to soothe this syndrome.

Mark Krasnow, a professor of biochemistry at Stanford University, supports these practices, saying that mastering deep breathing provides relaxing effects to the body. In 2017, Krasnow and colleagues conducted a study aimed at better understanding how awareness of breathing can ease hyperventilation.

Through experiments on mouse models, they discovered a set of neurons at the base of the brainstem involved in the communication between breathing and relaxation. In their study, published in the National Library of Medicine, they write: “
We identified a neuronal subpopulation in the mouse pre-Bötzinger complex (preBötC), the main generator of the respiratory rhythm, which regulates the balance between calm and arousal behaviors ».

In a more recent study, neuroscientists at the Salk Institute further explored the conscious mechanisms of respiratory regulation in the brainstem. “ The body naturally self-regulates through deep breathing. Harmonizing our breathing with our emotions seems intuitive to us, but we didn't know how it works in the brain », Explains Sung Han, lead author of the study, in a press release.

Recognizing the indiscernible but obvious link between breathing patterns and emotional state, Han and his team hypothesized the involvement of the brain's frontal cortex, known for orchestrating thoughts and behaviors. This cortex interacts with the spinal cord, responsible in particular for autonomous breathing. To corroborate this hypothesis, the team carried out experiments on mouse models.

In their study, published in the journal Nature
Neurosciencethe researchers describe having carefully traced the connections between different brain areas, based on the analysis of a database of neuronal connectivities. They discovered a new respiratory circuit involved in the stimulation of the emotional state, then identified neurons located in the anterior cingulate cortex which are connected directly to an intermediate area of ​​the brainstem in the pons, itself connected to the spinal cord. spinal cord.

« By uncovering a specific brain mechanism responsible for slowing breathing, our discovery could offer a scientific explanation for the beneficial effects of practices like yoga and mindfulness on alleviating negative emotions, further grounding them in science says Han.

Towards a better understanding of the communication between cortical neurons and the spinal cord

This first experiment allowed researchers to understand the physical connections between these different brain areas. The researchers then explored how they communicate and how activation of the spinal cord might influence breathing. To do this, they recorded the brain activity of mouse models during a series of experiments, exposing them to various stressful situations modifying their behavior. To artificially activate and deactivate part of the neurons in the cortex-pont-medullary circuit, the team used optogenetics.

The results supported the initial hypothesis. The scientists found that when the connection was made between the cortex and the pons, the mice behaved calmly and breathed slowly. On the other hand, when faced with intense stress, this communication weakened, leading to an increase in respiratory frequency. By optogenetically activating the anterior cingulate cortex-pons-medullary circuit, respiratory rate was normalized and anxiety dissipated.

« I want to use these results to design a 'yoga pill' », Han announced. « We now have a potentially targetable brain circuit to create therapies that can instantly slow breathing and initiate a peaceful, meditative state », he concludes.

Source : Nature Neuroscience