A recent study found that nearly 50 million adults in the United States experience chronic or severe pain, which is more than cancer and diabetes combined (American Pain Society, 2015). Another study indicated that chronic pain costs the US up to $635 billion (ScienceDaily, 2012). The problem of chronic pain in our society has become a national epidemic. Lorimer Moseley is a clinical and research physiotherapist as well as a Professor of Clinical Neurosciences and Chair in Physiotherapy at the University of South Australia, who has dedicated the majority of his research to investigating the role of the brain in chronic pain. In his Ted Talk entitled “Why Things Hurt”, Moseley artfully and comically shows that pain is designed to be a protective instinct that varies significantly depending on the context in which the pain is experienced. In order to illustrate this phenomenon, Moseley relates two incidents that happen in the same location under slightly different circumstances to show the powerful impact of simple environmental cues and past experience in generating the brain’s response to pain.
For example, imagine you are walking barefoot down a safe street on which you used to roam as a child, and you step on a piece of gravel. When the piece of gravel presses on the skin of your foot, somatic sensory receptors in your foot are activated and a message travels through large myelinated nerve fibers to the spinal cord and then to your brain. The brain is rapidly informed that there is danger on this particular injured area of your foot. Meanwhile, the injury also activates nociceptors, the axons of which are thin, unmyelinated slow-conducting nerve fibers that send the warning message only as far as the spinal cord. Spinal nociceptors then carry this same message to the thalamus of your brain. At this point, the brain evaluates the situation by calling upon its various regions to gain information about the current environment as well as memories related to that environment. Taking all of this into consideration, the brain then decides how dangerous the situation is, and a certain amount of pain is finally experienced as a result of how dangerous the brain concludes the situation to be. Thus, because your brain realizes that you are in a familiar and safe area, it produces an insignificant amount of pain in your foot and you carry on with your walk.
Now imagine that you’re on the same street, walking barefoot, but you have a vivid memory of being bitten by a venomous spider as a child in that same area. Suddenly, your foot steps on something and your brain jumps to conclusions. The message reaches your thalamus, which connects with your parietal cortex and frontal lobes to recognize the familiarity of the location and recall the severity of the previous spider bite incident. As a result, your brain perceives the situation as extremely dangerous, and you experience excruciating pain. However when you look, there is no sign of a spider bite, but merely a small scratch from a piece of gravel on the pavement. This misleading pain represents an illusion that the brain is capable of creating based on what it thinks is occurring to your tissues when you sustain an injury. An arm, or a leg, or a finger does not have the ability to produce pain, but the brain, and only the brain allows a person to experience pain as a protective response to danger. As Moseley states, “pain can be conceptualized as a conscious correlate of the implicit perception that tissue is in danger” (Moseley, 2007). Thus, as Moseley concludes, pain is, in fact, nothing more than an illusion.
But how, you might ask, does phantom limb pain fit into Moseley’s theory? It is a well-known phenomenon that many people who lose a limb experience pain in the amputated limb. In fact, there are other pain syndromes like chronic neuropathic pain, migraines and complex regional pain syndrome in which general cortical re-organization of neuronal fibers has been documented to explain these sensations (Moseley & Flor, 2012). The million-dollar question is why our brain would reorganize itself to continually experience pain. The logical conclusion is that it is trying to protect us. The nervous system has made a survival decision and concluded that there was a threat. If the brain thinks there is something that is persistently wrong, such as in an amputated limb, it will set the sensitivity of pain at a level that it perceives to be in your best interest to try and make you protect yourself. Even though there is no limb on the person’s body, that person’s brain is perceiving that his or her limb is in danger and creates the illusion of severe pain to get the body away from danger.
Moseley and his colleagues further exemplify the brain’s creation of illusory pain in a simple yet incredibly elegant study where participants’ hands were touched with a cold piece of metal while a blue or red light shown in front of them (Moseley, 2011). Despite the fact that the metal stimulus was the exact same for all participants, those participants who were shown a red light described their experience as significantly more painful than participants who were shown a blue light. This experiment thus provides additional evidence that pain cannot be described simply as a physiological reaction to what occurs in the body, as it clearly incorporates environmental messages, even as simple as an object’s color, into its processing of how dangerous a situation is, and thus the degree of pain that is experienced.
Chronic pain is evidently very complicated. It has been shown that there are cultural differences, gender differences, ethnicity differences and personality differences to the reception of pain (Jarrett, 2011). Cultural influences likely have neurobiological etiologies in that a person’s beliefs and values can impact and affect the way their body responds to pain stimuli. Thus a person’s culture can potentially influence pain through a psychological mechanism. For example, there are certain cultures and religious traditions that believe pain is important and needs to be experienced. Growing up with that belief and understanding would likely alter one’s cognitive interpretation of danger and thus influence one’s behavior and physiological response to the pain pathway.
Link to Larimer Moseley’s TedTalk: Click Here
American Pain Society. (August 18, 2015). NIH study shows prevalence of chronic or severe pain in U.S. adults. Retrieved from: https://www.sciencedaily.com/releases/2012/09/120911091100.htm.
Jarrett, C. (2011). Ouch! The different ways people experience pain. The British Psychological Society, 24, 416-420.
Moseley, G. L. (2007). Reconceptualising pain according to modern pain science. Physical Therapy Reviews, 12, 169-178.
Moseley, G. L. (November 21, 2011). TEDxAdelaide – Lorimer Moseley – Why things hurt. Retrieved from: http://tedxtalks.ted.com/video/TEDx-Adelaide-Lorimer-Moseley-W.
Moseley, G. L., & Flor, H. (2012). Targeting cortical representations in the treatment of chronic pain: A review. Neurorehabilitation & Neural Repair, 20, 1-7.
ScienceDaily. (September 11, 2012). Chronic pain costs U.S. up to $635 billion, study shows. Retrieved from: https://www.sciencedaily.com/releases/2012/09/120911091100.htm