How getting bitten by a crab taught me about functional conditions
Post 11
There was a time when a crab had just bitten me on the leg. There I was, standing at the lectern in front of about 200 doctors, giving a talk on a subject that I really didn't know very well. I was halfway through the presentation when I felt the claws of a large crab grip my thigh in its pincers. I even knew what the crab looked like. It was large and red, just like the one that had startled me as a child. While continuing the lecture, I reflexively moved my hand down to flick the crab off my thigh. To my surprise, there was no crab, nor anything else - just my leg. I nearly burst out laughing that my body had revealed how stressed I was, even though I would have claimed to have been reasonably calm. The 'crab' was just my thigh muscles tensing into a cramp. They were sending me a message, 'You're in danger here! Run for your life!' The fight or flight response was in full swing, while I was calmly blithering on to the doctors.
All the while continuing the talk, I secretly marvelled that I could seem that I was calm giving the lecture, but my body was picking up the stress signals that my mind needed to ignore during the talk.
Later, I reflected on this unusual experience: not only had I just had a totally convincing sensation on the pincers of a crab trying to pierce my skin, but I had further ‘confirmation’ with a clear image of the crab, which was about a foot across and red. My reflex to flick the crab away was instantaneous.
Each of these experiences reinforced my conviction that there really was a crab on my leg. The fact that I was not in the water or even a seafood market, but an inland lecture theatre did not in that instant affect my belief. It was that real.
Where did the image of the red crab come from? I knew instantaneously that it was the crab that had startled me as a 10 year old trying on some new goggles for the first time and bending to look at my feet in the water I was standing in. I saw not just my feet in the sand but a large red crab advancing towards them. I was able to leap out of the water, returning with a net to catch the creature. This childhood memory was deeply buried until I was experiencing perhaps a similar level of stress.
The experience taught me that the mind can interpret an experience in a very convincing way: in the split second when I felt the ‘bite’, there was no way I would have believed it was really a muscle cramp. It felt like a bite. So, I have personal experience similar to when my patients say to me, ”I know my body.” It is sometimes very hard to convince people that their mind’s capacity to interpret a physical sensation erroneously may be the reason for their belief that they have a physical condition: it feels just like it.
Because of this bizarre and powerful experience, I became curious about exactly what had happened to me and why do some people experience symptoms which can be more persistent, frightening, and disruptive. How, under certain circumstances, do humans have symptoms that seem to arise spontaneously and take on a meaning with great force, despite there being no obvious cause?
My research led me to the neurologists who have been using functional MRIs to understand how the brain creates these errors. They have put forward the Predictive Processing Model, which is how the research into functional symptoms explains the error.
What is the Predictive Processing Model and how does it relate to functional symptoms?
When I first studied neurology in the 1970s, the brain was understood to be like a machine: you feed in a stimulus, and you get a response. A more accurate understanding of the brain needs to include the Predictive Processing Model. Over our lifetime, we learn to expect certain experiences and react automatically with a response that our subconscious has predicted to be best.
Imagine if you burnt your lips every time you drank a hot drink. This is what would happen if you didn’t utilise automatically your capacity for Predictive Processing. The model explains how our subconscious holds memories of past experiences and tries to predict any new encounter to anticipate the best response. For example, without thinking, we always sip a hot drink to gauge how to avoid burnt lips or we might automatically duck if we hear a loud sound. The model hypothesises that you might get struck by a flying object. All good so far.
But what if our minds propose the wrong prediction? In my case, the model produced a crab as the reason my leg felt a sharp sensation. My subconscious held the idea of a crab bite, and, rather ridiculously, proposed it as the reason.
Is this what happened when my patient, Win, insisted she had a bladder infection, even though the tests were completely clear? Her brain produced this explanation for her symptoms because she had experienced infections in the past. I could believe her when she said it felt just like previous infections. But it was an error in her predictive processing. *
The lack of understanding of the Predictive Processing Model is one of the reasons people might struggle to accept that their symptoms are functional. They trust what their body is telling them. This is understandable, but unfortunately, relying on what your brain might be saying can be wrong.
If you are living with ongoing symptoms, your mind may have retained some stories about your symptoms. Gaining a better understanding of how your Predictive Processing may be giving you unhelpful messages is a useful step towards your recovery.
My book does briefly discuss this phenomenon, but you may find it helpful to research some of the links below which give a further explanation.
https://www.youtube.com/watch?v=aXvR9zXpsYg
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.fndaction.org.uk/wp-content/uploads/2022/10/Information-guideance-for-medical-professionals.pdf
Some of these sites are very technical so you can share them with your doctor if you think Predictive Processing problems may be relevant to you.
Wishing you all the best.
*In Part 3, I describe how such persistent symptoms can be treated not by antibiotics but by physiotherapy.