Pain is Perception and not Sensation.
The International Association for the Study of Pain defines the word pain as: “An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” (International Association for the Study of Pain, 2018; Merskey and Bogduk, 1994).
To have a better comprehension of the experience of pain, it is necessary to introduce the term ‘nociception’, which, is described as the neural activity in charge of transmitting sensory information from noxious stimuli through afferent signals. It is noteworthy that although nociception is — most of the time — the principal cause of pain, it can not be accepted as a synonym of the latter (Iannetti and Mouraux, 2010; Legrain et al. 2011; Mischkowski et al. 2018). To further highlight the difference between these terms, it is necessary to note that brain’s response to nociception can be provoked without resulting in pain; moreover, pain can be elicited by non-noxious stimuli (Legrain et al. 2011; Mischkowski et al. 2018).
This essay is going to focus on how pain can be categorized as perception and not as a sensation. To achieve this, we must first understand what perception and sensation mean, and how these two words are differentiated from one other. The definition of ‘perception’ is: “The process by which an organism detects and interprets information from the external world by means of the sensory receptors” (Dictionary, 2020). Although similarities with the definition of pain and the definition of perception can be already noticed, a deeper analysis is required to negate a connection between sensation and pain. The sensation is seen as the response to external stimuli by our sensory organs, it is the pure transmission of data without any kind of elaboration or interpretation by the Central Nervous System (Privitera, 2020).
From the definition of perception and sensation we have just seen, it is deducible that perception refers to something interpreted by the single organism; consequently, every organism will have a different perception of an event from another one. The remainder of this essay will consist of a discussion on how the experience of pain can change from one person to another; thus displaying, through an inductive approach, how pain can be labelled as perception and not as a sensation
Why pain can be modified by non-noxious stimuli, and how.
Various studies show how pain experience can be mutated by the attention, emotions, predictability and other factors (Clark et al. 2008; Linton and Shaw, 2011; Mischkowski et al. 2018). Furthermore, it has been demonstrated how social rejection and empathy for pain can activate the same areas of the brain involved in the elaboration of noxious stimuli and that part of nociceptive-specific neurons respond to non-noxious inputs such as a threatening visual stimulus (Iannetti and Moureux, 2010). Consequently, it has been affirmed that the pain matrix (a group of areas of the brain involved in the elaboration of noxious signals) works on a multimodal approach (Iannetti and Mouraux, 2010).
How emotions can modify the intensity of pain.
Emotions are one of the strongest factors that may influence the experience of pain. Linton and Shaw (2011) state that “emotions are powerful drivers of behaviour and shape our experience of pain via direct neural connections”. Negative emotions such as anxiety, fear, guilt and depression lead to an amplification of painful events; indeed, depression can also elongate the duration of pain from musculoskeletal injuries (Linton and Shaw, 2011). Moreover, during a 2008 study conducted by Clark et al. on how anticipation of pain can modify the perception of it, it is interesting to note that people have claimed to prefer a quick but painful stimulus, over waiting for a weaker one. This reaffirms how anxiety and attention have an impact on what we feel.
However, the emotion which can majorly influence pain is fear. In fact, fear influences the attention process, inducing ‘hypervigilant’ behaviour; for instance, threatening information can help stimulate catastrophic thoughts about pain. (Linton and Show, 2011). Pain catastrophizing is defined as “an exaggerated negative orientation about pain where a relatively natural event is irrationally made into a catastrophe […], making treatment more difficult and increasing the risk of developing persistent pain and disability.” (Linton and Shaw, 2011).
How experience can modify the intensity of pain.
Another factor that has a strong influence on the perception of pain is past experiences. In 2011, Linton and Shaw wrote that: “previous events have the ability to shape the reaction and the perception to painful stimuli, defining pain as a subjective experience”.
Experience can also stimulate pain catastrophizing, triggering anxiety and depression, which, as we mentioned before, lead to a hypervigilance state increasing the perception of pain. A clear explanation of this chain is the fair-avoidance model (Picture 1). The fear-avoidance model shows how an experience of injury can ignite panic at the first sign of pain, intensifying the amount of pain felt (Linton and Show, 2011).
However, the experience can also decrease the intensity of pain: in fact, when a stimulus is continuous and stable a person may stop paying attention to it; this is an event known as ‘sensory adaptation’ (Privitera, 2020). Having said that, we cannot completely ignore pain or get rid of it, as the aim of nociceptive signals is to acquire attention. (Iannetti and Moreaux, 2010; Linton and Shaw, 2011; Privitera 2020).
How beliefs and expectations can modify the intensity of pain.
Two additionally strong factors capable of reducing the intensity of pain are beliefs and attitudes towards a subject: what a person believes, provides an automatic response to painful experiences (Linton and Shaw, 2011).
Research undertaken at Oxford University demonstrates how religious belief may help with the pain. The project involved two groups of people, atheists and Catholics. MRI scans showed how the brain was reacting to electric stimuli. It was reported that Catholics felt 12% less pain compared to agnostics after seeing the picture of the Holy Mary. The researcher noticed that in the Catholic group, the MRI scans showed activity in a part of the brain that might have an effect on the elaboration of pain. (NHS, 2008; Jamieston, 2008; Sample, 2008). However, beliefs might also lead to an amplification of pain intensity. For instance, if a person with a sore knee believes that the soreness is provoked by a broken bone, the anxiety and fear experienced will lead to an amplified pain intensity (Linton and Shaw, 2011).
Interesting also is the connection between beliefs and expectations. Expectations may also be a reason why the intensity of pain can vary between different subjects: for instance, if someone expects to heal from an injury in a time that is shorter than the true healing period, they may fall in a depressive status after those unrealistic goals are not achieved (Linton and Shaw, 2011).
How diseases can modify the intensity of pain.
The last factor to address is diseases. There are many pain-related diseases; one example is hyperalgesia, defined as: “Increased pain from a stimulus that normally provokes pain” (International Association for the Study of Pain, 2018; Merskey and Bogduk, 1994). In other words, hyperalgesia is an increased response to pain as a result of past injuries or from the use of painkillers: something that would cause a low-intensity level of pain will now be experienced as moderately to intensively painful (Seladi-Shulman, 2017).
A further example of the pain-related issue is something similar to hyperalgesia: allodynia. Allodynia “ was originally introduced to separate from hyperalgesia and hyperesthesia, the conditions seen in patients […] where touch, light pressure or moderate cold or warmth evoke pain when applied to apparently normal skin.” (International Association for the Study of Pain, 2018; Merskey and Bogduk, 1994). As the International Association for the Study of Pain wrote in 2018, Allodynia refers to pain induced by stimuli that in normal condition would not provoke pain.
The conclusion from point 2.
According to my argument above, we can conclude that the experience of pain can be labelled as subjective; indeed, it is based on various factors, including emotions, experiences, religious beliefs, expectations and diseases.
Definition and explanation of perception.
Understanding the definition of “perception” stated in the introduction, an interesting word to be considered is “interpretation”. If one focusses on a square chair, everything we perceive about it is that it has a square shape. Even when standing further away from it, we will still perceive the chair as square, ignoring the fact that we clearly see a rhomboid shape. The reason why our interpretation of the visual stimuli result in a square shape comes from our past experience and our belief: because we know, and because we have experienced that the chair is squared, our brain will perceive the rhomboidal shape of the chair as a square. (Angell, 2007).
Having said that, we can affirm that our brain interprets stimuli using personal experience, memory, learning and emotion and consequently, perception may vary from one person to another. (Privitera, 2020; Lumen, no date).
Definition and explanation of sensation.
Throughout this essay, “sensation” has been defined as the “pure transmission of data” (Privitera, 2020), and thus, the difference between sensation and perception is made clear. To link sensation to pain, the transmission of noxious stimuli is known as nociception (Iannetti et al. 2010; Legrain et al. 2011; Mischkowski et al. 2018). Moreover, peripheral sensory neurons, also known as nociceptors, provide information to the brain, which — after having processed the information — might result in pain. (Dubin and Patapoutian, 2010). Consequently, as sensations are the pure information originated from stimuli, we can affirm that nociception is the sensation connected to pain.
Pain is a perception.
The introduction of this essay already marked that nociception can not be understood as a synonym for pain. The previous point stated that nociception is a sensation, consequently, we can confirm that pain cannot be defined as sensation.
My opening point in this essay described how pain can be influenced by such non-noxious factors as experiences, emotions, religious beliefs and diseases. Consequently, it can be confirmed that pain is subjective and may vary from one person to another. It has also been explained how perception may vary as well; and some factors that contribute to the interpretation of perception have been listed: experience, memory, learning and emotion.
As a final point, the similarities between perception and pain can now be elaborated: firstly, both pain and perception are subjective and they are influenced by the same factors, such as experiences and emotions. Following an inductive method, it is possible to state that: as both pain and experience are both subjective experiences influenced by psychological factors, pain is a perception (Streefkerk, 2019).
As pain is a perception, and nociception is a sensation, the validity of our thesis can now be confirmed: pain is perception and not sensation.
Conclusion.
This essay has sought to show how pain is a perception and not a sensation; the thesis has been firstly written in the introduction, then developed into the main body following an inductive method. Now that we know that pain is subjective, it is worth to do a reflection on how to link this statement to clinical practice.
Pain varies from one person to another; as a clinician cannot know if the patient is in pain through assessment, the therapist must trust the patient and respect their pain. Pain must not be underestimated, and must not be doubted by the clinician, as every pain experience is unique. Something tolerable for one person may be excruciating for another (Siebert, 2018).
Bibliography:
Angell, R. (2007) Psychology: An Introductory Study of the Structure and Function of Human Conscious. 3rd ed. New York: Henry Holt and Company. Available from: https://brocku.ca/MeadProject/Angell/Angell_1906/Angell_1906_f.html [Accessed 12.05.2020]
Clark A. et al. (2008) Dissociating nociceptive modulation by the duration of pain anticipation from unpredictability in the timing of pain, Clinical Neurophysiology, 119 (1), pp. 2870–2878. DOI: 10.1016/j.clinph.2008.09.022
Dictionary (2020) Available from: https://www.dictionary.com/browse/perception [Accessed 08.05.2020]
Dubin, A. & Patapoutian, A. (2010) Nociceptors: the sensors of the pain pathway, The Journal of Clinical Investigation, 120 (11), pp. 3760–3772. Available from: https://ncbi.nlm.nih.gov/pmc/articles/PMC2964977
Iannetti, G. & Mouraux, A. (2010) From the neuromatrix to the pain matrix (and back), Exp Brain Res, 20(1), pp. 1–12. DOI: 10.1007/s00221–010–2340–1
International Association for the study of Pain (2018) IASP Terminology. Available from: httpps://www.iasp-pain.org/Education/Content.asapx?ItemNumber=1698 [Accessed 07.05.2020]
Jamieston, A. (2008) Belief in God ‘really can relieve pain’, The Daily Telegraph. Available from: https://www.telegraph.co.uk/news/religion/3096743/Belief-in-God-really-can-relieve-pain.html [Accessed 12.05.2020]
Legrain V. et al. (2011) The pain matrix reloaded A salience detection system for the body, Progress in Neurobiology, 93 (1), pp. 111–124. DOI: 10.1016/j.pneurobio.2010.10.005
Linton, S. & Shaw, W. (2011) Impact of Psychological factors in the Experience of Pain, Physical Therapy, 91 (5), pp. 700–711. Available from: https://academic.oup.com/pti/article-abstract/91/5/700/2735743 [Accessed 08.05.2020]
Lumen: Introduction to Psychology [no date] Sensation and Perception. Available from: https://courses.lumenlearning.com/wmopen-psychology/chapter/outcome-sensation-and-perception/ [Accessed 08.05.2020]
Merskey, H. & Bogduk, N. (1994) Part III: Pain Terms, A Current List with Definitions and Notes on Usage, 2nd ed. Seattle: IASP Press.
Mischkowski, D. et al. (2018) Pain or Nociception? Subjective experience mediates the effect of acute noxious heat on autonomic responses, PAIN, 159 (4), pp. 699–711. Available from: https://journals.lww.com/pain [Accessed: 07.05.2020]
NHS (2008) Religious belief and pain relief. Available from: https://www.nhs.uk/news/neurology/religious-belief-and-pain-relief [Accessed 12.05.2020]
Privitera, A. (2020) Sensation and Perception. Available from: https://nopabroject.com/modules/sensation-and-perception [Accessed 07.05.2020]
Sample, I (2008) Religious belief can help relieve pain, say researchers, The Guardian. Available from: https://www.theguardian.com/science/2008/oct/01/medicalresearch.humanbehaviour [Accessed 12.05.2020]
Seladi-Shulman, J. (2017) Opioid-Induced Hyperalgesia, Healthline (Reviewed by Weatherspoon, D.), 23 August. Available from: https://www.healthline.com/health/hyperalgesia [Accessed 07.05.2020]
Siebert, K. (2018) Why physician should respect the pain patients report. Available from: https://kevinmd.com/blog/2018/05/why-physician-should-respect-the-pain-patients-report.html [Accessed 13.05.2020]
Streefkerk, R. (2019) Inductive vs. deductive reasoning. Available at: https://scribbr.com/methodology/inductive-deductive-reasoning [Accessed 13.05.2020]
Vlajen, JW et al. (2000) The fear avoidance model of musculoskeletal pain (adapted from: Vlaeyen JWS & Linton SJ) Fearavoidance and its consequences in chronic musculoskeletal pain. [Scheme] Available from: https://www.researchgate.net/figure/The-fear-avoidance-model-of-musculoskeletal-pain-adapted-from-Vlaeyen-JWS-Linton-SJ_fig1_7577433 [Accessed 11.05.2020]
