Melzack&Katz, Pain. Part 11: Now what? We need a new conceptual brain model!

The paper, Pain

Most recent blogposts: 

(NOTE: please find all the rest of the blogposts linked in at the end, from now on)

Part 10: "We don't need a body to feel a body." Part 10b: Conclusion1: The brain generates its own experience of being in a body Part 10c:Conclusion 2: Your brain, not your body, tells you what you're feeling Part 10d: Conclusion 3: The brain's sense of "Self" can INclude missing parts, or EXclude actual parts, of the biological body Part 10e: The neural network that both comprises and moves "Self" is (only) modified by sensory experience

Sorry readers [all three of you..], but I had to make a navigation decision in the course of writing this series. Having all the links to all the other posts in the series at the top was taking up too much room, so from now on you'll find them at the end, just after any references I might want to include. 

Anyway, I planned that we would surface today once the 4 conclusions were drawn, and go back to

Source
Ah, daylight at the end of the tunnel

the 2013 Melzack and Katz paper. I want to stick to that plan, although the Hebb lecture paper remains wonderfully delicious; therefore, I will delve back into it for backup material all the rest of the trip. 

I think we can continue the trip above ground from now on, bearing in mind that our river of discovery is still subject to whatever might happen to it based on the topography of life itself.. 

So, picking up from where we left off, in the last post based on the M&K paper:
"We don't need a body to feel a body."

.... We are now all the way to... Outline of the theory (I wish it had its own link in the paper. But it's a subheading under "Beyond the Gate"). Melzack and Katz deliciously and luxuriously describe each of the aspects of the neuromatrix model, in some detail, with updated references, but not quite as deliciously as does Melzack in the Hebb lecture. This will take a long while to float through. There may even be rapids ahead. I have no idea, really. 

Here we go:

Outline of the theory

"The anatomical substrate of the body-self is a large, widespread network of neurons that consists of loops between the thalamus and cortex as well as between the cortex and limbic system.18,19,21 "

• 
  

• 18. Melzack R. Phantom limbs and the concept of neuromatrix. Trend Neurosci 1990, 13:88–92.
• 19 Melzack R. Phantom limbs, the self, and the brain (The D.O. Hebb memorial lecture). Canad Psychol 1989, 30:1–16.21. Melzack R. Pain and the neuromatrix in the brain. J Dental Ed 2001, 65:1378–1382.
  
  

The 1990 paper is the one with all the interesting drawings in it, one of which I inserted in blogpost 9b. 

"The entire network, whose spatial distribution and synaptic links are initially determined genetically and are later sculpted by sensory inputs, is a neuromatrix." 

M&K are talking about the entire brain. Really. Minus the spinal cord maybe. Certainly from the brainstem forward. 

"The loops diverge to permit parallel processing in different components of the neuromatrix and converge repeatedly to permit interactions between the output products of processing."

SOURCE
Loops converging

This is a bit hard to visualize - I can kind of see the verb of it, but an animation would be nice. In

SOURCE
Loops diverging 

my mind I see intersecting, moving, nested spheres. But it's really hard to depict something like that without access to or expertise in CGI. 

Imagine the jet clouds as spontaneously occurring brain activity, as spoken about by Buzsaki in his book, Rhythms of the Brain. 

Back to M&K:

"The repeated cyclical processing and synthesis of nerve impulses through the neuromatrix imparts a characteristic pattern: the neurosignature." 

Remember, "signature" is something unique. Unduplicable. Well, except by a clever forger. But given every brain is unique like a fingerprint, each neurosignature will also be unique to each individual. Especially since it derives not only from what's unique to each brain's intrinsic moving patterns, but also each brain's experience in its own lifespan. 
Remember what the Aussies did - they called these things neurotags (which I suspect comes from graffiti-writing culture.. and I think my own brain's "style" is likely close to this one, Flava Wildstyle Grafitti Style.)

M&K:

"The neurosignature of the neuromatrix is imparted on all nerve impulse patterns that flow through it; the neurosignature is produced by the patterns of synaptic connections in the entire neuromatrix."

Everything that goes through a particular brain is accepted after it receives some sort of stamp of approval by the neurosignature, "tagged" by the intrinsic neurotag. Then it can add to/become part of the overall neuromatrix. Buzsaki: "..brains are foretelling devices and their predictive powers emerge from the various rhythms they perpetually generate. At the same time, brain activity can be tuned to become an ideal observer of the environment, due to an organized system of rhythms." - first sentence of "Prelude" in his book.

M&K: 

"All inputs from the body undergo cyclical processing and synthesis so that characteristic patterns are impressed on them in the neuromatrix."

SOURCE
Neuromatrix = reverse rock tumbler?

Kind of reminds me of a rock tumbler, only in reverse: instead of smoothing off bits, the neuromatrix adds bits.

M&K:

"Portions of the neuromatrix are specialized to process information related to major sensory events (such as injury, temperature change and stimulation of erogenous tissue) and may be labeled as neuromodules which impress sub signatures on the larger neurosignature."

These sensory experiences aren't continual (tonic) experiences of the body-self - they are cyclic/phasic. They are definitely attention grabbers... evolution must have got rid of any creature that experienced these particular sensory states as a tonic experience.. such creatures would have been so distracted by their own inner sensory experiences that they would have ended up as somebody else's lunch. 

The inclusion of "injury" in the list suggests perhaps "pain" might be going to be discussed at some point. 

The careful reader might have noticed that Melzack's fascination wasn't with pain specifically, it was more with trying to make sense out of sensory experience, e.g., phantom limb sensation etc. It was almost like pain was incidental.. he really was trying to build a new model not of pain, but of something that made sense and could include pain in a better, more logical way. 

M&K:

"The neurosignature, which is a continuous output from the body-self neuromatrix, is projected to areas in the brain—the sentient neural hub—in which the stream of nerve impulses (the neurosignature modulated by ongoing inputs) is converted into a continually changing stream of awareness."

When I think of the word "hub" I think of something inside, or central. I wonder if this sentence

Brainstem, screenshot from
Damasio's presentation

lines up with what Damasio is talking about when he talks about consciousness originating at the brainstem level. I think it might. Line up I mean. Here is Damasio's TEDtalk, The quest to understand consciousness.

In his presentation Damasio highlights the role of the brainstem in consciousness. If the red (upper) part is damaged by, for example, stroke, the patient will lose their "mind" - will develop coma or vegetative state. There may be "feelings" generated (which would move rostrally I suppose), but no "I"-illusion will be available to "feel" them.

If the green (lower) brainstem is damaged the result is locked-in syndrome, a mind that functions perfectly but has no access anymore to a body. The body is completely paralyzed, except maybe for eye-blink in some. (Can you imagine? Imprisoned by a body? Fully awake but in a body that won't move? Ack. Don't use high velocity manipulations on necks. Just don't.)

I don't know if this is what Melzack was talking about, for certain, but it sure looks like brainstem function is at the heart of the interface of brain "self" and body "self" - therefore, provisionally, I'll put this in the spot marked "body-self neuromatrix." 

M&K:

"Furthermore, the neurosignature patterns may also activate a second neuromatrix to produce movement, the action-neuromatrix."

Ha! Shades of Wolpert's The Real Reason for Brains.

"That is, the signature patterns bifurcate so that a pattern proceeds to the sentient neural hub (where the pattern is transformed into the experience of movement) and a similar pattern proceeds through a neuromatrix that eventually activates spinal cord neurons to produce muscle patterns for complex actions."

AN ASIDE: Check out this feature article, The electrified brain: the power and promise of neural implants. 

"It always starts with pain," she says — a hot, radiating pain growing from the base of her skull. Serdans suffers from a neurological disorder called dystonia that, when untreated, leaves her with debilitating muscle pain and movement problems. She keeps it in check with a deep brain stimulation (DBS) device. This pacemaker for the brain works by sending a steady electrical pulse into her globus pallidus. When it's functioning properly, this pulse lets her walk without tripping and move through the world without pain. 

As Spock would say, "Fascinating." 

.....

OK, here's how I see this. The critter brain, aka internal regulation system, does whatever it needs to do. Whatever it's programmed to do. The info flows forward to cognitive-evaluative regions, and motor cortex, and backward to the spinal cord, so all the outflow mechanisms can prepare for the human brain to do whatever it needs to do, in seamless concert with the body, in this case, the puppet. 

Neuromatrix? 

The critter brain has to organize everything in advance so that it can manage the all important homeostatic functions, like blood pressure etc. The critter brain is like a combination of Scotty ("I canna giv'er ana'more Captain - she's gonna blow!") in engineering (hindbrain) and Captain Kirk with all his passionate drive and emotional outbursts (limbic system).

I think the rostral centers are Spock. He is mostly just thoughtful and reflective. His biggest outburst is "Interesting." or a bit more charged.. "Fascinating." His job is to inhibit, not inflame further. But also to act, appropriately. 

We have reached the end of that short section titled "Outline of the Theory" - I don't want to leave the topic entirely until I go back to the Hebb paper and fill in more detail for myself, though. So the next few blogposts will still be about the outline. We won't get to the details of each of the neuromatrix domains for a few more days, at this rate. 

Further reading

György Buzsáki, Rhythms of the Brain. Oxford University Press 2006 (full pdf)

Google Scholar: Ronald Melzack publication list/citation count
The electrified brain: the power and promise of neural implants

........

Previous blogposts

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 Part 6e: Pattern theories in the history of pain Part 6f: Evaluation of pain theories Part 6g: History of Pain, the cautionary tale. Part 6h: Gate Control Theory.

Part 7: Gate control theory has stood the test of time: Patrick David Wall;  Part 7b: Gate control: "The theory was a leap of faith but it was right!"

Part 8: Beyond the gate: Self as mayor Part 8b: 3-ring circus of self Part 8c: Getting objective about subjectivity

Part 9: Phantom pain - in the brain! Part 9b: Dawn of the Neuromatrix model Part 9c: Neuromatrix: MORE than just spinal projection areas in thalamus and cortex Part 9d: More about phantom body pain in paraplegics

Melzack&Katz, Pain. Part 10e: Conclusion 4: The neural network that both comprises and moves "Self" is (only!) modified by sensory experience

The paper, Pain

Previous blogposts:

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 Part 6e: Pattern theories in the history of pain Part 6f: Evaluation of pain theories Part 6g: History of Pain, the cautionary tale. Part 6h: Gate Control Theory.

Part 7: Gate control theory has stood the test of time: Patrick David Wall;  Part 7b: Gate control: "The theory was a leap of faith but it was right!"

Part 8: Beyond the gate: Self as mayor Part 8b: 3-ring circus of self Part 8c: Getting objective about subjectivity

Part 9: Phantom pain - in the brain! Part 9b: Dawn of the Neuromatrix model Part 9c: Neuromatrix: MORE than just spinal projection areas in thalamus and cortex Part 9d: More about phantom body pain in paraplegics

Part 10: "We don't need a body to feel a body." Part 10b: Conclusion1: The brain generates its own experience of being in a body Part 10c:Conclusion 2: Your brain, not your body, tells you what you're feeling Part 10d: Conclusion 3: The brain's sense of "Self" can INclude missing parts, or EXclude actual parts, of the biological body

[Previously: From the 2013 Melzack and Katz paper:

Fourth, the brain processes that underlie the body-self are ‘built-in’ by genetic specification, although this built-in substrate must, of course, be modified by experience, including social learning and cultural influences. These conclusions provide the basis of the conceptual model18,19,21 depicted in Figure 3. ]

18. Melzack R. Phantom limbs and the concept of neuromatrix. Trend Neurosci 1990, 13:88–92.
19. Melzack R. Phantom limbs, the self, and the brain (The D.O. Hebb memorial lecture). Canad Psychol 1989, 30:1–16.
21. Melzack R. Pain and the neuromatrix in the brain. J Dental Ed 2001, 65:1378–1382.

Figure 3: 

SOURCE

Well, well, we are nearly there, if by "there" you agree it means, "end of our little detour underground." 

We are going to check out the rationale for Melzack's fourth and final conclusion. Back to the Hebb lecture for just a little bit longer. 

Melzack:

The Innateness of Phantom Limb Experience 

"There is convincing evidence that a substantial number of children who are born without all or part of a limb feel a vivid phantom of the missing part." [Weinstein et al 1964, 1969; Poeck 1964, 1969] "..have made a powerful case that phantoms are experienced by children who are born without a limb (congenital aplasia) or who have lost it before the age of 5."

This section is quite long. Apparently there had been entrenched belief (who knows where these weird ideas come from?) that children who were born without a limb or lost a limb before age 5 wouldn't experience phantoms. Melzack painstakingly gathered evidence to the contrary, all the way back to Valentin 1836. 
An interesting point Melzack notes: estimated percentage of phantoms in congenital aplasia, 18%. In adult amputees, virtually 100%. If the child has worn a prosthesis before age 7, they are more likely (81.2%) to retain a phantom than if they wore one after age 7 (52.6%). 

("Eyew" factor coming up..)
To back up his point, that phantoms are intrinsic to the brain, Melzack discusses some research done on monkeys: Infant monkey upper limbs were "deafferentated" (sounds awful.., but if you think that was awful...), their eyelids were sewn shut so they couldn't learn movement through visual stimuli. 

By age 3 months, the monkeys were using their arms to support walking, and could grasp. Smart little monkeys; smart little monkey brains built to move. Recall Daniel Wolpert. 

"The only reasonable explanation of such spatially coordinated behaviour in the absence of vision and sensory feedback from limbs after birth is that the monkeys possess built-in brain mechanisms for a phantom body capable of meaningful actions in three-dimensional space."

Capable of meaningful actions in three-dimensional space. That's what brains are for. Manoeuvring huge colonies of cells (in us, one-tenth human, nine-tenths other) through space, as a singular organism, (hopefully) protecting it from harm (unless it has been "deafferentated"..), much of its sense of a "body" already pre-programmed and pre-deployed.

He adds, that, of course, sensory inputs are relevant - people can "feel" the corn or bunion on their phantom toes, etc. 

"Heredity and environment clearly act together to produce the phenomena of phantom limbs."

Conclusion 4: The neural network that underlies the experience of the body-self is genetically determined but can be modified by sensory experience.


There we are, then. All four conclusions, all wrapped. We will conclude the 1989 paper in the next blogpost (I hope) and get back out from underground, into present time, and back into the 2013 paper where we left off. 

Melzack&Katz, Pain. Part 10d: Conclusion 3: The brain's sense of "Self" can INclude missing parts, or EXclude actual parts, of the biological body

The paper, Pain

Previous blogposts:

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 Part 6e: Pattern theories in the history of pain Part 6f: Evaluation of pain theories Part 6g: History of Pain, the cautionary tale. Part 6h: Gate Control Theory.

Part 7: Gate control theory has stood the test of time: Patrick David Wall;  Part 7b: Gate control: "The theory was a leap of faith but it was right!"

Part 8: Beyond the gate: Self as mayor Part 8b: 3-ring circus of self Part 8c: Getting objective about subjectivity

Part 9: Phantom pain - in the brain! Part 9b: Dawn of the Neuromatrix model Part 9c: Neuromatrix: MORE than just spinal projection areas in thalamus and cortex Part 9d: More about phantom body pain in paraplegics

Part 10: "We don't need a body to feel a body." Part 10b: Conclusion1: The brain generates its own experience of being in a body Part 10c: Conclusion 2: Your brain, not your body, tells you what you're feeling

[Previously: From the 2013 Melzack and Katz paper:

Third, the body is perceived as a unity and is identified as the ‘self’, distinct from other people and the surrounding world. The experience of a unity of such diverse feelings, including the self as the point of orientation in the surrounding environment, is produced by central neural processes and cannot derive from the peripheral nervous system or spinal cord. ]

[Remember, we're still underground, trying to follow that river that sank down down down into another paper a few blogposts ago, Melzack R. Phantom limbs, the self, and the brain (The D.O. Hebb memorial lecture), the one that explains the Four Conclusions in more detail. 

That word "Self" appears. Uh-oh. That's a tough one. No one has ever been able to define "Self" to anyone else's satisfaction, same as no one has ever been able to define "consciousness" or "pain" to anyone's satisfaction.] 

SOURCE
How are we going to get around this? 

Let's find out what Melzack had to say. The next section (page 5) is titled, "The Unity of the Phantom Limb Experience."

Unity.  Oneness. Seamlessness. Indivisibility. 

"One of the most striking features of the phantom limb or any other body part (including the body in many quadriplegics) is that it is perceived as an integral part of the body. Even when a foot is dangling "in mid-air" (without a connecting leg) a few inches below the stump, it is still felt to be part of the body and moves appropriately with the other limbs and torso. When a prosthesis is put on, the dangling phantom foot usually lowers into the show and the whole artificial leg is felt as a part ofd the body. The reality of these experiences derives in large part from the feeling of unity of the phantom part and the real body." 

My bold. 

"An integral part of the feeling of unity of the phantom limb (or other body part) with the remainder of the body is the feeling that the phantom is part of one's self." 

My bold again. 

"The phantom foot, penis or breast is described not only as real but as unquestionably belonging to the person. While this may seems self-evident, there is reason to believe that particular brain processes underlie the experience of the self. Just as extraordinary as the persistent experience of a limb after it has been amputated is the converse - the denial that a part of the body belongs to one's self (Denny-Brown et al 1952, Mesulam 1981)"

The Mesulam abstract mentions a hypothetical four-part network comprised of parietal, frontal, limbic and reticular regions as important for a unified sense of extrapersonal space, based on lesion studies; damage to any of these areas results in region-specific neglect impairment. 

Back to Melzack:

"Typically, the person, after a lesion of the right parietal lobe or any of several other brain areas (such as the left parietal lobe, cingulum, thalamus and midbrain) denies that a side of the body is part of himself and even ignores the space on that side. There are several descriptions of patients who topple out of their hospital bed because they believe that a strange leg is in their bed, which they then try to throw out of bed with the consequence, of course, that the rest of the body follows the leg. Generally the leg (or arm, or whole side of body) is treated negatively - as undesirable."

Think of how distressing it would be, to be attached to something, physically, that you really did not want as part of your personal existence. Please, if this ever happens to me, just shoot me. But it looks like it can go the other way sometimes, too:

"On one occasion however, a patient thought that the leg belonged to an attractive woman and was happy to have it share his bed."

Melzack continues:

"From these cases and many others like them, it is evident that the brain processes that underlie the signal that says: this is my body, it belongs to me, is part of my self." 

My "Self" - my "I"-illusion, created for me by my brain, without which I would have no sense of seamless continuity (of me inside my physicality) or separation (from the rest of the world). All messed up about the space, inside and out. A network my brain develops that produces personal boundaries in time and space. 

Melzack again:

"We take this for granted. But the effects of these lesions indicate that there are parts of the brain which impart a special signal that provides the basis for experience of self. When these areas are lost, the person denies that a part of the body belongs to the self." 

Or if they never formed from the beginning - let's not forget xenomelia and Brugger. 

Melzack:

"These patients provide powerful evidence that the brain distinguishes between self and not-self. The self is accepted; the not-self is denied. An artist who suffered this kind of brain damage would simply not paint one side of his face in his self-portrait. As he began to improve, he added more details to the previously denied face. However, more than the self is involved. When these people draw the numbers of the hours on a clockface, they crowd all the numbers on one side. Or if they draw a daisy, they draw the petals on one side only. The self, then, includes the space that surrounds the self (Denny-Brown, Meyer & Horenstein 1952; Mesulam 1981)"

"The not-self is not merely denied; it is rejected outright. The hostility and rejection with which the not-self is regarded is indicated by the instances in which the not-self leg is thrown violently out of bed or the patient desperately asks the nurse or doctor to remove the not-self leg or arm from the bed. The negative feelings are evident."

My bolds. Yup, I'd certainly feel that way. 

[I feel that very same way about "pain" - it isn't me, doesn't belong to me, I want to kill it. My brain rejects it as not-self. 

Or maybe that's just me. Maybe that's why I knew what I wanted to do in life at a very young age, why I went and got a license to touch people, hire myself out as a painkiller, a hired hand, out there in the greater world.] 

Melzack again:

"A moment's thought about how each of us would feel if a stranger's leg or arm were placed in our bed and we were told that it belongs to us makes the denial and hostility easy to understand." 

My paraphrase: 

He's saying c'mon, put yourself in someone's shoes here for just a frickin' minute. Take off your blinkers and exercise your theory of mind on this. Use whatever you have in there that pass for mirror neurons combined with some imagination. How the heck would YOU feel? Wouldn't you feel invaded? Angry? Hostile? 

Melzack is so much more smooth:

"If a strange leg were put in my bed, no amount of coaxing would convince me that the leg is actually mine - that is, belongs to my "self."

He tantalizingly mentions motor behaviour, how revealing it is:  

"Extraordinarily, after particular brain lesions, this denial occurs even though the real limb is intact and is even used in movements such as walking, dressing, and eating. If not paralyzed, the limb is used in a natural way to put on clothes, but the arm that is doing the dressing is itself not put through the sleeve of a shirt or other garment; it is ignored as not-self."

He mentions a story told by Denny-Brown about a woman (elderly, religious, fastidious) who dressed in the right side of her body in her usual style, but left the left side exposed "heedlessly." Hmmnn. 

So:

Conclusion 3: The experience of the body has a unitary, integrated quality which includes the quality of "self" - that the body is uniquely one's own and not that of any other individual.  

.....

My take: 

The "I" illusion can INclude whatever bits of biological body it wants, even if they don't exist.

The "I" illusion can EXclude (disown) whatever bits of biological body it wants, even if they do exist. 

.......

AN ASIDE:

I wonder, though, if sense of self varies across different cultures. How "learned" (i.e., externally influenced) might an inherent brain-network sense of self, or "I" illusion, be? 

If in fact it's intrinsic, how much might it be overridden by circumstance of birth? 

As a female looking around at the world I see cultures where women are property of their families, seen as either assets or liabilities to a "group", like livestock, not as individuals in their own right. They are not allowed their own identities. They are known, socio-legally, only as the daughter of so-and-so or the wife of Who-ever. Could they ever be able to "self"-organize and toss off their oppressors? What do their "self" neurotags look like? Do they even have any? 

These female humans exist within entrenched historical, cultural, religious, social and legal invisibility. The culture overrides any brain network they might have intrinsically been born with. They do not have any rights over what happens to their own body, particularly from the waist down - yet they bear complete responsibility for whatever might happen to said body from the waist down, including death by stoning. They are not allowed any personal boundaries, near as I can tell. They must rigidly obey those proscribed by their culture. 

I just cannot fathom it. My brain has neuroplasticized around the freedom to be female, a legal human with an identity, paying taxes, and a self with personal boundaries, all at the same time.

Casting my own Theory-of-Mind, and comparing my own "I" illusion, to what my mirror neurons react to when they contemplate this aspect of vast swathes of humanity culturally imprisoned by mere biological in-y-ness, as opposed to out-i-ness, makes my particular "justice-for-"Self" neurotag's blood boil... The thought of individuals being denied access to develop their own inherent self-networks makes mine pretty cranky. Probably a topic, though, for some whole other blog, not this one. 

Additional thought: I wonder what phantom limb feels like in these individuals? 

Further reading:

Deric Bownds: The "I" Illusion.