‘What is pain? (Danger is painful)’ – a contribution to our special edition collection of pain in the medical humanities, by Seamus Barker
The International Association for the Study of Pain defines pain as, ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’, but advances in our neuroscientific and behavioural understanding of pain now render this definition incomplete. A fuller definition of pain, grounded in the current neuroscience, suggests fascinating philosophical implications that are yet to be teased out.
Following the work completed by Australian researchers Lorimer Moseley and David Butler, which concords with my own experiences of working in Chronic Pain clinics for over a decade, I think pain is too complex to be reasonably understood as perceptual, representational, or primarily emotional.
Pain does not correspond to the sensory and affective experience of tissue damage, or even to the sensory and affective experience of the (accurate or not) perception of tissue damage (as perceptualist accounts from Philosophy of Mind might have it). Rather, I agree with Moseley and Butler that pain corresponds to the brain’s calculation of present danger to the body, in a richly evaluative and sometimes future-orientated way. I would go further and suggest that, for pain to occur, the brain must also calculate that such pain is part of the most adaptive response available to the organism to the calculated danger. Such calculations of danger usually (but not necessarily) draw on somatosensory information coming from nerves supplying tissue, but also – at a neurological level – on past experiences, thoughts, beliefs, and emotions. It is worthwhile emphasising that such activity occurs non-consciously and instantaneously, and so is usually elided from our awareness. That is, emotions, thoughts and beliefs are involved in the split-second calculation that precedes the brain’s production of a pain experience, rather than simply forming a background to an individual’s post hoc interpretation of their own pain.
These ideas are clearer in action. If we cut a finger, specialised nerves in tissue that respond to noxious stimuli signal tissue danger to the spinal cord and thence to the brain in a process called nociception. Yet, as Moseley and Butler note, nociception is neither necessary nor sufficient for pain. They point to a study in which subjects received an entirely sham electric shock. Half the participants in the study experienced pain, pain that increased proportionately to the sham dial on the “stimulator” being turned up. These subjects drew on the available information, in this case (misleading) verbal cues provided by the testers as to the nature of the experiment, as well as their own pre-existing beliefs and attitudes. For those subjects who experienced pain as the ‘stimulator’ was ‘turned on’, we can infer that their brains, or non-conscious minds, calculated that there was present danger and that experiencing pain was the most adaptive response. ‘Danger’ is preferred to ‘perceived tissue damage’ precisely because it is more evaluative, vague, and open to individualised distortion by attitudinal and belief-related factors; indeed, it is non-perceptual.
Another study also supports this idea. Women who experienced pain after mastectomy experienced more severe pain if they believed the pain was caused by returning cancer. In this case, increased pain seems linked to a calculation of increased danger to the tissues, and indeed to the whole organism, a complex evaluation so rich and future-orientated it seems silly to consider its conscious correlate – pain – as a ‘perception’ or ‘representation’ in any conventional sense of those words. In this instance, where peripheral nociception does seem likely to be occurring, it is worth mentioning that ‘descending pathways’ originating in the brain come down to meet second-order nociceptors at the spinal cord, outnumbering them in the order of a hundred to one, and functioning to excite or inhibit ascending nociceptive input. In this way, the brain routinely up-regulates or down-regulates nociception, an activity which accords with the idea that the brain calculates danger using all available knowledge, whether provided by somatosensory or contextual information, or from entrenched beliefs, and modulates the production of pain accordingly.
It is also useful to consider how individuals can experience tissue damage and nociception but feel no pain. Testimony from soldiers who have lost limbs in battle and yet felt no pain until they were safely off the battlefield is mentioned by Butler and Moseley; anecdotal reports from boxers suggest they similarly feel little pain until the match is over. In these instances, it seems that even if the brain calculates danger, if it also calculates that the most adaptive survival response is to not be distracted by pain, and to instead focus on escaping or fighting on, then no pain will be produced. Hormones like adrenaline and the descending inhibition of nociception are involved with such minimally painful experiences, but it is worth remembering that it is the brain, the non-conscious mind, that still must authorise such physiological processes, matching them to particular circumstances based on a range of highly personal and evaluative factors, appraised through what might be called a hermeneutic process.
This guest contribution is the first of two written by Seamus Barker, who has worked in Chronic Pain teams for over a decade as a Physiotherapist, and now coordinates the Persistent Pain Program for Ballarat Health Services in Australia. During that time Seamus has maintained a keen interest in the neuroscientific and behavioural bases of pain, and their philosophical consequences. Seamus completed a BA (Hons) at the University of Melbourne in 2012 and an MPhil in American Literature at the University of Cambridge in 2014. He plans to commence a PhD in 2015 in the Medical Humanities program at the University of Sydney, which will look at the consequences of the marked differences in the narratives provided by medical science, by the Medical Humanities, and by sufferers of chronic pain, as they answer the question: where is the pain is coming from?
Correspondence to Seamus Barker
You can follow Seamus on Twitter with @sbpainphysio
Works cited
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