Ouch! The Neuropsychology of Pain
14th June 2023
Written by JJ Wellock, Assistant Psychologist.
Have you ever wondered why it is that sometimes you can be walking around with a cut on your finger and not feel it? It is only when you realise it is there that suddenly it may as well be falling off. Well, hold on to your finger’s folks, we are about to talk science!
Let us start with immediate pain, like when you stub your toe off the corner of a table for example – yep, ouch! Near the surface of your skin and around your organs, muscles, and bones, we have a sensory neuron called a nociceptor or a free nerve ending (Dubin & Patapoutin, 2010). They are highly sensitive to mechanical, chemical, and thermal threats, and play an important part in keeping us alive (Smith & Lewin, 2009).
Nociceptors have a minimum threshold which need to be met before they start sending electrical messages to the brain (otherwise known as an action potential) (Dubin & Patapoutin, 2010). This message is then passed through your nerves, spinal cord and into the thalamus of your brain, where it is transmitted to other areas, such as the prefrontal cortex (Krummer et al, 2020), for interpretation. The severity of the pain perceived is dependent on the frequency that the nociceptors are activated, the type which has been activated (Tracey, 2017), and the level of cognitive engagement at the time (Legrain et al, 2013).
Once your brain has decided it warrants a response, it sends a signal back out to relevant areas of the body. With noxious stimuli, a signal is sent instantly via the motor nerves to the site of injury to prevent further damage (Smith & Lewis, 2009). In the case of the stubbed toe, it makes you hop around cursing yourself. In some cases, prostaglandins are released to encourage inflammation as a protective mechanism (Riciotti & FitzGerald, 2011); as well as Endorphins which act as a natural painkiller to help ease discomfort (Hartwig, 1991).
Going back to the finger cut that you haven’t noticed. Studies have shown that the brain can suppress nociceptor signals when it is engaged in more demanding tasks (Legrain et al, 2013). If you’re busy running around the house trying to think about what to pack for a holiday, for instance, you may not notice that you accidentally caught yourself on the edge of something sharp because you are cognitively engaged in something more important at the time. It is only when you become conscious of it, that the brain suddenly changes its priority.
Interestingly, pain can also be felt even without nociceptor input. A famous case published in the 1995 British Medical Journal was about a construction worker who jumped onto a plank and impaled his boot on a 7-inch nail (Fisher et al, 1995). He was in such pain, that he needed to be sedated. However, when they removed his boot, the nail didn’t even scratch the surface of his skin and had instead gone between his toes. Further studies have therefore found that pain can be a psychological experience, even in the absence of noxious stimuli (Loeser & Melzack, 1999).
By understanding the relationship between nociception and the subjective experience of pain, we can implement techniques for managing it such as distraction (Rischer et al, 2020) and mindfulness (Majeed et al, 2018).
Standby for further blogs on chronic pain, and the effectiveness of hypnobirthing .
If you are suffering from chronic pain and would like some help, or for further reading, please see the below links and references:
The Pain Toolkit:
NHS – How to get help
https://www.nhs.uk/live-well/pain/how-to-get-nhs-help-for-your-pain/
Pain Concern – Helpline
https://painconcern.org.uk/helpline/
References:
Dubin, A. E., & Patapoutian, A. (2010). Nociceptors: the sensors of the pain pathway. The Journal of clinical investigation, 120(11), 3760-3772.
Fisher, J.P., Hassan, D.T., O’Connor, N. (1995). Minerva. BMJ, 310, 70
Hartwig, A.C. (1991). Peripheral beta-endorphin and pain modulation. Anesth Prog, 38(3), 75-78.
Kummer, K. K., Mitrić, M., Kalpachidou, T., & Kress, M. (2020). The medial prefrontal cortex as a central hub for mental comorbidities associated with chronic pain. International journal of molecular sciences, 21(10), 3440.
Legrain, V., Crombez, G., Plaghki, L., & Mouraux, A. (2013). Shielding cognition from nociception with working memory. Cortex, 49(7), 1922-1934.
Loeser, J. D., & Melzack, R. (1999). Pain: an overview. The lancet, 353(9164), 1607-1609.
Majeed, M. H., Ali, A. A., & Sudak, D. M. (2018). Mindfulness-based interventions for chronic pain: Evidence and applications. Asian journal of psychiatry, 32, 79-83.
Ricciotti, E., & FitzGerald, G. A. (2011). Prostaglandins and inflammation. Arteriosclerosis, thrombosis, and vascular biology, 31(5), 986-1000.
Rischer, K. M., González‐Roldán, A. M., Montoya, P., Gigl, S., Anton, F., & van der Meulen, M. (2020). Distraction from pain: The role of selective attention and pain catastrophizing. European Journal of Pain, 24(10), 1880-1891.
Smith, E. S. J., & Lewin, G. R. (2009). Nociceptors: a phylogenetic view. Journal of Comparative Physiology A, 195, 1089-1106.
Tracey, W.D. (2017). Nociception. Current Biology, 27(4), R129-R133