Tuesday, June 25, 2013

Melzack&Katz, Pain. Part 10c: Conclusion 2: Your brain, not your body, tells you what you're feeling.

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 7bGate 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 9cNeuromatrix: 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
[Previously: From the 2013 Melzack and Katz paper:
"Second, all the qualities of experience we normally feel from the body, including pain, are also felt in the absence of inputs from the body; from this we may conclude that the origins of the patterns of experience lie in neural networks in the brain; stimuli may trigger the patterns but do not produce them."]

[Remember (both of you, or maybe three..), we are now meandering around on a deeper level with a different Melzack paper, a foundational one from 1989, Phantom limbs, the self, and the brain (The D.O. Hebb memorial lecture). It is in this paper his four foundational conclusion are outlined in detail, the four conclusions upon which he based his neuromatrix model. The next section is called The Qualities of Phantom Limb Experience. It's a short section, so here is the whole thing:]

The Qualities of Phantom Limb Experience
"Descriptions given by the amputees and paraplegics indicate the range of the qualities of experience of phantom body parts (Riddoch 1941). Touch, pressure, warmth, cold, and many kinds of pain are common. There are also feelings of wetness, sweatiness, roughness (as when artificial foot steps on pebbles). There is itchiness of the foot - which can be extremely distressing and evoke an intense desire to scratch (actual scratching movements can sometimes relieve the itch) - as well as tickle, tingling, pins-and-needles, formication (like ants crawling on the skin of the phantom limb). Male quadriplegics report feeling erections and women describe sexual sensations in the perineal area. Both describe feelings of pleasure, including orgasms. In addition they often report sensations that characteristically come from the rectum and bladder. Paraplegics may complain of painful fatigue and beg the nurse to stop their legs from making continuos cycling movements even though their legs are lying immobile on the bed (Conomy 1973).  
AN ASIDE: I like how Melzack tends to use first person direct reportage. I suspect this has irritated a lot of people who also research pain attempting to do so from a strictly left hemisphere 3rd-person point of view.. Recall McGilchrist re: why this isn't always such a great idea.
Back to Melzack:
"There is increasing evidence that the sense of effort originates in the brain command and the evidence obtained  with amputees and paraplegics makes it clear that the experiences of effort and fatigue are not solely the result of inputs from the body but from the outputs of a brain process that can be modulated by bodily inputs. Powerful supporting evidence is provided by the observation that the brain "knows" (shows a characteristic electroencephalographic pattern) that the incorrect command to perform a particular response in a test situation has been given even before the response is made (Gevins et al 1987). In other words, feedback is not necessary; all of the relevant activity goes on in the brain.
Exercise physiologists agree. See Fatigue is a brain-derived emotion that regulates the exercise behaviour to ensure the protection of whole body homeostasis, by Timothy David Noakes.  

"The incredible range of qualities of experience felt by patients after amputation or denervation of parts of the body indicates that the origin  of the qualities of experience is not from peripheral inputs but from central processes that are built into the brain. They produce characteristic patterns that underlie the qualities of experience. Sensory inputs may trigger or modulate the patterns but are not essential for their production.

"Conclusion 2: Neural networks in the brain generate all the qualities of experience that are felt to originate in the body: inputs from the body may trigger or modulate the output of the networks but are not essential for any of the qualities of experience."

It blows me away to think Melzack had all this stuff already almost figured out 40 years ago long before there was easy access to information via computer. It didn't used to be easy to be a scholar, or a researcher, not without a lot more hard work, walking back and forth to the library, not without a lot more shelves full of a lot more books, and a lot more file cabinets filled with a lot more scholarly papers to be pored over.

About the topic of neural networks in the brain generating all the qualities of experience felt to originate in the body.. here is Daniel Wolpert on what he thinks the brain is for, a twenty-minute TED talk video, The Real Reason for Brains. So, if Wolpert is right, and the brain is there to make the body move, then it makes perfect sense that there be an intrinsic motivational set-up in there. Move to scratch, move to relieve pressure, move to brush off parasites, even if the body isn't there, in the case of amputated limbs, or else can't move anymore, in the case of quadriplegic limbs. This would be coming from deep inside the 500-million-year-old critter brain, I expect. 

As for the neural network, maybe it doesn't have to be neuronal, maybe it's glial. Check out "A Secret Society of Cells Runs Your Brain". Glia pretty much build the brain in the first place, guide neurons to wherever they need to go as the brain develops. Lest we forget, glia are made from the same cells as peripheral neurons - i.e. neural crest. If any group of embryological cells or part of ectoderm were ever to be chosen for a "Leader and Innovator of Biological Physicality in Mammals" prize, I think I would nominate neural crest cells. 

Further reading:
Michael A Thacker, G Lorimer Moseley; First-person neuroscience and the understanding of painMJA 196 (6) · 2 April 2012

Heather McKenzie, John Quintner, Gillian Bendelow; At the Edge of Being: The Aporia of Pain. 2012 Inter-Disciplinary Press; First edition (November 9, 2012) (Review on Amazon)

Pamela Lyon, Milton Cohen, MD, John Quintner, MB; An Evolutionary Stress-Response Hypothesis for Chronic Widespread Pain (Fibromyalgia Syndrome)Pain Medicine 2011; 12: 1167–1178

Further viewing:
Damasio, Antonio: The quest to understand consciousness. Twenty-minute TED talk video.

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