You mentioned that the brain integrates past experiences into the experience of pain. Can you elaborate on what you mean by that and what an example looks like?
So a lot of times the signal that arrives there when you have let's say an "active pain stimulus" or a signal that causes injury like an inflamed knee in osteoarthritis. Or maybe you hurt yourself, that is a signal of nociception that comes through. But when the signal arrives at the brain, the brain has to have this complicated, really fast network of circuits that are already there.
It has to decide is this swelling or something that I'm feeling in the back? Or the knee? Is it something that I felt before? Where am I when the thing has happened? If I was in the middle of a busy road, but I also had my child with me then it would decide that the bigger problem is not me, but it is of getting the child and oneself to safety. It would give that a preference. But if it were in your home, and you felt the same signal then all the attention is then paid to why is that happening? Did that same swelling happen before what did I do when the swelling happened at that time? Did I tighten the muscles around the knee did I straighten it, or did I go down and lie down?
Whatever it felt was the appropriate response that guaranteed safety the last time around, it would then have the same circuit as a quick shortcut to execute. Because the brain at the end likes to convenience and likes to do familiar things quickly and efficiently.
So most of these signals and chemicals that arrive, will have already have a predicted response that the brain would do in terms of safety. But if a new response were to arrive, it hasn’t felt it before, that’s where the errors come along. That's where it would say “well, I don't know what to do but I haven't felt this before, but the closest similar thing that I had was this experience when it was in the knee. And the problem may not be in the knee. Might being the ankle, it might be in the thigh”.
But they would rather execute the same familiar response for safety, based on its previous experience. But it doesn't get the error in the prediction. It is predicted that the problem is around the knee, but the problem may be elsewhere but executes the same problem.
I see this clinically in patients with chronic back pain. The first time they had the episode of back pain might have been due to maybe a slipped disc. So when back pain becomes chronic and becomes persistent, then it becomes a habit that the brain has picked up. And it executes the same loop of protecting and tightening the muscle spasm, repeated sciatica but then when we do MRI scans, or when we check it out again there's nothing on the scan to be found.
Patients are surprised, saying “why am I getting that”? And this is an example of where there is no nociception but the experience of pain is very real because the brains acting out based on previous experience.
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