Neuroscientists have traced neural pathways that connect the brain to the stomach, providing a biological mechanism to explain how stress can foster ulcer development.
The findings, published in the Proceedings of the National Academy of Sciences, build a scientific basis for the brain's influence over organ function and emphasize the importance of the brain-body connection.
Until now, research exploring the gut-brain interaction has largely focused on the influence of the gut and its microbiome on the brain. But it's not a one-way street -- the brain also influences stomach function.
To find brain regions that control the gut, the researchers used a strain of rabies virus to track connections from the brain to the stomach.
After being injected into the stomach of a rat, the viral tracer made its way back to the brain by hopping from neuron to neuron -- using the same trick that rabies virus uses to infiltrate the brain after entering the body through a bite or scratch -- to reveal the brain areas that exert control over the stomach.
The authors found that the parasympathetic -- "rest and digest" -- nervous system pathways trace back from the stomach mostly to a brain region known as the rostral insula, which is responsible for visceral sensation and emotion regulation.
"The stomach sends sensory information to the cortex, which sends instructions back to the gut," the author said. "That means our 'gut feelings' are constructed not only from signals derived from the stomach, but also from all the other influences on the rostral insula, such as past experiences and contextual knowledge."
In contrast, the sympathetic -- "fight or flight" -- pathways of the central nervous system, which kick in when we're stressed, predominantly trace back from the stomach to the primary motor cortex, which is the seat of voluntary control over the skeletal muscles that move the body around.
Identifying these neural pathways that connect the brain and stomach could provide new insights into common gut disorders.
For example, Helicobacter pylori infection typically triggers ulcer formation, but descending signals from the cerebral cortex could influence the bacteria's growth by adjusting gastric secretions to make the stomach more or less hospitable to invaders.
These insights also could change clinical gastroenterology practice. Knowing that the brain exerts physical control over the gut gives doctors a new way to approach bowel problems.
"Several common gut disorders, such as dyspepsia or irritable bowel syndrome, might not get better with current treatments," said the author. "Our results provide cortical targets that will be critical for developing new brain-based therapies that might be helpful for our patients."
Multiple areas of the cerebral cortex influence the stomach
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