Melzack and Katz: Part 6e: Ref 4. Pattern theories in History of Pain

The paper, Pain.

Part 1 First two sentences

Part 2 Pain is personal Also Pain is Personal addendum., Neurotags! Pain is Personal, Always.

Part 3a Pain is more than sensation: Backdrop

Part 3b Pain is not receptor stimulation

Part 3c: Pain depends on everything ever experienced by an individual

Part 4: Pain is a multidimensional experience across time

Part 5: Pain and purpose

Part 6a: Descartes and his era; Part 6b: History of pain - what’s in “Ref 4”?; Part 6c: History of pain, Ref 4, cont.. : There is no pain matrix, only a neuromatrix; 

Part 6d: History of Pain: Final takedown

PATTERN THEORIES

Today, we are still examining the chapter in Challenge of Pain by Melzack and Wall, "Ref. 4" in the new paper, Pain, by Melzack and Katz, in the slow meander through it. (Yes.. some day, we'll arrive back into the paper itself and it will be as though we had never wandered away from it in the first place.)

Anyway: on page 157, we see this:

"As a reaction against the psychological assumption in specificity theory, other theories have been proposed which can be grouped under the general heading of "pattern theory.""

[Melzack is pretty adamant that there be no psychological assumptions, ever.]

SYPHILIS!

The earliest pattern theory developed from Goldscheider (1894), who at first nodded along with von Frey, but later wondered if stimulus intensity and central summation might have anything to do with anything. According to Melzack and Wall he looked carefully at studies of pathological pain, e.g., Naunyn's study in 1889 on tabes dorsalis of late stage syphilis. (See "intensive theory"in wikipedia). Noordenbos in 1959 pointed out that in tabes dorsalis, one of the big symptoms is temporal and spatial summation of input, resulting in pain.

"Successive, brief applications of a warm test tube to the skin of a tabetic patient are at first felt only as warm, but then increasingly hot until the patient cries out in pain as though his skin is being burned." p. 157

Single pinpricks evoke "diffuse, prolonged, burning pain" in someone with tabes. And a pinprick may be felt, but not until as many as 45 seconds later!

Source
Let's hear it again for penicillin!
It made syphilis go away for a long long time,
although it has crept back lately.

Anyway, thoughtful people wondered about this kind of presentation. They thought, hmmn.. no.... there is more to sensation and pain perception than just a bunch of wires all hooked up.

"Goldscheider.. was compelled to conclude that mechanisms of central summation, probably in the dorsal horns of the spinal cord, were essential for any understanding of pain mechanisms. The long delays and persistent pain observed in pathological pain states, Goldscheider assumed, are due to abnormally long time-periods of summation." p. 158

All other pattern theories derive from Goldsheiber's early recognition that there had to be more going on than met the eye.

1. Peripheral pattern theory: Weddell 1955; Sinclair 1955

• pain thought to be due to excessive peripheral stimulation
• still bottom-up
• theory proposes that all fibre endings (except those found innervating hair cells, in the inner ear I presume) are alike
• however there is actually quite a lot of receptor specialization, which undermines the theory

2. Central summation theory: Livingston 1943

• was the first to suggest that remarkable summation phenomena must have a basis in the CNS
• he conceived of "reverberatory circuits (closed, self-exciting loops of neurons)" existing inside the spinal cord
• these could be "triggered by normally non-noxious inputs which would be interpreted centrally as pain"
• this idea is useful for explaining phantom limb pain, sweating and jerking of stump
• no physiological evidence for functional reverberatory circuits was ever found
• this theory had an impact however

3. Sensory interaction theory

• specialized input controlling system normally prevents summation from occurring: if it's destroyed, pathological pain states follow
• Head, 1920: epicritic and protopathic
• Bishop 1946: fast and slow
• Noordenbos 1959: myelinated and unmyelinated
• fast system usually dominates the slow one: if it fails to do so, the result is protopathic sensation (Head), slow (diffuse, burning) pain (Bishop), or hyperalgesia (Noordenbos)
• Noordenbos' ideas caught on; idea of a multi-synaptic afferent system in spinal cord contrasts markedly to the idea of a straight-through system, might explain why cordotomy can fail to abolish pain - unless the whole spinal cord is cut, afferent input will find a way in

4. Affect theory

• older theory (Aristotle) considered pain to be an emotion, opposite pleasure, not a sensation
• Dallenbach 1939: Von Frey and Goldsheider were battling bitterly about it, and a third figure turned up, H.R. Marshall, who said, "Stop - you're both wrong. Pain is an emotional quality, a quale." 
• meanwhile progress galloped on and researching 'pain as sensation' gained so much traction that 'pain as affective or motivational' was left behind,  lumped under "reactions to pain" instead of being treated as part of its formation

.................

Next: Evaluation of theories (Hint: they all have something important to contribute)

Neurotags! "Pain is personal" always

This post is a departure from, but still related to, the series I'm heavily into writing just now, inspired  by Melzack and Katz. It echoes a post from that series, however, Melzack and Katz Pain2013 Part 2: Pain is personal.  I've been reflecting on the Moseley encounter from last Monday, as well, which gave me reason to sidetrack off into three posts (the link goes to the third, and the other two are linked inside it).  

Anyway, this morning Matthew Rupiper posted this video to somasimple, Ramon Ortiz, pitcher for the Toronto Blue Jays, injuring his elbow. 

Recall the Kevin Ware injury [graphic warning].

Recall the crowd's reaction, and the reactions of his teammates.

Recall his own retroactive reaction. 

"I didn't feel any pain. It didn't hurt. Honestly, it didn't hurt. It was just scary. It was probably one of the scariest moments in my life." 

Kevin Ware couldn't get up. His leg was dangling and a bone was sticking out. It was an obvious injury with blood loss. His teammates and the crowd felt for him. They expressed anguish openly on his behalf. I think this may have let him off the hook, somehow, psychosocially. 

By contrast, Ramon Ortiz felt something, terribly wrong.  

Ramon Ortiz right about 20 seconds
 after injuring his right elbow pitching

Only he could feel it. There was no obvious injury - no blood, no bone sticking out - his arm didn't break, he could move it after; he experienced a lot of apparent turmoil over it, it forced him into a corner where he couldn't continue to play, he became very emotional over it. Angry. Teary. He was the only one who could experience the situation. It affected him, and only him, in the moment. He carried this injury all by himself. 

He must have felt alone, as he felt it, alone. 

There is this whole social, interactive side to it - no one else could "feel" him "feeling" this ... elbow. 
So, even though his teammates gathered around, he looked like he was lost deep inside himself somewhere, processing, not really interacting with them. 

Now, I wonder which of these players, Ware or Ortiz, will carry the most enduring neurotag, for pain, in the future? 

Bones heal, especially in 20-something-year-old athletes. People rally round and provide massive support. The crowd gasps and teammates fall over in shock and horror and the injured player can perceive the empathic support: external psychosocial context in this case was a mirror and a buffer and a blotter, all at the same time. 

I would lay odds Ware will probably go back to inhabiting the same sense of self he did prior to injury. His neurotag may be minor, and he may be able to successfully disregard it.

In 40-year-old ball players who don't have blood loss or a bone sticking out, whose context includes a crowd just waiting for a sign his career is drawing to a close, and who can't really see what's going on, an injury might well feel like death, for the athlete part of the self; mourning may be involved, the exhausting prospect of having to reinvent oneself as a baseball non-player may instantly loom. 

I would lay odds that this guy's neurotag will have soaked into more of his brain and will be sticking, like velcro, like duct tape, to a whole lot more of his sense of self, to a whole lot more of his future.
Not that he can't overcome the physical pain of it all after a good night's sleep and a few days of good treatment and recuperation.. but I bet the pain neurotag of the injury itself will be more easily reactivated by context than Ware's will. 

A further thought:

I think a difference in future neurotag stickiness might have something to do with the degree of humiliation felt, regardless of whether it arrives as experienced from the outside or the inside of a sense of self.

Maybe we could figure out a formula: PainNeurotag subsequent to an injury (any kind) will be a function of the degree of momentary disablement, multiplied by amount of perceived humiliation or personal defeat associated with the disablement. Something like that.

If the crowd can absorb the angst of the moment, effortlessly and appropriately (the way it did with Ware), then less humiliation will be a future cling-on neurotag factor. If the crowd can't, if it distances itself, however carefully and politely, then there may be more.

Something like that.

(This idea needs way more work, I realize...)

Melzack and Katz: Part 6d. Ref 4. Final takedown

The paper, Pain.

Part 1 First two sentences

Part 2 Pain is personal

Part 3a Pain is more than sensation: Backdrop

Part 3b Pain is not receptor stimulation

Part 3c: Pain depends on everything ever experienced by an individual

Part 4: Pain is a multidimensional experience across time

Part 5: Pain and purpose

Part 6a: Descartes and his era

Part 6b: History of pain - what’s in “Ref 4”?

Part 6c: History of pain, Ref 4, cont.. : There is no pain matrix, only a neuromatrix

Continuing on from where we left off yesterday in "Reference 4", which is the history of pain section in Melzack and Wall's book, Challenge of Pain, first published in 1982:

Does any psychological evidence exist?

They point out there is no evidence, not one scrap, for there being any one-to-one correspondence between pain perception and stimulus intensity.

"Instead, the evidence suggests that the amount and quality of perceived pain are determined by many psychological variables in addition to sensory input."

Pavlov and his dogs. Think about those for a minute (Pavlov 1927). Pavlov fed the dogs and rang a bell; he conditioned the dogs to salivate when he only rang a bell. 

He did a lot more than that, apparently - he provided them with shocks, burns, cuts. As long as he gave them food too, the dogs didn't care - they "eventually responded to these stimuli as signals for food and failed to show 'even the tiniest and most subtle' signs of pain."

Wow. Think about that for a moment. The dogs learned to uncouple nociceptive input from disagreeable motivational affective input processing. Holy moly. 

The authors continue:

"If these dogs felt pain sensation, then it must have been non-painful pain (Nafe 1931) or the dogs were out to fool Pavlov and simply refused to reveal that they were feeling pain. Both possibilities, of course, are absurd. The inescapable conclusion from these observations is that intense noxious stimulation can be prevented from producing pain, or may be modified to provide the signal for eating behaviour." (p 156)

Source.
Relationship of nociception to pain is that of a fish to a bicycle.
Just imaginary (albeit pretty, carefully sustained) wishful thinking.

Seems so obvious, the way they describe it. They get even more blunt about this:

"The concept of four rigid modalities of cutaneous experience is wrong." (p. 156)

Hard to see how they could be any more blunt.

But they aren't done yet - not by a long shot.


Is there any clinical evidence?

They move over to a heading labelled "Clinical Evidence." Apparently there is none to find. Instead, just a wasteland of failure: here they raise the topic of how phantom limb pain, causalgia (yes, they were still calling it causalgia in 1996), and a category they refer to as 'the neuralgias', "provide a dramatic refutation of the concept of a fixed, direct-line nervous system." They note how surgical ablation of parts of the peripheral or central nervous system didn't succeed in abolishing these kinds of pain permanently. They point out that even gentle touch, vibration, non-noxious stimuli in general, can elicit excruciating pain in some people; furthermore, pain can occur spontaneously for hours with no stimulus whatsoever. New pains can arise in new areas of the body, spread unpredictably into areas where there is no pathology.

SOURCE
Some of the downright painful positions people can sense their phantom limbs to be stuck in

For these reasons, entertaining the idea of a "rigid, straight-through specific pain system" makes no sense whatsoever. None. Nada. Zip.

But they aren't done yet. Oh no. Not done. 


Surely there must be physiological evidence...

SOURCE
"Oh.. NO!!!!"

Sorry, labelled line people. The answer is... no.

• no evidence exists to show that stimulation of one type of receptor fibre, or spinal pathway elicits sensation in only a single psychological modality
• specialized fibres exist, and respond only to intense stimulation - but that doesn't mean they are 'pain fibres' - "that they must always produce pain and only pain when they are stimulated."
• neurography studies show there is no simple relationship between fibre types and quality of sensation
• furthermore, central cells that respond to noxious stimuli are not 'pain cells' - 

"There is no evidence to suggest that they are more important for pain perception and response than all the remaining somaesthetic cells that signal characteristic firing patterns asbout multiple properties of the stimulus, including noxious intensity. The view that only the cells that respond exclusively to noxious stimuli subserve pain and that the outputs of all other cells are no more than background noise is purely a psychological assumption and has no physiological basis. Physiological specialization is a fact that can be retained without acceptance of the psychological assumption that pain is determined entirely by impulses in a straight-through transmission system from the skin to a pain centre in the brain." (p 157)

....................

Next in the history of pain, now that we've covered all the dearth of evidence for a labelled line model for pain, Melzack and Wall discuss all the pattern theories that arose.

Melzack and Katz: Part 6c: History of pain - Ref 4, continued

The paper, Pain.

Part 1 First two sentences

Part 2 Pain is personal

Part 3a Pain is more than sensation: Backdrop

Part 3b Pain is not receptor stimulation

Part 3c: Pain depends on everything ever experienced by an individual

Part 4: Pain is a multidimensional experience across time

Part 5: Pain and purpose

Part 6a: Descartes and his era

Part 6b: History of pain - what’s in “Ref 4”?

Where we left off : Melzack winding up to hit Von Frey's specificity theory of pain out of the park. I'm going to provide the entire build-up here, quote the entire section, so you can get a feel for how charged up the guy is about the topic.

P. 155: 

"Like all psychological theories, von Frey's theory has an implicit conceptual nervous system; and the model is that of a fixed, direct-line communication system from the skin to the brain - of distinct nerves and pathways of four different qualities (analogous to the differently coloured wires of an electrical circuit) running from four kinds of stimulus transducers in the skin to four specific receivers in the brain."

Pain pathway diagrams look a lot like this

Exactly.

The nervous system was studied from the skin in. Pain was studied by poking sore spots on peoples' skin. No one ever knew exactly what went on in the brains of the people who said "Ouch!" It was assumed that there was some "pain center."

But, back to Melzack:

"It is essentially similar to Descartes' concept of pain proposed three hundred years earlier. It depicts a fixed, straight-through conceptual nervous system. It is precisely this facet of the specificity concept, which imputes a direct, invariant relationship between a psychological sensory dimension and a physical stimulus dimension, that has led to attempts at repudiation of the doctrine of specificity in its entirety."

"Consider the proposition that the skin contains 'pain receptors'. To say that a receptor responds only to intense, noxious stimulation of the skin is a physiological statement of fact; it says that the receptor is specialized to respond to a particular kind of stimulus. To call a receptor a 'pain receptor', however, is a psychological assumption: it implies a direct connection from the receptor to a brain center where pain is felt, so that stimulation of the receptor must always elicit pain and only the sensation of pain. It further implies that the abstraction or selection of information concerning the stimulus occurs entirely at the receptor level and that this information is transmitted faithfully to the brain. The crux of the revolt against specificity, then, is against psychological specificity. This distinction between physiological specialization and psychological assumption also applies to peripheral fibres and central projection systems."

I have bolded the bits that stand out for me, the bits I can imagine Melzack being most passionate about.

" The facts of physiological specialization provide the power of specificity theory. Its psychological assumption is its weakness. This assumption will now be examined in the light of the psychological, clinical, and physiological evidence concerning pain (Melzack and Wall, 1962, 1965)."

......

More to come about that.

Labelled line pain science is still all about poking people (or rats, I guess..) until they say/squeak/behave, "Ouch." It's only quite recently in history that behaviour can be seen inside the brain at the same time as the "Ouch!" is uttered. Some have labelled this [erroneously] the "pain matrix." Worse yet, trundling along erroneous labelled line conceptualizations, people got Melzack's neuromatrix confused with the "pain matrix" that they concocted:

SOURCE: "Fig 1  

The pain matrix mainly consists of the thalamus (Th), the amygdala (Amyg), the insula cortex (Insula), the supplementary motor area (SMA), the posterior parietal cortex (PPC), the prefrontal cortex (PFC), the cingulate cortex (ACC), the periaqueductal grey (PAG), the basal ganglia and cerebellar cortex (not shown) and the primary (S1) and secondary (S2, not shown) sensory cortex. For review see Refs. [19, 20]"

[Note the authoritative tone of the declarative statement beneath this image from SpringerImages. They sound like they know what they're talking about, that the hypothetical "pain matrix" is a given. Like it's a noun.]

The big problem with that, is, the same areas that light up inside the brain with an "Ouch!", concurrent with having one's skin poked, light up with any kind of novel stimulus, through any sensory input, including visual, especially if it seems threatening. 

There is still no such thing, therefore, as a "pain" center, or network, or "matrix" in the brain. There is only the neuromatrix itself, generating pain, when and if it has reason to, from its own perspective.

............

To be continued.

REFERENCES

1. Legrain V, Iannetti GD, Plaghki L, Mouraux A. The pain matrix reloaded: a salience detection system for the body. Prog Neurobiol. 2011 Jan;93(1):111-24

2. The Neuromatrix of pain: The Brain from Top to Bottom

3. G. D. Iannetti, A. Mouraux; From the neuromatrix to the pain matrix (and back). Experimental Brain Research August 2010, Volume 205, Issue 1, pp 1-12

Melzack and Katz, Pain. Part 6b: History of pain - what is in "Ref.4"?

The paper, Pain.

Part 1 First two sentences

Part 2 Pain is personal

Part 3a Pain is more than sensation: Backdrop

Part 3b Pain is not receptor stimulation

Part 3c: Pain depends on everything ever experienced by an individual

Part 4: Pain is a multidimensional experience across time

Part 5: Pain and purpose

Part 6a: Descartes and his era

Because this series is a long meander, I want to meander through that first paragraph of "A brief history of pain" a whole lot longer.

"The theory of pain we inherited in the 20th century was proposed by Descartes three centuries earlier. The impact of Descartes’ specificity theory was enormous. It influenced experiments on the anatomy and physiology of pain up to the first half of the 20th century (reviewed in Ref 4). This body of research is marked by a search for specific pain fibers and pathways and a pain center in the brain. The result was a concept of pain as a specific, direct-line sensory projection system."

My old, beloved, well-worn copy

I have the book, Challenge of Pain, which is Ref. 4, mentioned above. I've read it cover to cover. It's full of little post-it 

notes and underlining. 

Part Three, Theories of Pain, starts on page 147.

On the title page appears this quote by Donald Hebb, from 1973:

"The "real world" is a construct, and some of the peculiarities of scientific thought become more intelligible when this fact is recognized... Einstein himself in 1926 told Heisenberg it was nonsense to found a theory on observable facts alone: "In reality the very opposite happens. It is theory which decides what we can observe." "

Melzack and Wall say,

"A theory is primarily an attempted solution to a puzzle or problem - like a guess made by a detective presented with an array of clues in a mystery."

Several theories about pain are then examined. They begin with specificity theory, lay it out for all to ponder:

Specificity theory

• traditional
• often taught as fact rather than theory
• presented as if major answers to pain problems had already been discovered, and all that remained were minor therapy questions
• very powerful theory nonetheless - has given rise to a lot of excellent research and some effective forms of treatment
• has several basic flaws however:
• proposes a specific pain system that carries messages from skin receptors to a pain center in the brain (Descartes)
• contains major assumptions

How it evolved in the last three centuries


1. Müller's doctrine of specific nerve energies (1842): 

• he made formal statement that the brain receives information about external objects only by way of the sensory nerves.
• he implied that activity in nerves represented coded or symbolic data concerning the stimulus object
• he recognized only the 5 classic senses: seeing, hearing, taste , smell, touch
• line of research was for a terminal area in the brain for each sense
• visual and auditory centers were found first: an assumption was made that these were the seat of seeing, hearing: physiologists of the day were convinced this was truth
• Max von Frey proposed a theory of cutaneous senses

2. Von Frey's theory (1894)

Von Frey put together three kinds of information: 

• Müller's doctrine, which he expanded to include 4 kinds of cutaneous modality - touch, warmth, cold, and pain, each with it's own dedicated line to the brain center responsible for the appropriate sensation
• spot-like distribution of heat or cold sensitivity on skin - from that he assumed skin would comprise a mosaic of touch, cold, warmth, and pain
• previous discovery of skin receptors (he was mostly interested in free nerve endings but had opinions on the rest)

He created an interesting example of scientific deduction:

• since free nerve endings are the most common sort, and
• pain spots are found everywhere,
• therefore free nerve endings are pain fibres..
• furthermore, Meissner corpuscles were touch receptors, Krause end-bulbs were cold receptors, and Ruffinis were warmth receptors

3. Others furthered his work

Many experiments, reviewed by Bishop 1946, Rose and Mountcastle 1959, Sinclair 1982, provided evidence for the idea that some one-to-one relationship exists between receptor type, fibre size, and quality of experience.

• very literal interpretation of Müller's doctrine of specific nerve energies
• specificity theorists talk about A-delta-pain, C-fibre-pain, touch fibres and cold fibres as though each had a straight through transmission path to a specific brain centre
• spinothalamic tract was deemed to be the "pain" pathway
• thalamus is deemed to contain a "pain" centrer: it is assumed the cortex can exert inhibitory control

Melzack and Wall point out Von Frey's three main theoretical assumptions

1. Receptor specialization

• the idea "that receptors are specialized, is physiological in nature and has achieved the proportions of a genuine biological law." (p. 154)
• Sherrington (1900, 1906) refined this in terms of "adequate stimulus"- this interpretation is acceptable to those interested in the eventual psychological experience. 

2. Anatomical assumption

• the most obviously incorrect and least relevant aspect of Von Frey's theory
• no one can find any support for this assumption 

"Von Frey assumed that a single morphologically specific receptor lay beneath each sensory spot on the skin and he assigned a definite receptor type to each of the four modalities. The crucial experiment of making a histological examination of the skin under carefully mapped temperature spots has been performed at least a dozen times (see Melzack and Wall 1962) without a single investigator finding any support for Von Frey's anatomical correlations." (p. 155) 

3. Psychological assumption

• the idea that there is any one-to-one correspondence between a single stimulus dimension or given type of skin receptor, and a psychological dimension of somaesthetic experience, is the most questionable Von Frey assumption
• is essentially similar to Descartes concept of pain from 1600's
• depicts a fixed, straight-through conceptual nervous system

"It is precisely this facet of the specificity concept, which imputes a direct, invariant relationship between a psychological sensory dimension and a physical stimulus dimension, that has led to attempts at repudiation of the doctrine of specificity in its entirety." p 155

.............

Next post: the obvious flaws in specificity theory, from the vantage point of psychology, holes so big in it you could drive a truck through them. 

Well, maybe not quite this big,  but big enough, certainly, to cause concern