onsdag 1 juli 2015

Pain; mode d’emploi

Pain and pain avoidance are some of the fundamental mechanisms shaping us as persons. Pain is a tool in learning and a motivation for acting and reacting.
Pain is often accompanied with discomfort, but not always. Pain may amplify other sensations, give redemption, turn discomfort into pleasure and prime us for reward. Pain is the meter to which we measure our pleasure.

2014, the Norweigian scientist Siri Leknes published the review-article “Benefits of pain” which is an excellent overview over the psychological mechanisms explaining the useful functions of pain. If I don’t give a reference to a statement in this blogpost, it will probably be found there. All of this research is representative for random volunteers.

Pain as an amplifier of sensations

2004 a paper was published showing that a short, painful episode (a painful laser pulse) increased the brains response to “touch” (or actually, a short electric stimulation on the skin, resembling touch). The increased sensitivity, termed “pain-induced facilitation” was shown also apply to touch on completely different places on the body. Pain can be divided into phasic pain (less than 20 s) and tonic pain (more than 20 s). While phasic pain serves to alert the senses, tonic pain will decrease sensation to touch. Pain and pleasure are generally considered as mutually exclusive phenomenon: a sensation of pain prevents subsequent sensations of pleasure, while pleasure of some sort reduces the perception of pain. (Thus people experience intense pleasure may be very tolerant to pain and even injury…)
The pain-induced facilitation has also been shown to enhance taste and the ability to differentiate between different tastes.

Relief from pain is reward

The worse the pain is, the more relief you are going to feel when pain is relieved. This is intuitive. But also, the more scared you are of pain, the worse pain you anticipate, the greater the feelings of reward are when you have avoided the pain. Thus, the greater the contrast between expectation and outcome, the greater the relief. Leknes showed this using fMRI 2011. The feeling of reward (relief) of pessimists when the pain was not delivered was due to signalling in a small spot of the brain called nucleus accumbens (NAc).

How pain will reward us

The NAc is a long known hot-spot for reward-seeking and is essential for learning from painful experience. 2008 Leknes and Irene Tracey wrote a review article “A common neurobiology for pain and pleasure” for Nature. Here the authors describe how tonic pain (longer lasting pain) will trigger dopamine release in NAc, which in turn will stimulate the brain's own reward-system; opioids. Signalling particularly through the m-opioid receptor, MOR, increases the effectiveness of rewards. So, pain will release a burst of motivating dopamine and opioids, which do not only function to decrease pain but will activate us to seek reward and when we get it, feel more satisfied by it. Sustained pain will function pleasure-enhancing.
The ability of pain-induced opioids to enhance pleasurable reward may be a mechanism for why contrasting pain with reward may actually end up with netto increase in pleasure-gain from pain, in some situations. 

The hedonic flip – or the general theory of pain relativity

Siri Leknes and co-workers have also shown that the context of pain will determine if we at all perceive it as pain or pleasure. By contrasting a mild pain (defined as a mild pain on its own) to a stark pain, this made the mild pain be perceived as a pleasure! The very same pain that was uncomfortable when the alternative was absence of pain was suddenly registered as a pleasure when the alternative was a worse pain. This beautifully shows the discrepancy between the concept of pain and discomfort. Though often intermingled, these phenomenon are not synonymous. Pain in its objective sense does not necessarily need to be uncomfortable. Rather the opposite. Leknes is very careful to point out this discrepancy in her reviewarticle form 2014.

The guilt-trip

Scientists have come to realize what the catholic church has known for ages; pain can relieve guilt. By relieving us from an unpleasant feeling, pain allows us to return to a steady-state and this relief equals pleasure. However, the pain that relieves the guilt must stand in relation to the severity of the action that caused the guilt in the first place. Not only does pain relieve guilt in the person that suffers from it; it also provides redemption to the pain-receiver in the eyes of others.

Knowing about these mechanisms provide endless possibilities to extract pleasure from pain, which was the original purpose of this blogpost. However, it turned out to be more of a celebration of the scientist Siri Graff Leknes. She is truly worth that.