Saturday, August 31, 2013

The Skin as a Social Organ. Part 2b: Proxemics

The paper, The skin as a social organ

Previous introductory blogpost to this series.
Preamble: Random thoughts on spas

Part 1: Dual nature of touch: as PTs, do we "get" this? Part 1a: Touch can be pleasant, rilling Part 1b: Vallbo on C-tactiles 

Part 2a: Different kinds of touch

Next part of Skin as a Social Organ re: touch in affiliative behaviour and communication: 

"What is the role of ‘‘pleasantness’’—the positive hedonic facet—in these categories of human social touch? First, pleasant touch may serve as a foundation for affiliative behavior. Second, it may provide a mechanism for the formation and maintenance of social bonds. Third, it is a nonverbal means for the communication of emotions. It is important to note that the above varieties of social touch are not always welcome or even pleasant; touch has an intricate relationship with culture, context, and gender (e.g., Dibiase and Gunnoe 2004), and, depending on these factors, pleasure easily tips into aversion and disgust."
Dibiase R, Gunnoe J (2004) Gender and culture differences in touching behavior. J Soc Psychol 144:49–62

Oh yes, yes it can - pleasure from touch can tip easily into aversion and disgust. Easily. Aversion, disgust, and withdrawal from nociception are all processed by the insular cortex and anterior cingulate cortex.

As therapists who can touch people, we enjoy extended social trust from our patients that overrides their aversion, maybe disgust.. i.e., from being touched by a stranger. They also deliberately inhibit the urge to withdraw from nociceptive discomfort. Maybe too easily.

We really should take care to not add any nociception to an already overloaded nervous system if we can possibly help it. All it does is make nervous systems tense up unconsciously in some other part of the motor output system.

If we think of pain output as the patient's critter brain all freaked out about something, and it biting down hard on the patient from the inside, then it's easy to see why: Why hurt a distraught horse? be Monty Roberts instead - speak it's language, non-verbally: Why hurt a frightened snarling dog? Be Caesar Milano instead. Be the alpha dog, but be kind - outstare it instead. 

The paper cited is a nice fat 15 page paper that looks carefully at power differential, status, culture, gender. It looks at touch as a means of communicating dominance in all these things, to others. I didn't see anything in it while reading through it about aversion or disgust, though, just a cataloguing of findings in general from other researchers and more about three cultures more specifically. Nothing one doesn't already know from general reading.. 

"Proxemics" factor in big time. Apparently, people from cold climate cultures prefer relatively larger physical distances when they communicate. People in cultures in warmer climates cozy up more. 

I have noticed this personally visiting Mexico, Central American countries, Brazil. Lots more physical contact. Not at all unpleasant, just different. Unless you happen to be allergic to perfume, as I am. 

A recent tidbit on this: if you have anxiety trait, you need more peripersonal space.  Size of Personal Space Is Affected by AnxietyGiandomenico Iannetti and Chiara Sambo. Better safe than sorry? The safety margin surrounding the body is increased by anxietyThe Journal of Neuroscience, 2013 
The defensive peripersonal space represents a “safety margin” advantageous for survival. Its spatial extension and the possible relationship with personality traits have never been investigated. Here, in a population of 15 healthy human participants, we show that the defensive peripersonal space has a sharp boundary, located between 20 and 40 cm from the face, and that within such space there is a thin, “highest-risk area” closest to the face (i.e., an “ultra-near” defensive space). Single-subject analysis revealed clear interindividual differences in the extension of such peripersonal space. These differences are positively related to individual variability in trait anxiety. These findings point to the potential for measuring a range of defensive behaviors in relation to individual levels of anxiety. Such measures will allow developing procedures to test risk assessment abilities, particularly in professions that require reacting quickly to aversive stimuli near the body, such as firemen, policemen, and military officers. This may also lead to possible interventions to improve their performance under pressure.
I could have told them that... seems like a no-brainer. 

Sunday, August 25, 2013

The Skin as a Social Organ. Part 2a: Different kinds of touch

The paper, The skin as a social organ

Previous introductory blogpost to this series.
Preamble: Random thoughts on spas

Part 1: Dual nature of touch: as PTs, do we "get" this? Part 1a: Touch can be pleasant, rilling Part 1b: Vallbo on C-tactiles

So, time to start tackling the section of the paper titled, Touch in affiliative behavior and communication.
The first paragraph, divided by me into numbered sentences:

"The most salient nonsexual, positively hedonic forms of social touch can be tentatively divided into categories.
"1. ‘‘Simple’’ touch involves brief, intentional contact to a relatively restricted location on the body surface of the receiver during a social interaction; the person who pats the hand of the little old lady on the bus or gently touches the waiter’s elbow while making a request is engaging in ‘‘simple’’ touch.
"2. ‘‘Protracted’’ touch involves longer and often mutual skin-to-skin contact between individuals, and usually includes a component of pressure, for example embracing, holding hands, and cuddling.
"3. Finally, ‘‘dynamic’’ touch involves continuous movement over the skin from one point to another, and can often be repetitious, as in stroking, rubbing, and caressing.
"4. Tickling presents an additional special category, which is associated with playful behavior (especially with children) and is not likely to occur in the context of everyday interactions."

So, I wonder which of their categories grooming for stress and pain reduction would fall into?

The way I do manual therapy is, I think, based on this little category list, a cross between "protracted" and "dynamic." It isn't brief, like "simple touch," and no tickling is involved..

It's "protracted" in that I sit in one place for awhile, until I feel different output in that place, then move on. It's certainly not mutual physical contact however.. I am paid to be the toucher, not the touchee
Not that the patient's brain isn't hard at work feeling me touching its organism's nerves.
Not that it isn't busy incorporating me into its representational maps, as it would a white cane if it were a blind person, feeling the sidewalk through one.
Not that it isn't taking the opportunity to refresh its own maps of its own temporarily less-painful "body."
Just that no one has their hands on my skin.

It's "dynamic" in that once I feel a slowing down or stopping of any further "busy-ology" going on under my hands through my fingers, I move on to a new place. Sometimes I add some finger flutter type of provocation to skin, just to see what the nervous system is going to do in response. I guess this would be the equivalent of fly fishing, where you throw in the lure, then wiggle it a bit, to see if you can entice anything to come over and investigate. But I don't slide around over skin.. I try to distort it, lengthen it while holding onto to it, not slide over it.
I figure I'm engaging Ruffini's when I do that. Sometimes I even use Dycem, as I have small hands, and sometimes skin can be dry, or slippery, or so firmly attached that it's hard to deform it at all.

I think they should have added a 5th category, touch done with the intent to relive nociceptive input. Anti-nociceptive touch.


Saturday, August 24, 2013

The Skin as a Social Organ: Part 1b: Vallbo on C-tactiles

The paper, The skin as a social organ

Previous introductory blogpost to this series.
Preamble: Random thoughts on spas

Part 1: Dual nature of touch: as PTs, do we "get" this? Part 1a: Touch can be pleasant, rilling

The third paragraph in the intro has two sentences, the first of which is:
"Hedonically positive touch in human social interactions is ubiquitous despite cultural differences in its regulation, with roles ranging from the casual to the sexual. Sexual and parent–infant interactions are undeniably vital arenas of social touch. For example, the erotic dimension of human touch affects everyday interactions even among people who are not sexually involved, by introducing a culturally influenced ‘‘erotic barrier’’ which precludes certain types of casual touch (Vallbo et al. 2007; Heslin and Alper 1983)."  
Vallbo Å, Olausson H, Wessberg H (2007) Pleasant touch. In: Squire LR (ed) Encyclopedia of Neuroscience. Academic Press, Amsterdam 
Heslin R, Alper T (1983) Touch: a bonding gesture. In: Wiemann JM, Harrison RP (eds) Nonverbal interaction. Sage, Beverly Hills
I don't have the Heslin book but I do have access to the Vallbo reference, a 7-page chapter in an encyclopedia of over 10,000 pages (yup, it's huge).

Anyway, I pulled it up to see what it had to say. Here are some interesting bits.
"The canonical view of human physiology is that light touch is signaled by large and fast conducting myelinated Ab-afferents alone. However, in the last decades it has been demonstrated that human skin is also innervated by unmyelinated afferents responding to light touch (CT-afferents). They conduct impulses at a speed of about 1 m s ¯¹ whereas Aβ-afferents are about 50 times faster ... Six different kinds of Aβ-afferents with separate physiological properties have been identified in human skin in addition to the CT-afferents (Table 1)."
Table 1 goes to a little chart of skin receptors of hand and forearm, both hairy and glabrous (non-hairy, like on the palm) skin. Here it is.

From Vallbo chapter, p 742

As you can see from the table, hairy skin has these C-tactile fibres and glabrous skin does not. 
People assumed humans didn't have these. Because we're less hairy than most animals, maybe. But, then it was found, quite recently, really, that in fact, we did:
"It should be pointed out that unmyelinated tactile afferents were demonstrated long ago in the hairy skin of various animals but they have not been found in the pad skin which corresponds to the glabrous skin in man – where CT-afferents are lacking as well. In animals the unmyelinated tactile afferents are often denoted as low threshold mechanoreceptive C-afferents (C-LTM). For long it was assumed that this system of afferents had faded away in the process of evolution from rat, rabbit, and cat to man until microneurogaphy demonstrated CT-afferents in man in the beginning of the 1990s."
From the section titled "Functional Properties of CT-Afferents":
"The CT-afferents are equally sensitive to skin deformation as many of the Aβ-afferents. They respond to indentation forces in the range 0.3–2.5 mN as tested with von Frey monofilaments and they produce high-frequency trains of action potentials (50–100 impulses s¯¹) to pleasant touch stimuli. It should be recalled that maximal impulse frequency recorded from afferent C-fibers is about 100 impulses s¯¹. In contrast, Aβ-afferents may fire close to 1000 impulses s¯¹. It is of interest that, in addition to these two groups of sensitive tactile afferents, some of the nociceptive afferents may respond to innocuous touch as well. However, their sensitivity is low and their response to pleasant touch is minimal, usually not more than one or two impulses."

Well: that seems odd, doesn't it? Maybe it has to do with expectations.

"While CT-afferents share the high sensitivity with the Aβ-afferents, the physiological properties of the two groups differ in most other respects. Aβ-afferents fall in two distinct groups with regard to response to steady-state skin deformation (Table 1). The fast adapting units do not respond at all, that is, they lack static sensitivity altogether, while the slowly adapting units provide a continuous discharge for minutes or more. Actually, many Ruffini units may be firing continuously for life."

Wow. That's a long time.
"In contrast, the CT-afferents have intermediate adaptation properties. They respond initially with a burst of high impulse rate, while the rate often falls to zero after a few seconds of sustained indentation. The discharge may then reassume after another few seconds, then wax and wane to finally stop altogether. CT-afferents lack the potential of the Aβ-afferents to code fast events. They respond well to slowly moving stimuli but poorly to brisk movements and vibration. Hence, their dynamic response range is limited to low frequencies. Stimuli which are particularly efficient to evoke a massive CT-input are slowly moving, caress-like stimuli over large skin areas with the hand or a broad artist paintbrush."
A friend of mine treated a woman whose fingers had been traumatically amputated in a car accident, for face pain secondary to dental problems, brushing it with a lovely, fat, sable make-up brush; the woman's phantom finger pain reduced.
My friend deduced that the representation of the face maybe now contained the finger representation due to homuncular smudging. Anyway, brushing worked well.
Eventually the woman could tolerate mirror therapy, and finally, able to wear prosthetic fingers, got back out into the world after months of disability, instead of having to stand at the sink all day and let water run over her stumps to get any relief.

"A prominent feature of the CT-afferents is that they are highly fatigable. When identical stimuli are repeated, the first stimulus usually evokes a much larger response than the following. This feature suggests that the system is particularly interested in novel events. When a local skin deformation is released, CT-afferents may produce an after-discharge that may last for many seconds. However, the duration varies a lot even within the individual unit depending on temperature, previous history, and other nondefined factors. An additional and unique feature of the CT-afferents is that the response of the individual afferent is not as consistent and predictable as with individual Ab- afferents but may vary from one test series to the next for no obvious reason."
Well, maybe it has to replenish its supplies via internal transport mechanisms.
"The response features of the CT-afferents as out-lined above all converge toward the interpretation that the system is not designed to code accurately and consistently intensity and time course of skin deformations. These are functions which are essential for discriminative touch."
And C's are anything but discriminatory.
In daily life, the tactile system continually captures details of temporally and spatially variant skin deformations. As a result we can readily perceive more complex features, for instance, the direction of a stimulus moving along the skin and we can discriminate the intensity of component indentations which are closely adjacent in time and space to assess shape and surface structure of objects. Altogether, it seems evident that the CT-afferents lack response properties required for serving discriminative touch."

The chapter goes on for a couple pages discussing what they might be good for. Then:
"It may be asked why evolution has retained a separate system of unmyelinated afferents for social- emotional touch. Why could this role not be handled by the Aβ-afferents? It is difficult to deny that they could – and, in fact, they do in the glabrous skin of the hand. A particular reason for preservation of the CT-system is that unmyelinated afferents are parsimonious because they take up little space in the peripheral nerves."
OK, they're no trouble to keep because they're so small. Then interoception is discussed and I found myself quite fascinated:
"In a wider perspective, the CT-system may be regarded as a branch of a large afferent system which is basically concerned with your own body rather than external events, as conjectured by Craig. The basic role of the interoceptive system is to continuously watch the condition of body tissues, as well as physiological and chemical variables within the body. Interoceptive afferents have particular access to brain centers which control affective, hormonal, autonomic, and behavioral responses with effects to readjust adverse conditions and keep variables within desired ranges. The ultimate aim would be to keep the cell, the individual, and the species going. 
"Included in the interoceptive system are afferents related to perception of pain, itch, temperature, air hunger, vasomotor flush, hunger, thirst, and a range of visceral sensations, as well as afferents which are essential for the subconscious control of physiological variables, such as blood pressure and concentration of blood gases.
"The peripheral afferents of the interoceptive system consist of small diameter nerve fibers (thin myelinated Aδ and C fibers) with projections to the superficial lamina of the dorsal horn in the spinal cord and nucleus of the solitary tract. In this context it is interesting that touch sensitive unmyelinated afferents (C-LTM) have been shown to project to lamina I and II in several mammalian species, consistent with the interpretation that they belong to the interoceptive system. However, apart from this finding, connectivity studies of CT-afferents or homologs in other species are unfortunately lacking altogether in the literature. 
"At higher levels the small fiber afferents are tightly linked to amygdale and hypothalamus and, at cortical levels, to the insular region, primarily the posterior and middle parts. Moreover, there are indications that the anterior insular cortex on the nondominant side constitutes a still higher level housing a re-representation of the interoceptive image of the entire body. This representation of the physical self is postulated to constitute a basic foundation of mental consciousness.
Wow. Could this be part of the "body-self neuromatrix" proposed by Melzack? Hmmnnnn !
"The role of the CT-units as an afferent branch of a system guarding the well-being of the body would be to signal pleasure and reassurance as you are close to your parents, lover, kin, or friends. There are indications that pleasant bodily contacts promote hormonal responses, that is, endorphin and oxytocin, which contribute to the feeling of well-being, confidence, and calmness."
It would behoove us to recruit these in manual therapy if we could.

Then it gets really interesting, because the discussion steers toward grooming:
"Although the affective touch hypothesis implies that the particular role of the CT-system is to promote emotional, hormonal, and behavioral responses to pleasant physical contact with conspecifics, it is obvious that a number of other sensory channels are important as well. Interesting observations of social and biological roles of tight bodily contacts in non- human species have been reported. 
"A particular kind of bodily contact is grooming. At first sight it appears that grooming has a hygienic role alone. However, Dunbar has demonstrated in monkeys that it has an affective and social role as well. Obviously, the groomee is very pleased with the procedure even though the handling is often quite tough.
Well, tough grooming would have to be VERY well-managed in my opinion, as a human primate social groomer..
"Grooming increases the production of endorphin in the groomee. Dunbar has also found that monkeys spend much more time in grooming than required from hygienic point of view. It is particularly interesting that the time spent on grooming is larger, the larger the social group. The bottom line conclusion is that an essential role of grooming is to promote affectionate attachment between individuals and hence to keep the group together. The caring pattern of the mother in handling her young infants has a profound influence on the development of the child. Epidemiological studies in man have demonstrated that adverse conditions in early childhood tend to increase stressful and nonsocial behavior in the adult. Biological mechanisms that might be significant for this phenomenon have been explored in rats by Meaney and co-workers. 
Grooming in rats:
"Individual rat mothers differ with regard to caring pattern. Some are very active, spending a lot of time licking and handling their pups. Others are more passive in that respect. The caring pattern has a profound effect on epigenetic mechanisms related to the expression of stress hormone receptors in the brain. In the end, the offspring of active mothers become less stress sensitive, more curious, and exploratory than the offspring of passive mothers. Interestingly, these differences are permanent and remain in the adult, although they are partially modifiable. 
"Although it remains to be explored to what extent the CT-system is involved in affective response to bodily contacts in a social context, like grooming and mother’s care of her baby, there is no question that the CT-system is activated in these situations. The affective touch hypothesis implies that the CT-system is one of several communication channels accounting for responses to bodily contacts which engage perceptive, hormonal, autonomic, and behavioral mechanisms and might range from immediate pleasure, joy, and reassurance in sex to the post- natal development of your children’s stress coping profiles."
All very very basic information, all within the last 25 years or so.

So, back to The Skin as a Social Organ, last sentence in the introduction: 
"Touch also influences developmental pathways: maternal licking of rat pups can influence the behavior of the adult rat (Menard et al. 2004), and monkey infants deprived of tactile contact with a mother or mother surrogate become stressed and even ill-nourished (e.g., Harlow 1958). Here, however, we focus on primarily nonsexual, positively hedonic forms of interaction between adult humans, while acknowledging that these may have sources in and links with sexual and maternal touch behavior." 

Menard JL, Champagne DL, Meaney MJ (2004) Variations of maternal care differentially influence ‘fear’ reactivity and regional patterns of cFos immunoreactivity in response to the shock-probe burying test. Neuroscience 129:297–308 
More about high lick versus low-lick rats and their brain responses to electric shock.
Harlow HF (1958) The nature of love. Am Psychol 13:335–346

The Harlow link goes to a wonderful link containing images of animals caring for their babies (like the one above), and classic studies that were conducted on baby monkeys deprived of maternal contact who clung to cloth mother mannequins for kinesthetic solace.

Next up, the section, Touch in affiliative behavior and communication

Thursday, August 22, 2013

The Skin as a Social Organ: Part 1a: Touch can be pleasant, rilling.

The paper, The skin as a social organ

Previous introductory blogpost to this series.
Preamble: Random thoughts on spas

Part 1: Dual nature of touch: as PTs, do we "get" this?

The second and third statement in the abstract are really pretty self-evident. Aren't they? 
The second statement: 
"However, the research emphasis on these wide-ranging functions of touch leaves out a very essential fact: touch can also be pleasant." 

This is like a news flash to lots of manual therapists. They may well be touchphobes themselves (and if they are, who cares), but there is no excuse for ignoring this important information, clinically. Not when you're licensed to touch people, clinically. People who are in pain.
The third statement:
"This aspect of tactile sensation is at the heart of the social domain, allowing positive hedonic experience ranging from the reassurance of a pat on the back to the rills of a sensual caress."
Wasn't sure what a "rill" was. Thought maybe it was a Swedish word lost in translation. Or that somehow the word "thrilling" had been misspelled.
I looked it up, just to be sure, and... oh. my. gosh. It means some part of the landscape eroded by water, I think..  
(Look out, we may be in for yet another voyage, this time downstream.) 

Here is a picture of rills that caught my eye:

Rills on a cliff edge
They're lovely things, rills... they add texture to landscape. 
But rills can also be deliberately fashioned. I used to dig rills as a child, little drainage ditches with a toy shovel to carry meltwater away from the barn. My dad would nod his approval at my industrious efforts. 

I won't ever be able to go back to being a person who doesn't know what a rill is or what it means. Way more poetic than "neurotags"... don't you think? 

Apparently rills can be created in the brain by sensual caress. But probably any sort of well-intentioned touch in a carefully constructed context can do it, make metaphorical rills. As practitioners, let's not make any nociceptive rills. Let's not reinforce any that already are nociceptive. 

Next paragraph, only a few sentences long, but filled with a pile of references. 
Here we go, one sentence at a time:

"It is possible that functional divisions in the neural organization of touch may resemble that of pain, possessing two major, dissociable dimensions (e.g., Rainville et al. 1997; Hofbauer et al. 2001; Kulkarni et al. 2005; Auvray et al. 2008)." 
Rainville P, Duncan GH, Price DD, Carrier B, Bushnell MC (1997) Pain affect encoded in human anterior cingulate but not somatosensory cortex. Science 277:968–971 (Full text)
Hofbauer RK, Rainville P, Duncan GH, Bushnell MC (2001) Cortical representation of the sensory dimension of pain. J Neurophysiol 86:402–411 (Full text)
Kulkarni B, Bentley DE, Elliott R, Youell P, Watson A, Derbyshire SWG, Frackowiak RSJ, Friston KJ, Jones AKP (2005) Attention to pain localization and unpleasantness discriminates the functions of the medial and lateral pain systems. Eur J Neurosci 21:3133–3142 
Auvray M, Myin E, Spence C (2008) The sensory-discriminative and affective-motivational processing of pain. Neurosci Biobehav Rev. doi:10.1016/j.neubiorev.2008.07.008 (Full text)

 Wow, that is huge. I used to think that when I touched somebody on my treatment table I was touching their brain, all right, but only exteroceptively. Then I learned about C-fibres in skin whose job was to transmit pleasant input (from this group). We can touch peoples' interoceptors too! 
Next sentence:

"The sensory-discriminative dimension supports spatial localization and intensity encoding of a stimulus, and the motivational-affective dimension is involved in coding its valence (e.g., pleasantness/unpleasantness) and motivational relevance. So far, only a handful of studies have explored the possibility of a similar functional dissociation in the domain of non-painful cutaneous sensation (McGlone et al. 2007; Lovero et al. 2009)."
McGlone F, Vallbo AB, Loken L, Wessberg J (2007) Discriminative touch and emotional touch. Can J Exp Psych 61:173–183 
Lovero KL, Simmons AN, Aron JL, Paulus MP (2009) Anterior insular cortex anticipates impending stimulus significance. Neuroimage 45:976–983
Goodness, I shall have to hunt all these down, crack them open, take a look-see. For sure, that Lovero paper will be interesting. I think my anterior insular cortex tries to run my whole life. And she's very touchy. And by touchy, I mean picky.. 

"Though discriminative aspects of touch have been well-studied, the affective aspects have only recently been conceptualized and investigated in the neuroscientific literature (Essick et al.1999; Francis et al. 1999; Olausson et al. 2002; McGlone et al. 2007; Olausson et al. 2008a, b; Gallace and Spence 2008; Lovero et al. 2009; Löken et al. 2009; Guest et al. 2009)" 

Essick GK, James A, McGlone FP (1999) Psychophysical assessment of the affective components of non-painful touch. Neuroreport. 10:2083–2087 
Francis S, Rolls ET, Bowtell R, McGlone F, O’Doherty J, Browning A, Clare S, Smith E (1999) The representation of pleasant touch in the brain and its relationship with taste and olfactory areas. Neuroreport 25:453–459 (Full text)
Olausson H, Lamarre Y, Backlund H, Morin C, Wallin BG, Starck G, Ekholm S, Strigo I, Worsely K, Vallbo A˚ B, Bushnell MC (2002) Unmyelinated tactile afferents signal touch and project to insular cortex. Nat Neurosci 5:900–904 (Full text)
(This Olausson 2002 paper made my insular cortex go through the roof when I/we first laid eyes on it, about a decade ago.. 
"There!" it said, ".. there - do you believe me now!!??" 
"Yes," I replied. "Yes, I believe you.")
McGlone F, Vallbo AB, Loken L, Wessberg J (2007) Discriminative touch and emotional touch. Can J Exp Psych 61:173–183  
Olausson H, Wessberg J, Morrison I, McGlone F, Vallbo A (2008a) The neurophysiology of unmyelinated tactile afferents. Neurosci Biobehav Rev. doi:10.1016/j.neubiorev.2008.09.011 
Gallace A, Spence C (2008) The science of interpersonal touch: an overview. Neurosci Biobehav Rev. doi:10.1016/j.neubiorev. 2008.10.004 
Lovero KL, Simmons AN, Aron JL, Paulus MP (2009) Anterior insular cortex anticipates impending stimulus significance. Neuroimage 45:976–983 
Löken LS, Wessberg J, Morrison I, McGlone F, Olausson H (2009) Coding of pleasant touch by unmyelinated afferents in humans. Nat Neurosci 5:547–548 
Guest S, Essick G, Dessirier JM, Blot K, Lopetcharat K, McGlone F (2009) Sensory and affective judgments of skin during inter- and intrapersonal touch. Acta Psychol (Amst). 130:115–126

OK, two posts in one day, AND I got work done on the presentations. Not bad. I don't feel overly guilty now.

One more paragraph in the introduction, coming up next time. 

The Skin as a Social Organ: Part 1: Dual nature of touch: as PTs, do we "get" this?

The paper, The skin as a social organ
Previous introductory blogpost to this series.

Preamble: Random thoughts on spas

The first paragraph of the introduction is as follows:
"The sense of touch helps us to discriminate the location of a stimulus on the skin surface, to explore objects haptically, and to identify and manipulate objects. It also contributes to an integrated sense of our own body (see Serino and Haggard 2009). However, the research emphasis on these wide-ranging functions of touch leaves out a very essential fact: touch can also be pleasant. This aspect of tactile sensation is at the heart of the social domain, allowing positive hedonic experience ranging from the reassurance of a pat on the back to the rills of a sensual caress."
You really think this wouldn't need to be spelled out so clearly, yet, when I look at what my profession has become, what its human primate social grooming has turned into, I can totally see the point of how necessary it is to be firmly explicit on this: Touch says things to brains. Brains soak up all sorts of impressions from touch. Be kind. Have kind touch. 

The first reference goes to: 
Serino A, Haggard P (2009) Touch and the body. Neurosci Biobehav Rev. Volume 34, Issue 2, February 2010, Pages 224–236.

I found the authors. 
Andrea Serino is in Bologna, Italy, in the Department of Psychology. His research focuses on 
"multisensory integration, with special interest for visuo-tactile interaction; representation of body space and peripersonal space; relationship between tactile sensation and body representation; plasticity of spatial representations due to experience; brain plasticity following brain lesions and cognitive rehabilitation; rehabilitation of hemi-neglect with prism adaptation; rehabilitation of cognitive deficits following traumatic brain injury."
I don't know if ALL these papers are to do with him.. a quick search yielded 1750 results. There may be more than one guy with the same name publishing.. but if it is this one guy, he has published or co-authored 87 papers this year alone. Rather prolific, to say the least.
Wow. That is just one guy. 
There is an absolute TON of research out there on how the brain puts its inputs together. 

As therapists, even if we are physical, we should at least know this kind of research exists. No? 

Maybe we should even read some of it, some day, instead of being overly reductive in our so-called "science," too biomechanical, trying to re-invent the wheel by shaving even more of it away until it's square and won't even roll. 
(By me, Aug 22/2013. No copyright)
My point is, there are rafts of research on how the nervous system takes care of itself and its own organism just fine. We don't have to turn our profession into a huge make-work project. Or if we do, we could do it an easier way. 

Yet, I suppose it's necessary to test all these assumptions even if only to show that they don't work. Not when facing an opponent as wily as pain. 

But I digress.



The other author is Patrick Haggard. He works at Institute of Cognitive Neuroscience & Dept. Psychology at University College London. Assuming Pubmed knows the P. Haggard I'm talking about, the list of papers he has contributed to comes to 245, not too shabby. His list of research interests include "Voluntary action. Motor cognition. Touch. Somatosensation. Self-representation"

Pretty succinct list, vast amount of room to manoeuvre. 

Anyway, let's take a peek at the paper itself, Touch and the Body, at least the abstract. 
Abstract"The dual nature of touch has long been understood. The sense of touch seems to carry information at the same time about the external object touching our skin, and also about our body itself. However, how these two interact has remained obscure. We present an analytic model of how tactile information interacts with mental body representations in the brain. Four such interactions are described: the link between the body surface and the maps in primary somatosensory cortex, the contribution of somatosensory cortical information to mental body representations, the feedback pathway from such higher representations back to primary tactile processing in somatosensory cortex, and the modulation of tactile object perception by mental body representations."
Goodness me. 
Look how complex simple touch is. Just in this one abstract, 4 interactions right inside the brain of the person being touched!

Dual nature. Information about an external object and the body itself, being touched. Exteroceptive input and interoceptive input, from a single touch. 
That's huge, right there. 


Here we are, the profession most accepted as therapists who touch people. Why are we not grounded from day one in information like this? Yeah.. I know. There is only so much time, curricula have to be delivered,  exams prepared, students taught, exams corrected, people who are considered "safe" (or at least not overt hazards) cranked out into the world every few years with a license to touch people. 

Yeah. I get it. The world needs us, or at least people like us. I just wish we were cranked out better prepared to handle actual alive awake people with pain, not merely prepared to jiggle joints, stretch limbs, worry about posture, biomechanics, etc., as if they were the primary problems.. They are just nervous system output. They aren't really "things" to be "fixed" the way we are encouraged/brainwashed to think of them. 

Shouldn't we be given glimpses of this situation? What are we? Aren't we being sheltered as a profession from the very information that could, if we let it, turn us into better kinder more comprehending therapists? Make us more ... therapeutic maybe? 

OK, rant over for now.

Next, back to The Skin as A Social Organ, second sentence. 

EDIT: Back in to add a link to a blogpost by Kenny Venere, REDEFINING ‘EVIDENCE’ IN EBP: WHY “IN MY EXPERIENCE” DOESN’T CUT IT. His reference list is extensive and fabulous. His post points out (in the literature!) everything I was trying to say in the cartoon I built, about how useless square wheels are. 

Tuesday, August 20, 2013

The Skin as a Social Organ - preamble: random thoughts on spas

The paper, The skin as a social organ
Previous introductory blogpost to this series.

Let us begin with the abstract:
"In general, social neuroscience research tends to focus on visual and auditory channels as routes for social information. However, because the skin is the site of events and processes crucial to the way we think about, feel about, and interact with one another, touch can mediate social perceptions in various ways. This review situates cutaneous perception within a social neuroscience framework by discussing evidence for considering touch (and to some extent pain) as a channel for social information. Social information conveys features of individuals or their interactions that have potential bearing on future interactions, and attendant mental and emotional states. Here, we discuss evidence for an affective dimension of touch and explore its wider implications for the exchange of social information. We consider three important roles for this affective dimension of the cutaneous senses in the transmission and processing of social information: first, through affiliative behavior and communication; second, via affective processing in skin–brain pathways; and third, as a basis for intersubjective representation."
Preamble, random thoughts
I have always thought that as human primates, we have relegated social grooming to mostly symbolic activities, like hair dressing and childrearing and pet ownership. For whatever reason, maybe a prudish attitude, we marginalized social grooming for stress reduction off into the edges of human social existence. I'm speaking as a North American, of course.. we don't have much tradition here: everything that could possibly be medicalized has been medicalized, and if it isn't "medical" then it's "alternative." If it's "alternative" then it isn't "medicine," not scientific medicine, anyway.

Here, spas are places where rich women (usually women) (rich by overall planetary standards) go, spend big bucks to be wrapped in fluffy dressing gowns, have their nails done, hair done, faces done, and maybe a massage, maybe some unwanted hair removal, all the while listening to piped-in tinkly chime or else flute muzak. Spas here might sell stress reduction, but don't kid yourself, they are mainly businesses that exist to make money; they do not exist to attract or accommodate the general public of all ages the way free or low cost spas or springs do elsewhere in the world.

Health spas have a long history, all over the world. Spas are completely cross cultural. They existed long before modern medicine, i.e., somehow the human species found ways to hold itself together given the complete dearth of modern scientific medicine prior to the 20th century. Not that I'd ever want to go back to the bad old days before nice clean surgical repairs for busted appendix and other things that could and did kill lots of people, but... just this: I yearn for there to be a respectable place for this sort of wellness-centered care and attention here on the North American continent. A place for humans to gather and feel socially connected on the outside, while feeling completely enhanced on the inside, both at exactly the same time. Unfragmented. Indigenous. I can't think of anything else, on earth, that would help one feel that close to heaven.

I can see it.. how could it not be a wonderfully restorative experience?
Old Roman spa in the UK
Anywhere hot water bubbled up from the planet, it makes sense that people would gather there, to soak away their problems, or talk about and solve them - dis-solve them. Maybe they hired the locals to wrap them in hot mud cloths, scrape them off later with carefully nuanced stone scrapers. Massage them with oil. Let them soak in the springs again after. How could anyone still feel stressed after spending all day at a spa? Used appropriately, in a properly boundaried fashion, how could spa attendance not be health-preserving, health-maintaining?

[Edit: A twitter contact sent me this message: "North Africa has the wonderfully civilized Hammam which is a weekly tradition for everyone young and old" and this link to a blogpost about a spa in Morocco, "The Public Hammam – as experienced by a female member of staff…"]

(There is a long spa tradition in Sweden, apparently: I like to imagine that the authors of this paper are familiar with the local spas, and attend regularly to relieve themselves of all the stress associated with publishing papers.)

Spas developed a bit of a reputation over time. Too bad. Ruined it for any of us who descended from immigrants who had cheerfully escaped to leave it all behind.

I became a PT.
European (and maybe British, to some extent) physiotherapy grew out of elements of the spa tradition. Certainly massage therapy did. Something in me has always yearned for sensible, above-board repackaging of physical human contact for well-being - human primate social grooming. I've always been interested in providing human primate social grooming as a way to spend life productively on my way to exiting it at the other end, and going back to the exact same way I was before I was ever born. I managed to get there, wherever "there" is. Papers like this one really massage my confirmation bias, I've got to say.

Next, the introduction, and looking up some references, one of my second favourite things to do in the whole world.

Sunday, August 18, 2013

The Skin as a Social Organ 2010

The paper, The Skin as a Social Organ.

I don't have much time to do a big long open-ended blogpost series about this paper, the way I did with Melzack and Katz 2013, dragging readers along a metaphorical river voyage through trial and tribulation, for months, in order to better understand the neuromatrix model of pain, all the way into Melzack's "head"waters. 

But I sure would like to. 

Maybe some day I will. 

It will have to be ... well, not right now, because I have to prepare a new presentation these days, and another new one for in the spring, and I'll be busy flying all over the place teaching workshops then recovering from the effort, all fall. So this project will have to wait. Or else be done at a much slower rate, not the burst of a post almost every day, the way I did with M and K. 

OK, I can do this. Bits and dabs.
(This will probably require more discipline than the full blast way I wrote about the M and K paper.)

The paper I want to tackle, savour, sink into, saturate myself with, is "The Skin as a Social Organ" by India Morrison, Line S. Löken, and Håkan Olausson. (Luckily, a full pdf copy of it floats around loose in google; here is a link to that, so readers might read it themselves.) 

This is a delicious paper. It contains every reference to everything I think is important to life as a human primate social groomer. It's as though this paper was made for, written especially for, people just like me, and I want to thank the authors for making manual therapy and neuroscience come together in such a lovely, lovely way. It explains, well, mostly explains, what goes on in the brain and nervous system of a person who is being socially touched. The authors even comment extensively on grooming itself. Fabulous. 

I plan to go extract all the references and keep them in a special folder, savour them also. 

I have at least a year left before I lose my access to the library. I must use my access very efficiently and extensively while I still have it. Hang on folks - we'll be going on a very long and probably very broken up journey to the far corners of the brain in this blog series. 

First, let's meet the authors. 

Håkan Olausson
Professor Håkan Olausson

It is hard to find pictures of him. This one is the only one I could find. 

Håkan Olausson has been at this line of research, finding out all about what C fibres can do, (besides nociception, which is all most people think of when they think of C-fibres!) for a long time. I remember googling something about skin and touch more than a decade ago and bam! up popped the first paper I'd ever seen by him, which happened to be open access just then. It was Unmyelinated tactile afferents signal touch and project to insular cortex. (Psst! Here is a full text pdf floating around on google.)

Here is a whole list of full text papers he or his group have produced

It turns out Olausson worked at McGill for a time. Coincidence! 

His thesis was on "Human tactile directional sensibility." Gee. I wrote about that somewhere on this blog in the past. Over a year ago! Here is the post,  Dermoneuromodulation: Ruffini sensory endings and dorsolateral prefrontal cortex, March 2012. (I really should clean up, organize this blog someday. While I'm wandering around in its depths though, here is another post from a year and a half ago, with a lovely picture of a sensory neuron from an unrelated source: "Sensory neurons are the brain's portal to the external world.")

But I'm already digressing.

The next author is Line Sofie Löken. I think this is a woman. She is even more reclusive than Olausson, hard to google up anything about her. Here is a list of her papers, on pubmed.

India Morrison

India Morrison has been more prolific, her name associated with a list of 269 papers. Much less reclusive too, judging by the ease with which I found this picture of her.

There are many more researchers in this group, and maybe there is something in the water over there in Sweden, but anyway, I love their papers and all the implications therein for human primate social grooming that is pleasant and non-nociceptive. No way should people who are already in pain have to be afraid that their well-meaning therapist will give them more. No way should any well-meaning therapist have to deliver more nociceptive input.

The pleasant sensation fibres focused on in this paper are C-fibres, which means they synapse in the dorsal horn, with some other second-order "yes-ciceptive" neurons; then they cross over midline, take the spinothalamic tract up to the same parts of the brain that nociceptive neurons do. Once up there, the brain will consider yes-ciceptive input along with any other kind (noci-, or thermal, or just mechano-), will develop a strategy based on it, will form a representation of it, and will decide what sort of brain juice to make and squirt down into the spinal cord from that well-stocked drug cabinet it has in its brain stem.  

No one should have to hurt anyone to help them get over pain; that is completely unconscionable.

More to come, I guess.

Saturday, August 10, 2013

Melzack and Katz, Pain. Part 20: Conclusion

The paper, Pain.

Part 19: Implications of the Neuromatrix concept - phantom pain Part 19bImplications of the Neuromatrix concept - low back pain. Part 19c: Implications of the Neuromatrix concept - fibromyalgia


Congratulations, everyone who stuck with this exercise - we have reached the end!!

Have you ever felt trapped by your own limited understanding of something? Then a paper appears? And you decide you are going to chew down on it, until maybe something finally sinks in?
I wanted to fathom Melzack's vast understanding of pain, or at least try to. His new paper with Katz, Pain, has been the boat we've sailed in, all the way up the river, all along.

A way to move forward suddenly appears, framed by limited understanding. 

I like to think it took us up into Melzack's brain, right into his headwaters. Yes, the metaphor is clunky, but I like it.

So, who cares?
Well, life is still a mystery. Most people enjoy life passively; they float relaxed along the river of their own life, arms and legs draped over their own inflated inner tube of contentment or complacency, right out to the end of it, then out into the ocean of who-knows-what, upon dying.
At least, that's how it looks.
There nothing inherently wrong with that.
Life can, however, also be about asking questions and carefully considering answers, putting in some effort, traveling up the river instead, to find out where the questions arose in the first place. The answers might change, or new questions might arise.

A lot of science also looks like people just going with the flow.
Once in awhile, though, you see someone like Melzack turn around and go upstream and surmount hurdles to learn where the questions come from, and maybe find answers, maybe not, maybe just more questions. This makes life way more interesting.
I don't conduct any science, but I do enjoy watching it, and I admire everyone who has mapped new territory, or come up with new questions.
My own life has been about treating people in pain, so, pain is something I'm acutely interested by, which is kind of like swimming upstream in lots of ways.
I became fascinated by Melzack, by his model. It is brilliant, the way it puts a person with pain squarely in the middle of their own situation, gives them locus of control. It is brilliant, the way it gives clinicians like me the means by which I can hand to the patient sovereignty over his or her own body, and then do my job, which is to assist and support and be a consultant. 

Melzack had to move against the current and portage around rapids and waterfalls. He was no doubt bumped by legions of researchers all floating along in the conventional direction. But he knew the answer wouldn't be found at the ocean; what he examined convinced him that the model itself had been wrong, all along. So he decided to change the course of the river instead.  To do that he had to travel to his own headwaters, first - he has left a map that others can use if they want. He has shown the world of pain science, and the world of those of us who treat people with pain, a new way to think about pain.

Now, as an ordinary human primate social groomer, I've got to say, also, it's not easy to go against that massive deluge of papers all built on the model of pain being an input. You have to be a salmon and go upstream, against the current. So we did try, and hey! we made it! If we can make it to headwaters, then probably anybody can.

Let's revisit each of the four conclusions Melzack reached, that convinced him it was high time to let go of Descartes' ideas on pain and move to a new model, one that considered pain from all the angles that the old model simply ignored or couldn't account for.
Each represents a kind of headwater.
Here they are, once again, from blogpost 10 in this series:
"First, because the phantom limb feels so real, it is reasonable to conclude that the body we normally feel is subserved by the same neural processes in the brain as the phantom; these brain processes are normally activated and modulated by inputs from the body but they can act in the absence of any inputs. 

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.  
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.  
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."


What are headwaters?
They are simply the places where rivers begin.
Headwaters aren't fancy or impressive, most of the time.. they're small. They are where water collects and drips into puddles and becomes stream. They depend entirely on gravity and gradients to be able to flow, and grow. If they can converge, flow and grow faster than evaporation can take their constituents back up into the air, then, my friends, we have ourselves the start of a river, perhaps one that can become mighty some day.

The abruptly appearing kind

Headwater fens
Maybe Melzack's question and his conclusion about phantom limb pain started this way. Abruptly. Like a metaphorical whack on the side of the head. Maybe he suddenly realized, huhthe brain generates its own experience of being in a body. We don't need a body to feel a body


The kind that don't look like anything at first

Some headwaters are so small you could miss them entirely. They're just a wet spot on some ground somewhere.
Headwaters of  the Colorado River
Maybe this is a visual metaphor for what Melzack means when he says, Your brain, not your body, tells you what you're feeling.  Anything your senses can tell you, your brain can also tell you. 

You wouldn't have a clue this was the Colorado River if you didn't know from the caption and the link. The meaning-making part of your brain tells you it's river. Not your senses. By the same token, you can imagine the word "river" and have all the associations of "river" arise instantly in your brain, including an image of the Colorado River, specifically. [I.e., I'll never be able to get this fabulous picture out of my head, ever.] 


The more easily recognizable kind 

Some headwaters are distinct and beautiful; already a "river," small, maybe, but vigorous and impressive. 

Headwaters of the Roaring Fork River (also Colorado)
This is my visual metaphor for Melzack's third conclusion, that there is unity of body and self, against the outside world. Even if it is only just an illusion.


The gradually accumulating kind

Some headwaters look like just sloughs, wetlands. Not impressive-looking, but still, absolutely full of thick, rich potential.

Headwaters of three salmon rivers

Maybe Melzack's consideration of genetic specification that leads to a unique neurosignature is like this kind of headwater. Genetics result in a mushrooming of potential into actual. Epigenetics record interaction of that physicality with its environment over a lifespan. Genes are small but their "product" grows over time. Melzack says, in the brain are networks of cells, perceiving mechanisms, that already exist and expect certain inputs, are built to match them with temporally appropriate, timed outputs, which together comprise a body-self that exists to recognize and learns to protect itself. It is easily manipulated, dislocated, however. The brain generates its own experience of being in a body. 
We don't need a body to feel a body. 


Here is the last section of Melzack and Katz's wonderful review paper, the section titled Conclusion:

"We have traveled a long way from the psychophysical concept that seeks a simple one-to-one relationship between injury and pain."
We sure have.  Thank you for that, Dr. Melzack.
"We now have a theoretical framework in which a genetically determined template for the body-self is modulated by the powerful stress system and the cognitive functions of the brain, in addition to the traditional sensory inputs."
Yes. It's a lovely stretchy concept that will stretch to hold whatever pain science manages to throw at  our society from now on. It has room enough for everything that could possibly come down the chute at it. It's useful to everyone - not the least, those of us who work with live conscious people eager for information and willing to take on being head of their own team, subjects with a vested interest in overcoming something very personal to them - their own pain. Why? Because it includes them as part of their own recovery! It doesn't set them or their pain apart in a third-person way as an "object" to be "fixed" by a "specialist." That never worked very well anyway... see history of pain science, all of part 6. 
"The neuromatrix theory of pain—which places genetic contributions and the neural-hormonal mechanisms of stress on a level of equal importance with the neural mechanisms of sensory transmission—has important implications for research and therapy."
Yes it does.
"An immediate recommendation is that interdisciplinary pain clinics should expand to include specialists in endocrinology and immunology."
Yes. Clearly pain includes input by other systems in the body (maintained homeostatically by other parts of the brain) as well as a nervous system directly sensing and modulating itself.
"Such a collaboration may lead to insights and new research strategies that may reveal the underlying mechanisms of chronic pain and give rise to new therapies to relieve the tragedy of unrelenting suffering associated with needless pain."


We have reached the end of this blog series. Thank you, anyone who stayed with me for the whole ride. Now, it's time to .... 


OCTOBER 13/ 2013:
(Happy Thanksgiving, everyone in Canada..)
I've popped back into this series to add a link, without with I do not think this blog series would be complete. I don't know when it was published, but I want to include it for sure: 
It contains forty pages of comments by researchers acknowledging the man's contributions to pain  science, even if they were on a different tangent than he was/is.

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 Part 10e: The neural network that both comprises and moves "Self" is (only)modified by sensory experience

Part 11: We 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!

Part 12: Action! 12b: Examining the motor system, first pass. 12c: Motor 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 12g: The Action-Neuromatrix

Part 13: Pain and Neuroplasticity Part 13b: Managing neuroplasticity

Part 14: Side trip out to the periphery! Part 14b: Prevention of pain neurotags is WAY easier than cure Part 14c: PW Nathan was an interesting pain researcher  Part 14d: Brain glia are from neuroectoderm and PNS glia are from neural crest Part 14e: The stars in our headsPart 14f: Gleeful about glia Part 14g: ERKs and MAPKs and pain Part 14h: glia-fication of nociceptive input 14i: molecular mediators large and small Part 14j: Neurons, calling glia (over, do you read?) Part 14k: Glia calling glia, over. Do you read? Part 14l: satellite cell and neuron cell body interactions, and we're outta here!

Part 15: Prevention of neurobiological hoarding behaviour by dorsal horn and DRG glia is easier than clutter-busting after the fact

Part 16: Apples are to fruit as cows are to animals as nociceptive input is to pain

Part 17: The stress of it all Part 17b: Stress and adrenals Part 17c: Women, pain, and stress Part 17d: Stress, aging, and pain Part 17e: Stress and aging, keeping hippocampal dendrites fluffed up Part 17f: Chrousos and Gold and stress Part 17g: Stress conceptualization through the agesPart 17h: Phenomenology and physiology of stress Part 17i: Pathophysiology of stress Part 17j: cortisol, good or bad? Sensitivity to pain traumatization.

Part 18: Multiple determinants of pain