There has long been a discussion about the human digestive system functioning as a second brain. Studies have revealed the gut can pass messages back to the brain and that it may even influence our choices on a daily basis.

Unique neural motor firing pattern

A team of researchers at Flinders University, Adelaide, Australia have finally observed a unique neural motor firing pattern in the intestine that illustrates how the human enteric nervous system coordinates contractions in the gastrointestinal tract. “The enteric nervous system (ENS) is known as the "second brain" or the brain in the gut because it can operate independently of the brain and spinal cord, the central nervous system (CNS),” said a statement released by Flinders University.

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The ENS is one of the main divisions of the autonomic nervous system and is composed of a mesh-like system of neurons that control the gastrointestinal tract. Outside of the brain, it consists of the largest collection of neurons found in the human body and has even been referred to as the "first brain" based on evidence suggesting that it may have evolved before the CNS.

In a paper, published in the the Society for Neuroscience's first journal JNeurosci, a team led by professor of medicine and public health at Flinders University, Nick Spencer, “combined a new neuronal imaging technique with electrophysiology records of smooth muscle to reveal a pattern of activity that involves many different types of neurons firing simultaneously in repetitive bursts.” The study illustrates a previously unknown pattern of neuronal rhythmic activity in the peripheral nervous system that is responsible for migrating motor complexes that transport fecal matter through the colon.

Introducing Neurogastroenterology

Recent research in the broader applications of the second brain has resulted in the introduction of the field of Neurogastroenterology, the study of abnormalities in gut neuromuscular function and complex brain-gut interactions. Although much remains to be discovered, scientists currently know that ENS is in charge of many of the human body’s neurotransmitters such as 95% of the body's serotonin.

Recent studies have also pointed to a peculiar connection between brain injury and intestinal damage. "These results indicate strong two-way interactions between the brain and the gut that may help explain the increased incidence of systemic infections after brain trauma and allow new treatment approaches," said University of Maryland School of Medicine lead researcher Alan Faden.

As more is revealed about the extent of the effects of the human body's second brain, the expression "gut feeling" may come to take on an entirely new meaning. In the meantime, we can start by taking the hangry state a little more seriously.

This is the second discovery pertaining to the colon made by Spencer's team in May 2018. A collaboration with Washington University saw the team achieve a technical breakthrough in an optogenetics technique with the potential to replace drugs as a remedy to gastrointestinal conditions.