The Interoceptive Sense That Comes from Someone Else
“Our peripheral nervous system is made up of both fast, myelinated A fibers and slow, unmyelinated C fibers. These two systems serve very different roles. ”
There’s something I’ve been wanting to say about interoception—something that’s not only fascinating from a neuroscience perspective, but also kind of profound when you stop and think about what it says about us as human beings... and as massage therapists.
Our peripheral nervous system is made up of both fast, myelinated A fibers and slow, unmyelinated C fibers. These two systems serve very different roles.
The fast A fibers are used for all of our exteroceptive senses—vision, hearing, touch, proprioception—anything that helps us respond immediately and stay in sync with the external world. Makes sense, right? If something’s coming at you or you’re about to fall, you want your nervous system to react fast.
In contrast, interoception—the sense of what’s going on inside our body—uses slow, unmyelinated C fibers. And that makes sense too. There’s no need to know about your blood pressure or digestion with split-second timing. Those signals are more about general state regulation than pinpoint information.
So what you get is a pretty clean division: external senses = fast A fibers. Internal senses = slow C fibers.
But here’s where it gets cool.
Explore the neural mechanisms behind internal body awareness and discover how interoception influences emotion, decision-making, trauma, and social connection.
There’s one fascinating exception to this rule: the C-tactile fiber. These are unmyelinated C fibers—so, by definition, interoceptive. But they respond to a very particular kind of touch. Not just any touch—touch that is delivered slowly and gently, within a narrow speed range...basically, something like a classic effleurage stroke.
And because it’s a C fiber, the signal doesn’t go to the somatosensory cortex to tell you where you were touched. It goes to the insula and limbic system. Its job isn’t to locate the touch—it’s to let you feel the touch. Emotionally. It regulates. It soothes. It calms. It gives us that sense of “someone is here with me.”
So this is the wild part: this is the only interoceptive sensation we have that originates from something outside of us.
All our other interoceptive signals—hunger, heart rate, tension, nausea, fullness—are generated from inside. But C-tactile touch only comes from the outside... and it only comes from another human being who is close enough and caring enough to offer that touch.
Final Thoughts
What an extraordinary evolutionary detail. This entire system exists to support one thing: co-regulation. We are wired to need one another.
And as massage therapists, we are the only profession that gets to work with this very special system—consciously and deliberately. We get to activate a pathway that wasn’t designed for information or analysis, but for comfort and connection. That’s not just meaningful—it’s beautiful.
Massage therapy doesn’t just feel good. It taps into one of the deepest biological truths of our species: that we were never meant to do this alone.
Author
Dr. Mark Olson holds an M.A. in Education and a Ph.D. in Neuroscience from the University of Illinois, specializing in Cognitive and Behavioral Neuropsychology and Neuroanatomy. His research focused on memory, attention, eye movements, and aesthetic preferences. Dr. Olson is also a NARM® practitioner, aquatic therapist, and published author on chronic pain and trauma-informed care. He offers a variety of courses at Dr-Olson.com that provide neuroscientific insights into the human experience and relational skill training for professionals and curious laypersons.
