Introducing the brain: sensing autonomic activity (Introduction)

by David Turell , Monday, November 08, 2021, 18:33 (892 days ago) @ David Turell

This is no surprise to me:

https://www.quantamagazine.org/new-science-shows-immune-memory-in-the-brain-20211108/

"...in a paper published today in Cell, the neuroimmunologist Asya Rolls has shown that a similar kind of conditioning extends to immune responses. Using state-of-the-art genetic tools in mice, her team at the Technion in Haifa, Israel, identified brain neurons that became active during experimentally induced inflammation in the abdomen. Later, the researchers showed that restimulating those neurons could trigger the same types of inflammation again.

***

"In recent years Rolls’ lab has begun to get a handle on how thoughts and emotions could affect physical health. In 2018, she and her co-workers reported that stimulating neurons in the brain’s pleasure centers in mice disabled a subset of immune cells that suppress the body’s defenses; tumor growth slowed in those animals. In a study published in May, her team found that activating specific nerves in the colon prevented immune cells in the blood from entering the tissue — offering a mechanism for brain control over local inflammation.

"Given that these groups of neurons regulated immune activity with such precision, Rolls couldn’t imagine that the brain would control a system without knowing its status. “So we wanted to see how the brain represents the state of the immune system,” she said.

***

"The immune responses sparked by neural stimulation “were reminiscent of the original” disease state, Rolls said. The similarities extended to the molecular level: In the mice with induced peritonitis, white blood cells carrying a specific receptor protein became more abundant in the abdominal lining during both the original inflammation and the inflammation evoked later.

"The researchers also observed the opposite effect: When they instead inhibited the initial set of activated neurons, the animals’ disease symptoms weren’t as severe. This suggests that even during chemically induced inflammation, signals from the brain may be helping to determine its severity.

"In a set of nerve-mapping experiments, the team determined that the insula neurons that kicked into action during the initial inflammation in fact “have a way to deliver a message all the way to the colon,” Rolls said.

"In Tracey’s view, the new research shows “you can’t separate the state of the neuron activity from the state of the immune system activity. It’s a two-way street.”

***

"Unlike the vagal nerve system, however, the insula neurons in Rolls’ mechanism sense the inflammation, remember that immune state and can reactivate it — a behavior that is more like Pavlovian conditioning than a negative feedback response, Medzhitov said. Tracey thinks of it this way: The vagus nerve is like a brake line in a car. Rolls’ study shows “there is a driver,” he said. “There is someone who decides whether to hit the brake or the gas pedal.”

***

"However, as Rolls and her colleagues noted in their paper, they cannot yet say whether the insula neurons’ “memory” of the inflammation in some way describes the immune response itself, or if it’s instead a record of the sensations from the inflamed body tissues — in effect, the memory of what it felt like to be sick with that inflammation. They also can’t rule out that other parts of the brain could be involved in remembering the immune response too. What the study does show is that “this information is encoded even though it may not be consciously experienced,” said Medzhitov.

"The new findings also upend the common top-down view of the brain. “Most people tend to think, ‘We’re so smart, we decide what to do,’ and then we make our body do it,” Tracey said. “But that’s not how the nervous system works.” Instead, the brain receives and synthesizes information about changes in the body — an infection, a fever — and delivers a response.

"Rolls’ work shows that “the brain is inseparable from the immune system,” said Tracey. “I think immunologists and neuroscientists both are going to be excited and surprised.'”

Comment: the autonomic system runs body processes automatically, but this shows the brain keeps track of it all and can modulate responses. A very neat design. We are busy with our own external affairs, so our internal affairs need to run on their own, but have a backup the brain keeps and automatic eye on what's happening and avoid overreactions. Not by chance.