Interoception: the Sense of How You Feel Inside

A recent article in Tech Review, https://www.technologyreview.com/2026/06/12/1138833/inside-interoception-brain-body or: https://archive.is/kGwUQ
discusses new work on understanding the data that the body sends to the brain--and it's a lot more than was commonly thought...

Our senses take in information at a staggering rate-roughly 11 million bits flood in every second from our skin, eyes, ears, and more. [...] Only a sliver reaches our conscious awareness. Researchers estimate that our conscious minds can process roughly 10 to 60 bits of information per second, about the rate at which you're reading this sentence. That's a ratio of about one conscious bit to hundreds of thousands of unconscious bits.
[...]
What you are aware of: Your stomach growling when you're hungry. Your palms sweating before you speak in public. The breath you just took, if you pay attention to it. Even your heartbeat, which some people can sense from the inside without feeling their pulse in their wrist.
Scientists have a word for how we sense ourselves from the inside: interoception.

After a page or so of discussion about different signal types that are now being mapped, the article switches to developing an understanding how the sensing is done. In particular the sense of physical force or pressure--

In the 1990s, as a postdoc at the University of California, San Francisco, he [Ardem Patapoutian] became fascinated with our sense of touch-the last of the five major senses not yet understood at the molecular level. The lung stretch signal that Liberles's vagus neurons [discussed in the link] carry to the brain? No one had ever figured out how that signal began.
"How do you feel the embrace of a loved one? How do your fingers distinguish one texture of hair from another?" Patapoutian invites us to wonder in his 2021 Nobel Prize lecture. The problem: Most cellular communication works through chemistry. But mechanical force offers no molecule to bind. How does the body translate physical pressure into the electrochemical language that neurons speak?
Scientists knew that the answer had to be an ion channel-a protein gate embedded in cell membranes that opens to let electrically charged particles into the cell. But tracking down the one responsible for touch turned out to be absurdly difficult. Ion channels are a hundred thousandth the size of a cell, invisible to ordinary microscopes. Worse, they don't resemble each other. You can't recognize one by its shape or its sequence of amino acids. Even with one right in front of you, nothing would tell you it was there.
[...] Patapoutian decided to try an unusual approach. He'd try to find cells that showed sensitivity to touch and destroy their internal genetic blueprint one gene at a time-hunting for the move that would make the cell go numb. It was tedious, expensive, and possibly a dead end. "A lot of people made fun of us," he says.

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