Saturday, July 06, 2013

Melzack & Katz, Pain. Part 13: Pain and Neuroplasticity

The paper, Pain

Most recent blogposts:

Part 12: Action! 12b: Examining the motor system, first pass. 12cMotor output and nervous systems - where they EACH came from Part 12d... deeper and deeper into basal ganglia Part 12e: Still awfully deep in basal ganglia Part 12f: Surfacing out of basal ganglia Part 12gThe Action-Neuromatrix


OK! New section! The river with very nice smooth sailing for an entire section.  


We're looking at the Melzack Katz paper, the section Beyond the Gate, and we've arrived to a broad topic, neuroplasticity and pain. This is a very short section (...disappointingly short, even). 

Neuroplasticity and Pain
"There was no place in the specificity concept of the nervous system for ‘plasticity,’ in which neuronal and synaptic functions are capable of being molded or shaped so that they influence subsequent perceptual experiences. Plasticity related to pain represents persistent functional changes, or ‘somatic memories,’29–31 produced in the nervous system by injuries or other pathological events. The recognition that such changes can occur is essential to understanding chronic pain syndromes, such as low back pain and phantom limb pain that often destroy the lives of the people who suffer them."
That's it. That's the entire section!
Here are the references.

29. Salomons T, Osterman JE, Gagliese L, Katz J. Pain flashbacks in posttraumatic stress disorder. Clin J Pain 2004, 20:8387.

30. Katz J, Melzack R. Pain “memories” in phantom limbs: review and clinical observations. Pain 1990, 43:319336.
31. Katz J, Vaccarino AL, Coderre TJ, Melzack R. Injury prior to neurectomy alters the pattern of autotomy in rats. Behavioral evidence of central neural plasticity. Anesthesiology 1991, 75:876883.

I think this section could have been a lot longer. 
I can understand why they left out vast chunks of research into spinal cord neuroplasticity - I suppose they are mostly interested in what goes on above the level of basal ganglia. I don't understand though, how they left out this juicy paper, Central neuroplasticity and pathological pain from 2001, by Melzack, Coderre, Katz, Vaccarino.

It could be that this section is short, because the implication (according to Doidge, at least - see video posted below) is that chronic pain is the "dark underbelly of neuroplasticity."

Meanwhile, it's a big hopeful topic for all those of us who work with people in pain every day, helping them sort through their neurotags, offering their brains something new in the way of sensory input (non-nociceptive works best according to me) with subsequent different motor output (less painful). In "Neuroplasticity and Pain: What does it all mean?" Philip Siddall says [excerpt], 

"...these [neuroplasticity] findings provide reasons for hope. The first reason is that, although it may sound strange, neuroplasticity is by nature plastic. This means that although nervous system changes can occur, they are not necessarily irreversible. Some authors have adopted the view that central processes can become so dominant and fixed that they generate pain in the absence of peripheral input. Fortunately, there is not a great deal of evidence to support this view. Although nervous system injury such as damage to the spinal cord may give rise to structural changes that are extremely resistant to change, activity-dependent neuroplasticity (central changes that are dependent on the level of incoming signals to the spinal cord and brain) in response to nociceptive inputs is not so resistant... It has been shown that people who have pain associated with osteoarthritis of the hip have neuroplastic changes, including a reduction in grey matter volume in some brain regions. Importantly, these changes have been shown to reverse following successful hip surgery and a decrease in pain. This suggests that neuroplasticity is dependent on pain rather than the other way around...There is no room for the old dualist view of pain being either real or psychological. Cognitive and emotional processes strongly engage brain and spinal cord pathways that are directly involved in altering the responsiveness of pain pathways. By doing so, psychological factors influence neuroplastic processes and thus directly modify the pain experience." 

I've been chewing through a paper by David Baldwin, Primitive Mechanisms of Trauma Response: An Evolutionary Perspective on Trauma-Related Disorders, which adds a large amount of texture to the topic, in advance of the section coming up on stress and pain. It was recommended by John Quintner on a BodyInMind blogpost recently, by John Loeser. (Remember him? He wrote that paper with Melzack way back in 1978 about phantom body pain in paraplegics.) 

Meanwhile, here are some more neuroplasticity resources.

More Resources
1. 55 minute video of Norman Doidge, who wrote the book, The Brain That Changes Itself. 

4. A 5-minute video on neuroplasticity for those without any time to luxuriate in Doidge's video. 


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 Part 10c:Conclusion 2: Your brain, not your body, tells you what you're feeling Part 10dConclusion 3: The brain's sense of "Self" can INclude missing parts, or EXclude actual parts, of the biological body Part 10eThe neural network that both comprises and moves "Self" is (only)modified by sensory experience
Part 11We need a new conceptual brain model! Part 11b: Intro to a new conceptual nervous system Part 11c: Older brain models just don't cut it Part 11d: The NEW brain model!

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