Unlike a simple sense impression such as taste or smell, pain seems to be a fully-fledged, mind-body experience. We don’t just feel pain — we are gripped by it almost like an emotion or mood. How does that happen? Does pain always correlate with injury in the body? I’ll try and keep this short, and as jargon-free as possible!
Fancy a warm day at an idyllic beach. Wading towards the shore after a long leisurely swim, gazing around at the sunlight on the waves, you unexpectedly stub your toe on a submerged rock. Let’s use that example to analyze what’s going on as you suddenly find yourself dealing with a flurry of unpleasant feelings.
I know, you’re like noci… wha?? Jargon straight up! Don’t stress — I never heard this word until a couple months ago either. But this is the only jargon for the whole article, ok? Bear with me …
Roughly speaking, nociception is the name for the pain signal before it reaches the brain. Interestingly enough, nociception itself does not cause much of a reaction in the area where the injury happens.
In the case of your accident at the beach, it is not until your brain receives a signal from the toe, that any kind of response begins to take place.
Nociception vs Pain
When we get a signal that “something hurts”, how does that expand into such a rich experience that all or most of our concentration and our emotions are suddenly turned towards it?
Well, as soon as your brain receives the nociception signal it does some trickery to figure out how bad the damage is (if you just scratched yourself or if you cut yourself deeply). It also looks into where the signal is coming from and how easily damaged that area tends to be (if you stub your toe it hurts more than if you hit your arm).
You’re already starting to feel things in a context that is more than just simple nociception. Next up perhaps memories will crop up of the last time you stubbed your toe, you’ll lift your foot out of the water and examine it closely. Your eyes and visual parts of your brain will be processing all those images. If you’re like me you’ll be wondering if anyone has noticed and if you perhaps look a trifle silly standing on one leg in the water with your other foot held up in front of you. You’ll be trying not to topple over.
Our mind has gone from soaking up the summery day, to a more active state. After the initial fast signals, the toe is now sending slow throbbing nociception signals to our brain, and every time a new throb reaches our brain, it goes through that whole activation state again. It returns our focus to our foot from whatever else might be going on. Now we are experiencing pain.
What’s interesting is that nociception and pain can be experienced separately. While normally of course, nociception does lead directly to an experience of pain, in some cases it is possible to experience great amounts of nociception but to be in an entirely pain-free state. This is sometimes noticed in cases of “massive trauma”  by paramedics in victims at the site of a car crash.
The opposite is also possible, for example when “individuals with functional pain syndromes report considerable anguish in spite of having [no measurable -nociceptive activity]”. 
Pain as a Perception
These understandings and many more led Ronald Melzack, a Canadian who studied phantom limbs and pain, to refer to pain as an “output of the central nervous system”. (Ok, a tad more jargon. “Central nervous system” is a medical term for the brain and spinal cord.)
What Melzack is saying here is that although pain does start starts in the site of injury, it is not until it is taken into the central nervous system and evaluated as being important enough to warrant attention, that the pain begins to intrude on our thoughts and emotions. This is more like a perception, where we are not just receiving sensory input but thinking about it and evaluating it.
Although this may seem quite obvious, you can see that rolling all of this together and calling it “pain” turns pain from being a simple realisation that “something hurts” to being the full mind-body response to an incident of nociception, and not just the nociception itself. Linking it all together like this is the only way to explain complex pain syndromes like those outlined above, or in the case of a phantom limb causing pain, where the pain persists in the brain long after the nociception has ceased.
The particular brain regions that are involved in taking up the call of pain, on behalf of the nociception from the site of injury, in order to generate this “output” are many. Moskowitz identifies no fewer than sixteen different brain regions!  and  Many of these are connected with our emotions and our thinking patterns, and others are connected with our body’s most basic self-monitoring and survival systems.
This explains why pain can be such a distressing experience, and why we sometimes shrink away even from the thought of hurting ourselves. The emotional centres of our brain are anticipating our potential distress and creating aversive reactions before the pain has even happened, by simulating the pain independently of receiving any actual nociception.
I’ve found this knowledge to be the start of a whole investigation into the nature of pain. Knowing that pain is partly to do with how I evaluate it, and not just a result of being told “something hurts” by my body, has been quite an eye-opener for me.
I hope you’ve found it interesting too. If so be sure to like my Facebook page or follow my blog for more updates. I write about wellbeing and mindfulness, with a few creative pieces thrown in from time to time.
Here are some useful links I’ve found while reading about pain theory.
How do our brains process pain? contains a good introduction with some diagrams.
And there’s way more to be learned from this How Pain Works at HowStuffWorks.
 Melzack, Ronald. “Gate control theory: On the evolution of pain concepts.” Pain forum. Vol. 5. No. 2. Churchill Livingstone, 1996.
 Garland EL. Pain Processing in the Human Nervous System: A Selective Review of Nociceptive and Biobehavioral Pathways. Primary care. 2012;39(3):561-571. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438523/
 Moskowitz, Michael MD and Golden, Marla. Neuroplastic Transformation Workbook. pg10-13. https://www.amazon.com/Neuroplastic-Transformation-Workbook-Michael-Moskowitz/dp/0615814654
 Doidge, Norman. The Brain’s Way of Healing. Penguin Books 2016. pg 13-14.