Vagus Nerve Stimulation Strengthens Gut-Brain Connection

The vagus nerve is critical to the parasympathetic nervous system, which controls subconscious bodily functions such as heart rate, blood pressure, digestion, and more. Previous research has revealed how the vagus nerve also plays an essential role in endogenous signaling to the enteric nervous system, one of the many facets of humans’ gut-brain connection. To further understand this stomach-brain coupling, researchers investigated how non-invasive vagal stimulations regulated digestion.

The team consisted of scientists from the universities of Tübingen and Bonn, the German Institute of Human Nutrition in Potsdam, and the German Center for Diabetes Research. Their work, published in Brain Stimulation, began by recording brain activation via fMRI and electrogastrogram of 31 participants. The electrogastrogram is similar to an ECG, where researchers place electrodes over the stomach to record signals from the digestive tract.

“We showed for the first time that electrical stimulation strengthens the coupling between signals from the stomach and the brain – and we can do it within a few minutes,” says co-author Professor Kroemer, leader of neuroMADLAB at the University Hospital of Tübingen and Professor of Medical Psychology at the Department of Psychiatry and Psychotherapy at the University of Bonn.

Each participant had an electrode placed on their ear to measure vagus nerve signal fluctuations. “We observed that vagus nerve stimulation increased coupling with signals from the stomach in the brainstem and midbrain,” explains Prof. Kroemer. “These regions are important because they are the first targets of the vagus nerve in the brain. Changes in the midbrain may already mediate our actions.”

The team also found that brain areas experiencing the most robust coupling with the stomach were those that already communicate more frequently with the stomach before stimulation. However, changes in coupling between the brain and gut were observed almost instantaneously and spread rapidly.

These findings present new avenues of treatment for depression, anxiety, and eating disorders. For future work, Professor Kroemer’s lab is working on possible applications for clinical depression, where miscommunication between the brain and body are considered core symptoms. Additionally, vagus nerve stimulation has previously been shown to restore the perception of body signals in individuals struggling with obesity, so it is worth investigating further in future work.