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The gut–brain axis is a communication network that links the central nervous system and the gastrointestinal (GI) tract. Sensory signals are received by the brain from the stomach via afferent nerve fibers, which trigger neurological responses that are fed back to the periphery via efferent nerve fibers. Sensations such as feeling full or hungry are attributed to the processes of the gut–brain axis.
The vagus nerve – sometimes referred to as “the wandering nerve” due to its long, winding pathway through the human body – is a key player in the gut–brain axis. Receptors located in the stomach wall trigger signals regarding how “full” the stomach is, which are delivered to the brain via the vagus nerve. Once processed, these signals are relayed via efferent vagal signaling to the GI smooth muscle, helping to modulate muscle movement and aid digestion.
The role of the vagus nerve in regulating digestion speed is well understood. However, whether vagal stimulation can lead to more widespread effects across the brain, affecting regions that are involved in higher-order cognitive functions, like goal-directed behavior, wasn’t known – until now.
Professor Nils Kroemer, researcher in the neuroMADLAB at the University Hospitals of Tübingen and Bonn, studies the neurobiological principles of motivation, action and desire. Earlier this year, Kroemer and colleagues published a study that showed – for the first time – how non-invasive stimulation of the vagus nerve can strengthen the communication between the stomach and the brain within minutes. Using non-invasive techniques to record the stomach and the brain, the researchers were also able to demonstrate how this coupling effect spreads across sub-cortical and cortical regions of the brain. The findings could have therapeutic applications, as some mental disorders are characterized by reduced sensory input to the brain.