Introducing the brain: vagus nerve interoception (Introduction)

by David Turell , Friday, June 11, 2021, 19:05 (1042 days ago) @ David Turell

How we sense our internal organs. The vagus nerve is very busy:

https://www.sciencemag.org/news/2021/06/newly-detailed-nerve-links-between-brain-and-ot...

"scientists are starting to unravel how our wet, spongy, slippery organs talk to the brain and how the brain talks back. That two-way communication, known as interoception, encompasses a complex, bodywide system of nerves and hormones. Much recent exploration has focused on the vagus nerve: a massive, meandering network of more than 100,000 fibers that travel from nearly every internal organ to the base of the brain and back again.

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"As part of the parasympathetic nervous system—active when the body is at ease or recovering from stress—the vagus regulates autonomic functions such as heart rate, breathing, and digestion. But new studies have shown signals carried by vagal fibers climb beyond the brainstem, revealing a broad interoceptive network in the brain that interprets internal changes, anticipates the body’s needs, and sends commands to fulfill them. The network includes brain regions involved in more complex cognition, which means the nerves monitoring the body’s basic workings also respond to—and influence—how we remember, process emotion, and even construct our sense of self.

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"Single-cell RNA sequencing, which allows scientists to identify cell types within a tissue on the basis of their patterns of gene expression, has at last made it possible to dissect the “dark matter of the vagus,” says Steve Liberles, a cell biologist at Harvard Medical School. His team used genetics to identify a “staggering diversity” of vagal cell types in rodents, including cells that control breathing and trigger cough, sense changes in blood pressure and oxygen, and detect stretching and nutrients in the digestive system. Most recently, Liberles’s team discovered cells in the brainstem, connected to vagal neurons, that trigger nausea.

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"Peter Strick, a neuroscientist at the University of Pittsburgh, injected the virus into rat stomachs and discovered vagal pathways that lead to the rostral insula, a poorly understood region thought to process sensations from internal organs and regulate emotions. Strick later showed that those insula cells stimulate digestion, whereas a second vagus tract extending from the motor cortex to the stomach does the opposite—arresting acid production and muscle contractions that help digest and move food.

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"Rather than passively receiving information, the brain is constantly constructing a model of its sensory conditions and guessing what caused them in order to direct the correct response, Barrett says. “You feel a tug in your chest, and your brain has to decide if it’s because you ate too much for dinner or if it’s the early sign of a heart attack.”

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"To Tallon-Baudry, the research in coma patients challenges a long history of thinking of bodily regulation as separate from “higher” mental processes, such as language, that constitute our sense of self. Four centuries ago, René Descartes famously conceptualized the mind as being separate from the body. But the EEG study, she says, offers a different idea of consciousness, as a subtle and private act of interoception: “just being present, as the subject of experience.”

Comment: Part of our conscious awareness is the way we sense our bodily functions primarily through the vagus nerve, one of 12 cranial nerves that connect directly to the brain for interpretation. We are the only organism that can make those interpretations. For example, the vagus nerve makes the ape vomit, but only we wonder why. Currently I'm having a mild GI upset and so is my dog. I'm assuming we both have the same virus. These nerve connections let us live while the body primarily runs itself. The system is called the autonomic nervous system. This article is massive and describes many studies using vagus stimulation for various ameliorative purposes. A great design, very coordinated, requiring a designer mind.