Introducing the brain: interoception (Introduction)

by David Turell , Thursday, May 16, 2024, 20:37 (39 days ago) @ David Turell

Sensing our organs internally:

https://www.sciencenews.org/article/heart-brain-mental-health

"Powerful signals travel from the heart to the brain, affecting our perceptions, decisions and mental health. And the heart is not alone in talking back. Other organs also send mysterious signals to the brain in ways that scientists are just beginning to tease apart.

"A bodywide perspective that seeks to understand our biology and behavior is relatively new, leaving lots of big, basic questions. The complexities of brain-body interactions are “only matched by our ignorance of their organization,” says Peter Strick, a neuroscientist at the University of Pittsburgh.

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"Coalitions of cells in the brain exert exquisite control over the heart. In some parts of the brain, more than 1 in 3 nerve cells influence the heart’s rhythm, Tallon-Baudry and her colleagues reported in 2019 in the Journal of Neuroscience. One of these brain regions, the entorhinal cortex, is famous for its role in memory and navigation. It makes sense that these two jobs — physically moving through the world and influencing heart rate — would fall to the same neurons; the tasks of seeing a jogging path and priming the heart for running are linked.

"The brain bosses the heart around. But that’s not the whole story — not even close. Scientists are finding that information from the heart can boss around our brains and our behavior, too.

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"These results and others suggest the tantalizing possibility that our brains are taking in and using information from the heart — and perhaps other interoceptive awareness — to help us make sense of the world. But findings from people are often correlational. It’s been hard to know whether beating hearts caused the effects or whether they just happened at the same time.

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"...experiments turned up a key player in the brain: the insula. The human insula, one on each side of the brain, has been shown to have a role in emotions, internal sensations and pain. Shutting down neuron activity in the mice’s insula silenced the racing heart’s influence on behavior, the team found.

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"...what Strick and colleagues have done with various organs — stomach and kidney, for instance — and the brain. Some of the most tantalizing connections he has found are between the adrenal glands, which pump out fight-or-flight hormones in an emergency, and specific brain regions, especially neural locales that control muscles.

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"...Perhaps, she thought, the neurons were sensing the pressure caused by the pump directly.

"This direct sensing is a cellular possibility. In 2021, neuroscientist Ardem Patapoutian, a Howard Hughes Medical Institute Investigator at Scripps Research in La Jolla, Calif., had received a Nobel Prize for the discovery of mechanical sensors called PIEZO1 and PIEZO2, present in many animals including humans. These sensors, which sit in cell membranes and look like three-bladed propellers, can detect pressure changes, including the inflating of lungs that comes after a deep breath, the stretch of a full bladder and the pressure of blood moving through a vessel.

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"Understanding interoception may yield insights that go beyond alleviating anxiety. Some scientists, including Tallon-Baudry, suspect that signals from inside our bodies collectively help give rise to consciousness. The concept that consciousness requires a body that can be sensed and an organism striving to stay alive isn’t new, but recent interoception results have added evidence to support the idea that the body’s drive to monitor itself may be more important than previously thought.

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"Interoceptive signals, and not just those from the heart, but also from the lungs, stomach, muscles, skin and more, may help create a person’s sense of self — their “I,” their identity as a conscious, aware entity with a point of view. Tallon-Baudry and colleagues described last year in Nature Neuroscience how rhythmic signals from the heart, the lungs and the stomach all converge in the brain. That review also advanced the idea that a sense of self relies on internal body signals.

Comment: this area of research is very new and reeks of purposeful design. We are very aware of our organs functioning. We breath, we urinate, we defecate, and, in a startle, we feel our heart pound. The brain keeps strict contact with every internal function. But it is a two-way setup with influences in both directions.