The nervous system takes in sensory stimuli, processes them and triggers reactions such as muscle movements or pain sensations. A few years ago, a network in the brain was identified that is coupled with signals from the stomach and presumably influences the human feeling of hunger and satiety. Now, a research team led by Prof. Dr. Nils Kroemer of the University Hospitals of Tübingen and Bonn has shown for the first time that non-invasive stimulation of the vagus nerve at the ear can strengthen the communication between stomach and brain within minutes. The study results are currently published in the renowned journal Brain Stimulation.
The vagus nerve is responsible for
controlling many aspects of human behavior: This cranial nerve connects several
important organ systems with the brain and thus supports the transmission of
endogenous signals. These help, for example, in the goal-directed search for
food by tuning the reward system for food stimuli when the stomach is empty.
Previous research showed that the vagus nerve can regulate digestion via the
brain. This mechanism is relevant for therapeutic applications because the
vagus nerve can be stimulated non-invasively. With a new study, the team of PhD
student Sophie Müller and Prof. Dr. Nils Kroemer addresses the previously
unanswered question of how exactly the modulation via the brain works.
About
the study
The team, consisting of scientists from
the universities of Tübingen and Bonn as well as the German Institute of Human
Nutrition in Potsdam and the German Center for Diabetes Research, studied a
total of 31 participants. They combined stimulation of the vagus nerve at the
ear with simultaneous recording of brain activation via functional magnetic
resonance imaging (MRI) and a so-called electrogastrogram. The
electrogastrogram involves placing electrodes – similar to an ECG – 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,” Prof.
Kroemer said. He leads a research group on the neurobiological basis of
motivation, action, and desire (neuroMADLAB) in the field of translational
psychiatry at the Department of Psychiatry and Psychotherapy at the University
Hospital of Tübingen and has been Professor of Medical Psychology at the
Department of Psychiatry and Psychotherapy at the University of Bonn since
2022.
The
study results at a glance
The research team stimulated both the
vagus nerve at the ear and, in a control condition, other nerves at the ear in
participants. “We observed that vagus nerve stimulation increased coupling with
signals from the stomach in the brainstem and midbrain,” explained Prof.
Kroemer, continuing, “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.” In addition, the researchers discovered that coupling
with the stomach increased throughout the brain, particularly in regions that
already communicate more strongly with the stomach before stimulation. Changes
in coupling between the stomach and brain can be produced almost
instantaneously and spread rapidly.
These findings may enable new therapeutic options. For example, Prof. Kroemer’s group is currently conducting further research into a possible application for depression, where changes in communication between the body and the brain are already considered a key factor. Likewise, in obesity and eating disorders, stimulation of the vagus nerve could help affected individuals to restore their perception of body signals in the future.
Source: https://www.medizin.uni-tuebingen.de/en-de/das-klinikum/pressemeldungen/518
Journal article: https://www.brainstimjrnl.com/article/S1935-861X(22)00197-8/fulltext
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