A while back I wrote a piece about Consciousness and Pain, in which I argued that consciousness might be the key ingredient for pain. I even tried my hand at a bit of maths, with this little equation (not to be taken too exactly): pain = nociception + consciousness. I got a great response to this post. People had some really interesting points to add. While we all basically agreed that nociception—tissue damage/impending tissue damage—doesn’t necessarily cause pain, we couldn’t quite put a name on that ‘catalyst’, that other something that has to be there in order for pain to result. Is it consciousness? Or maybe awareness or attention?
There was one comment in there which I’ve been thinking about ever since, because it made me stop and think about the nociception bit first. I thought it was worth bringing to the fore and starting another discussion.
Tim (sorry to stick you in the spotlight!) said:
Just as we don’t have ‘pain receptors’, perhaps the notion of nociceptors imparts a judgement on the news of difference too early (that judgement being threat)…
Great point. What Tim is saying here, correct me if I’m wrong, is that we are already imparting a value on an incoming nociceptive stimulus by its very definition, “tissue threatening stimulus” or “an actual or potentially tissue-damaging event”… i.e. I am already aware, attentive, conscious of the fact that I may feel pain very soon because I just hit my thumb with a hammer! And we’re supposedly not even onto the second half of my equation yet…
If nociception IS NOT pain, that is if the former is incoming stimulus and the latter instead a complex experience, then why do these peripheral receptors have a special name at all? Admittedly nociceptors are high threshold; they do not respond to any stimuli that are not close to being dangerous to tissue. But maybe we should just stick with the tried-and-tested innocuous names—thermal, mechanical, chemical sensory receptors, and perhaps just stick a “high threshold” prefix in there for further clarification. After all, a lot of thermal, mechanical and chemical stimuli are “tissue threatening” or “actual or potentially tissue-damaging stimuli”. I guess it comes down the least confusing for all of us, and definitely the least likely to create panic and danger messages, for patients.
Flavia Di Pietro is a PhD student in the Moseley Group investigating the development of Complex Regional Pain Syndrome (CRPS) after wrist fracture. Flavia’s PhD focuses on the early detection of brain changes in CRPS using fMRI. But get this – Flavia did Physiotherapy Honours degree at Notre Dame and completely cleaned up – Brian Edwards Memorial Award, Physio Research Foundation Award, Dean’s Award. Now, these things mean that she is not only ticking the academic boxes but all the other fluffy stuff too. No surprises that the NHMRC of Australia jumped to support her PhD. So she has come over from Perth where she has been working as a physiotherapist. All her achievements, however, pale in comparison to her celebrated status as the best Shoe Salesperson south of Milano, as evidenced by her taking out the 2006 and 2008 Diana Ferrari Golden Boot Award. Clearly, she did not write this bio.
* One of the awards in Flavia’s bio is fictitious.
 Chalmers, D. (1995). Facing up to the problem of consciousness. J. Consciousness Studies, 2, 200-219.