Wednesday, May 15, 2013

Melzack & Katz Pain2013 Part 2: Pain is personal

The paper, Pain.

Part 1 of this adventure meandering through it. 

Yesterday we made it through the first two sentences of the abstract. [Which was a classic example of how meandering my mind is. Like a stream on the prairie. It goes anywhere it can, always very slowly, because there isn't much of a gradient in there.]

Anyway, today we continue. Third sentence of the abstract:
"Pain is a personal, subjective experience influenced by cultural learning, the meaning of the situation, attention, and other psychological variables."
The example that comes to mind in just the last couple months, is Kevin Ware. [graphic warning]
So, this guy's leg crumples as he lands on it, something he's done thousands of times, probably, only this time, for some weird reason, his tibia, one of the strongest freakin' bones in the whole body, breaks on landing, and he falls over. Here is a video. [graphic warning]

Several teammates crumple too. It's like they are part of a superorganism. Maybe they are. A symbolic superorganism called a team. Maybe it's just mirror neurons. 

Kevin Ware certainly looks like he had pain at the time - his face contorts for a few seconds. But he is conscious, remains calm, tells his teammates to get back out there and win, doesn't faint or throw up. Later he declares he didn't feel any pain, was just surprised by the episode. 
"I saw the bone six inches out ... 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." 

His face looked more like it expressed pain than fear, though. Just for a few seconds. He likely did experience some nociceptive input, which enters S1into BA3a, according to Smith, from projection neurons associated with the spinothalamic tract [along with proprioceptive input from muscle spindle receptors via ventroposterior superior nucleus..]. A deltas are pretty swift - they are myelinated nociceptive fibres that must end up somewhere,  although the only information I've been able to glean about nociception and S1 has been about C's. My guess is, they probably are processed and their stimulus intensity recorded by the other three areas that process mechanoreception intensity from skin. 

4 Brodmann areas are associated with S1 cortex
BA3a handles proprioceptive, and SOME nociceptive input. The other three areas handle cutaneous mechanoreceptive input. 

S1 doesn't do anything but record intensity of a stimulus. It doesn't entertain any opinion on what the stimulus might mean. It just ... objectively records intensity. [See Smith, and the blogpost on David Seminowicz for more about that, and a list of references.] If the prefrontals are working hard, i.e., if there is a threat situation going on and adrenaline is pumping and the prefrontals are soaked in noradrenalin from locus ceruleus, they'll be able to kick in that whole descending modulation business in a favorable way

But... what did Kevin Ware do with his prefrontals when he experienced a burst of nociception somatotopically represented in the dorsolateral periaqueductal grey? He stayed level - he didn't conclude [..or rather, his brain didn't decide] that he must be dying, then try engage his own possum reflex through the ventrolateral part of periaqueductal grey - he/his brain didn't want to deploy opioids - he was up for a fight because he's just been playing basketball, he was on the floor with an injury, he realized he couldn't get back up so there wasn't much around to fight with anymore except his own nociceptive input, and I bet he decided to fight with that instead. Not a conscious decision, just his brain deciding for him, based on the circumstances and whatever was racing through it, anyway, in terms of neurochemistry. 

So, good for him. 


June 3/13: Update: Video, depicting Ramon Ortiz of the Toronto Blue Jays reacting to an elbow injury sustained while pitching a baseball game, his pain behaviour as he experienced his own injury: Compare the two events. In Ware's case the injury was outrageously visible, and the teammates and crowd did a lot of reacting. In Ortiz' case, it's a closed injury. Psychosocial context and outward behaviour is different.
Who do you think might carry a more entrenched pain neurotag in the future? 


Anonymous said...

Brilliant post, loving this series already!

What an amazing example. Really enjoyed your thinking process in regards to what might be going on upstairs.

Looking forward to Pt 3


Diane Jacobs said...

Thank you for your comment Tim.
At this rate, there will be approximately one blog post for every sentence in the paper. That's going to keep me busy for awhile.

Anonymous said...

Funny. This is posted on my birthday. Thank you.