Link between muscle movement and breathing rhythms may shed new light on SIDS and sleep apnea

Between 2,000 and 3,000 infant deaths each year are attributed to Sudden Infant Death Syndrome (SIDS), according to the American Academy of Pediatrics. In addition, approximately 12 million Americans suffer from sleep apnea, a respiratory ailment that can lead to death in some cases.

A new study from a University of Missouri-Columbia researcher, scheduled to be published in the Journal of Neuroscience later this spring, explores the link between muscle movement and breathing rhythms that may shed new light on respiratory disorders, such as SIDS and sleep apnea.

"When you move, changes occur in your breathing rhythms," said Jeffrey Potts, an associate professor of veterinary biomedical science and research investigator at the Dalton Cardiovascular Research Center. "For example, during physical exercise you breathe faster and deeper, but you don't consciously think about it because these changes occur automatically. In our research, we found that specific types of neurons play a crucial role in establishing breathing rhythms during exercise."

Potts and his colleagues are studying different neural pathways that tell the brain about the movements of the human body. Potts is specifically interested in how these signals alter the way humans breathe.

For his study, Potts focused on regions of the brain that are crucial for breathing. These regions contain distinct populations of respiratory neurons that establish normal breathing patterns. These groups of neurons are called the pontine and medullary respiratory groups. When activated, these regions establish rhythmic neural signals that are sent to a group of neurons located in the phrenic motor nucleus of the spinal cord. The phrenic motor nucleus then determines whether breathing muscles should contract or relax, depending on the body's immediate need to breathe.

During his research, Potts discovered that the movement of limb muscles stimulated a response in the brain that changed breathing patterns. He found these pathways by simulating skeletal muscle and then observing whether certain groups of respiratory neurons were activated. Potts’ group found that changes in breathing patterns involved a neural pathway from skeletal muscle to respiratory neurons in the medulla by way of the pontine respiratory group.

“Neurons in the pontine respiratory group have long been known to play an important role in the timing of normal breathing patterns," Potts said. "However, our findings are the first to identify that pontine neurons also play a crucial role in the timing of breathing rhythms during muscle movements associated with exercise."

Potts identified multiple connections, or synapses, that are required to make a change in breathing pattern. His findings could have implications for researchers studying other physiological or disease states, such as breathing disorders. By identifying these neural pathways, scientists may be able to learn more about conditions that are associated with alterations in the normal processing of signals by these pathways, such as may occur in SIDS or sleep apnea. Potts' research is funded by the National Institutes of Health, the American Heart Association and the Children's Hospital of Michigan.