BBC Horizon’s Secret World Of Pain

Last year BBC Horizon created a documentary entitled ‘The Secret World of Pain‘. I watched it on YouTube a week ago, thought it was really well put together and so decided to share the most salient points.

Pain is one of our most ancient survival mechanisms and it protects and alerts us to danger. The SCN9A gene is responsible for regulating electrical signals that send pain sensation to the brain. Certain rare genetic disorders can prevent people from feeling pain…these unfortunate people are much more susceptible to burns and other injuries…this underlines just how crucial the sensation of pain is to us.

Pain can alert us to injury or potential injury, but why doesn’t it reflect the extent of injury…and why is it so subjective? There are a couple of possible reasons for this. Key experiences in early life have been found to be as important to pain perception as genetics. Early life is crucial for the formation of pain pathways which are shaped in response to touch. For example, premature babies are exposed to a lot more painful procedures and this alters the normal development of their pain pathways…the overdevelopment of pain pathways makes them hypersensitive and much more likely to experience pain in the future.

Pain and pleasure are both perceptions…psychological constructs…and so environment, context, decision-making, attention, distraction, motivation, emotion, etc can change how signals are processed and hence influence pain. There is a limit to how much information the brain can process at any one time…focussing attention on something pleasant (distraction) decreases the brain’s ability to process pain signals.

Subjects in an experiment were shown a triangle and exposed to a low temperature which they rated as 3/10 on a pain scale…this was repeated several times…they were then shown a square and exposed to a high temperature which they rated as 7/10 on a pain scale…this was repeated several times…they were then shown the square but exposed to the low temperature instead…surprisingly they rated the pain as 5/10. The researchers concluded that anxiety had affected their sensation of pain. I would add that expectation and conditioning may also have played a part.

Chronic pain is pain that persists long after an injury has healed…and therefore serves no purpose. It affects 1 in 5 people and is one of the biggest medical health problems. It can become an enormous burden on the brain and leads to chemical and structural changes. MRI scanning has revealed that people with chronic pain have less grey matter in the pre-frontal cortex. The answer to chronic pain may lie in reversing these changes. Encouragingly, electromagnetic impulses to the brain cortex have helped to normalise changes and to decrease pain, albeit temporarily. Research into this sort of treatment is extremely promising but still in its infancy.