Fibromyalgia and ME/CFS: an interoceptive predictive coding model of pain and fatigue expression, 2021, Sharp et al

[Grigor]

1. Harriet Sharp1,2,
2. Kristy Themelis1,3,
3. Marisa Amato1,
4. Andrew Barritt1,
5. Kevin Davies1,
6. Neil Harrison1,4,
7. Sarah Garfinkel1,5,
8. Hugo Critchley1,2,
9. Jessica Eccles1,2

Abstract:

Introduction: The aetiology and pathophysiology of fibromyalgia and ME/CFS are poorly characterised but altered inflammatory, autonomic and interoceptive processes have been implicated. Interoception has been conceptualised as a predictive coding process; where top-down prediction signals compare to bottom-up afferents, resulting in prediction error signals indicating mismatch between expected and actual bodily states. Chronic dyshomeostasis and elevated interoceptive prediction error signals have been theorised to contribute to the expression of pain and fatigue in fibromyalgia and ME/CFS.

Objectives/Aims: To investigate how altered interoception and prediction error relates to baseline expression of pain and fatigue in fibromyalgia and ME/CFS and in response to an inflammatory challenge.

Methods: Sixty-five patients with fibromyalgia and/or ME/CFS diagnosis and 26 matched controls underwent baseline assessment: self-report questionnaires assessing subjective pain and fatigue and objective measurements of pressure-pain thresholds. Participants received injections of typhoid (inflammatory challenge) or saline (placebo) in a randomised, double-blind, crossover design, then completed heartbeat tracking task (assessing interoceptive accuracy). Porges Body Questionnaire assessed interoceptive sensibility. Interoceptive prediction error (IPE) was calculated as discrepancy between objective accuracy and subjective sensibility.

Results: Patients with fibromyalgia and ME/CFS had significantly higher IPE (suggesting tendency to over-estimate interoceptive ability) and interoceptive sensibility, despite no differences in interoceptive accuracy. IPE and sensibility correlated positively with all self-report fatigue and pain measures, and negatively with pain thresholds. Following inflammatory challenge, IPE correlated negatively with the mismatch between subjective and objective measures of pain induced by inflammation.

Conclusions: This is the first study to reveal altered interoception processes in patients with fibromyalgia and ME/CFS, who are known to have dysregulated autonomic function. Notably, we found elevated IPE in patients, correlating with their subjective experiences of pain and fatigue. We hypothesise a predictive coding model, where mismatch between expected and actual internal bodily states (linked to autonomic dysregulation) results in prediction error signalling which could be metacognitively interpreted as chronic pain and fatigue. Our results demonstrate potential for further exploration of interoceptive processing in patients with fibromyalgia and ME/CFS, aiding understanding of these poorly defined conditions and providing potential new targets for diagnostic and therapeutic intervention.

https://jnnp.bmj.com/content/92/8/A3.3

 

[Hoopoe]

Why would one assume that the ability of patients to accurately count their heart beats tells us anything about the cause of pain and fatigue?

When I count my heart beat, I rely on touch and sound. It doesn't seem likely that the relevant portions of the brain also rely on touch and sound.

 

[shak8]

What is this computer-jargon have to do with the not well-elucidated brain modulatory process, and call it top-down prediction signals when obviously in fibromyalgia, the huge amount of sensory (afferent) nerve input to the brain is off the charts?

"Interoception has been conceptualised as a predictive coding process; where top-down prediction signals thcompare to bottom-up afferents, resulting in prediction error signals indicating mismatch between expected and actual bodily states. Chronic dyshomeostasis and elevated interoceptive prediction error signals have been theorised to contribute to the expression of pain and fatigue in fibromyalgia and ME/CFS..."

This is just so much fluff.

 

[Hutan]

I'll be interested to read this if it becomes accessible. Where are the stats?

I had hoped Neil Harrison would get over his involvement with people pushing this idea and go and do something useful. But it seems he hasn't.

I note that all of the authors have an association with the Brighton and Sussex Medical School. I guess there are plenty of BPS guest lecturers in that part of the world.

The conclusion is: you can't believe what these people (probably mostly women) report about their bodies, because they are prone to exaggerating normal body sensations as something pathological.

I think they asked people to predict their heart rate, or something like that, something called a 'heart beat tracking task'. Turns out that everyone, with or without ME/CFs and FM were equally bad at it.

no differences in interoceptive accuracy

They asked people to fill out a survey called the Porges Body Questionnaire. I don't know what version they used, but here's the short form. It has two parts: body awareness; and Autonomic Nervous System Reactivity. I'm guessing they just used the 'Body Awareness' part.

I. Body awareness
Please rate your awareness on each of the characteristics described below. Select the answer that most accurately describes you.

During most situations I am aware of:

(The scale is Never, Occasionally, Sometimes, Usually, Always)
1. Swallowing frequently
2. An urge to clear my throat
3. My mouth being dry
4. How fast am I breathing
5. Watering or tearing of my eyes
6. Noises associated with my digestion
7. A swelling of my body or parts of my body
8. An urge to defecate
9. Muscle tension in my arms and legs
10. A bloated feeling because of water retention
11. Muscle tension in my face
12. Goose bumps
13. Stomach and gut pains
14. Stomach distension and bloatedness
15. Palms sweating
16. Sweat on my forehead
17. Tremor in my lips
18. Sweat in my armpits
19. The temperature of my face (especially my ears)
20. Grinding my teeth
21. General jitteriness
22. The hair on the back of my neck standing up
23. Difficulty in focusing
24. An urge to swallow
25. How hard my heart is beating
26. Feeling constipated

The Body Awareness questionnaire is claimed to be "A measure of sensitivity for internal bodily functions. Values at the high end of the scale reflect hypersensitivity and values at the low scale reflect hyposensitivity."

I find the question very ambiguous. Does 'during most situations I am aware of' mean 'under most circumstances, I would be aware if, for example, I had an urge to swallow'? Or, 'most of the time I have an urge to swallow'?. I presume the correct interpretation must be 'how often are you aware of this'? But then what is the 'During most situations' doing there?

But anyway, the authors of this paper are suggesting that people with ME/CFS and FM scored higher than the controls, and that this suggests that the people with ME/CFS and FM think they have a high sensitivity to their body's function.

I question whether the Porges questionnaire really does measure body awareness. Being aware of feeling constipated or stomach and gut pains doesn't have to have anything to do with overall body awareness - it just might mean you have a gut issue. Being aware of a difficulty focusing might just mean that you need glasses, or it might be a symptom of ME/CFS. A bloated feeling because of water retention might just indicate you are female of reproductive age. Sweat on your forehead might indicate you live in a hot country, or regularly go jogging.

But, even if it does measure some aspects of body awareness, the score has little to do with how good you think you are at knowing what your heart rate is. The whole premise of this paper makes no sense to me. At all. It seems to me that it is a nasty piece of misogeny.

I'll be interested in your thoughts. Maybe I have misunderstood it.

 

[rvallee]

Conclusions: This is the first study to reveal altered interoception processes in patients with fibromyalgia and ME/CFS

The aetiology and pathophysiology of fibromyalgia and ME/CFS are poorly characterised but altered inflammatory, autonomic and interoceptive processes have been implicated

If this is the first, how can the introduction list it as having "been implicated"? If this is the first, the citation for the presence of "altered interoception" would be... itself. It's a recursive citation. Because this whole field is a parody of bad science.

And many things have been conceptualized, it literally means nothing. Cthulhu has been conceptualized. What a bunch of juvenile nonsense.

 

[MEMarge]

I had hoped Neil Harrison would get over his involvement with people pushing this idea and go and do something useful. But it seems he hasn't.

He has moved to Cardiff Uni.
He spoke at an AfME AGM where he was showing slides of brain activity. (Do not have notes to hand re type of imaging etc). I chatted with him afterwards, briefly before he left for his train, as he spoke of increased activity in the basal ganglia.
My daughter was found to have autoantibodies to the pyruvate kinase receptors in the basal ganglia. He was surprised that I'd noticed that only one of the basal ganglia showed this effect, but did not know why this had occurred.

 

[Hutan]

My daughter was found to have autoantibodies to the pyruvate kinase receptors in the basal ganglia. He was surprised that I'd noticed that only one of the basal ganglia showed this effect, but did not know why this had occurred.

That sounds important MEMarge. Do we have a thread discussing that in general terms? e.g. who was doing the finding of such autoantibodies?