The Physiology and Psychology of Pain




shutterstock_163572803

Pick up any newspaper and pore over it. Not only are nations at war but communities in the same country are fighting amongst themselves. People are killing each other for a piece of land, money, or just because they hate a person who looks different from them or worships another God. In the midst of these gory tales of hatred are the stories of triumph — men and women who give up their lives to save others and doctors who put their lives in the line of fire to treat people in far-flung places and war-torn regions.

Why do some people hurt others while others live just to bring a smile on other people’s faces?

Why do some people cause so much pain to others while some dedicate their lives to heal the wounds of strangers?

According to scientists, the perception of pain in oneself and recognizing it in others (empathy) is influenced by the complex interplay of neural circuitry in the individual, biochemical reactions in his brain, societal conventions, and evolutionary mechanisms.

The Perception of Pain in Self

Physical pain has a distinct brain signature. Functional magnetic resonance imaging (fMRI) can evaluate the amount of pain. However, another study has built on these findings to suggest that people “feel” physical pain differently. This difference stems from the way their brains are wired.

According to one recent study, the experience of pain has two distinct neural stages or pathways. The first stage kicks off, say, when you accidentally burn your fingers or cut your hand. The nerves in your hand send signals to the brain. The pain stimuli reach parts of the brain, like the anterior cingulate cortex, that are associated with the perception of pain. The chain of events that make up this stage is similar in all healthy individuals.

But people “react” differently to pain; not everyone utters an “ouch” or reaches out for a painkiller when they are physically hurt. The researchers who took part in the above study now know why. They have discovered a second neural pathway instrumental in the perception of pain. The “feeling” of pain — mild, intense, or unbearable — is determined by the activity in the medial prefrontal cortex and nucleus accumbens. These two regions of the brain are conventionally associated with motivation and emotion.

Scientists now know there are definite emotional and cognitive underpinnings to the perception of pain. This indicates that individuals can regulate and/or alter their perception of pain through mental conditioning techniques like meditation, distraction, and visualization. People who suffer from debilitating pain, triggered by a disease or an injury, can now hope to find relief in coping mechanisms other than popping painkillers.

The Societal Context of Feeling Pain

The perception of pain has a societal basis as well. Several studies have found that individuals tend to report different levels of pain in presence or absence of a highly-empathic person, like a romantic partner, and a complete stranger. Women tend to report less pain in the presence of an “attachment figure” or someone who makes them feel safe. In an experiment, women subjects in a threatening situation showed greater activity in the region of their brains that triggers safety signals (that is, they felt less pain) when they were shown images of their romantic partners.

One study, however, clarifies that the perception of pain in such cases is actually determined by the attachment style of the subject.

Individuals with anxious attachment styles crave close and intimate relationships but tend to sacrifice their needs to keep their partners happy. They are not confident about their partner’s affections and fear the relationship will not last. According to the findings from the above study, women with this attachment style tend to feel more pain in the presence of a person who does not empathize with their conditions. They feel lower pain in the presence of their romantic partners who are perceived to be highly empathic.

Individuals with avoidant attachment styles tend to value independence and self-sufficiency more than intimacy. These people are not comfortable sharing their feelings with strangers and partners alike. So it is not surprising that studies indicate that women with such attachment styles report lesser pain when alone than when in the presence of another individual, who may be a stranger or a romantic partner.

With these findings, doctors may now need to think twice before they ask individuals to be present when their partners are giving birth. It seems that there is no rule of thumb.

The Perception of Pain in Others

Human beings are social animals. The ability to live harmoniously in a society, care for others, and form enduring relationships depends on the quality of empathy. So it is natural that scientists should be curious to know why some people are more empathetic than others or if some situations naturally bring out more empathy.

Scientists believe that empathy is triggered by various cognitive and affective processes. Few years ago a study was carried out on subjects with congenital insensitivity to pain (CIP) to understand if painful experiences from the past influenced the ability to empathize with the pain of others. People with CIP cannot feel anything when subjected to painful stimuli. So they have no “experience” or memory of pain. But curiously, as was found in the study, they can empathize with the pain of others by seeing and hearing pain-related behavior in video clips.

But do you think that emotional cues of pain like seeing groaning and writhing are so powerful that they can move one and all? Unfortunately, no. Empathy is more complex than that.

A new article published this year reports that human beings tend to be more empathetic towards friends than strangers. The study also noted that stress tends to affect the ability to empathize. Individuals who are under stress tend to be less empathic to the pain of strangers than when they are relaxed and peaceful.

The latter finding may explain mob violence or why violence tends to increase during social uprisings. Stress is a powerful trigger that can make people act in a way they would not think about in other situations.

The mechanisms underlying empathy are complex. But it is crucial that scientists delve more into them because it seems that understanding empathy is akin to decoding violent behavior. And the world could certainly do with a lot less violence!

References

Danziger, N. (2006). Is pain the price of empathy? The perception of others’ pain in patients with congenital insensitivity to pain Brain, 129 (9), 2494-2507 DOI: 10.1093/brain/awl155

Decety, J. (2011). The neuroevolution of empathy Annals of the New York Academy of Sciences, 1231 (1), 35-45 DOI: 10.1111/j.1749-6632.2011.06027.x

Eisenberger, N., Master, S., Inagaki, T., Taylor, S., Shirinyan, D., Lieberman, M., & Naliboff, B. (2011). Attachment figures activate a safety signal-related neural region and reduce pain experience Proceedings of the National Academy of Sciences, 108 (28), 11721-11726 DOI: 10.1073/pnas.1108239108

Krahe, C., Paloyelis, Y., Condon, H., Jenkinson, P., Williams, S., & Fotopoulou, A. (2015). Attachment style moderates partner presence effects on pain: a laser-evoked potentials study Social Cognitive and Affective Neuroscience DOI: 10.1093/scan/nsu156

Martin LJ, Hathaway G, Isbester K, Mirali S, Acland EL, Niederstrasser N, Slepian PM, Trost Z, Bartz JA, Sapolsky RM, Sternberg WF, Levitin DJ, & Mogil JS (2015). Reducing social stress elicits emotional contagion of pain in mouse and human strangers. Current biology : CB, 25 (3), 326-32 PMID: 25601547

Sambo, C., Howard, M., Kopelman, M., Williams, S., & Fotopoulou, A. (2010). Knowing you care: Effects of perceived empathy and attachment style on pain perception Pain, 151 (3), 687-693 DOI: 10.1016/j.pain.2010.08.035

Wager, T., Atlas, L., Lindquist, M., Roy, M., Woo, C., & Kross, E. (2013). An fMRI-Based Neurologic Signature of Physical Pain New England Journal of Medicine, 368 (15), 1388-1397 DOI: 10.1056/NEJMoa1204471

Woo, C., Roy, M., Buhle, J., & Wager, T. (2015). Distinct Brain Systems Mediate the Effects of Nociceptive Input and Self-Regulation on Pain PLoS Biology, 13 (1) DOI: 10.1371/journal.pbio.1002036

Image via Tyler Olsen / Shutterstock.

Viatcheslav Wlassoff, PhD

Viatcheslav Wlassoff, PhD, is a scientific and medical consultant with experience in pharmaceutical and genetic research. He has an extensive publication history on various topics related to medical sciences. He worked at several leading academic institutions around the globe (Cambridge University (UK), University of New South Wales (Australia), National Institute of Genetics (Japan). Dr. Wlassoff runs consulting service specialized on preparation of scientific publications, medical and scientific writing and editing (Scientific Biomedical Consulting Services).
See All Posts By The Author

Do not miss out ever again. Subscribe to get our newsletter delivered to your inbox a few times a month.