Pain is one of our most useful survival mechanisms. What you feel as pain, however, does not necessarily match up with what is happening to your body, because pain is – like everything we experience – ‘all in the mind’.
Sometimes, stubbing your toe lightly on a chair can make you cry out in pain, while at other times you can take a much harder knock and barely notice. When we are very busy or excited, even severe physical injuries may go unnoticed – in fact, just occupying yourself, with some mental tasks or sinking into a pleasant daydream can reduce pain considerably.
The reason you don’t notice pain when you are occupied becomes you have to pay attention to information coming in from the senses 111 in order to be conscious of it. Pain signals from nerves in the skin, joints and muscles enter the brain and are registered in the brain ‘s ‘ body map ‘ – the somatosensory cortex. But this does not automatically produce the experience of pain. For this to happen, another part of the brain must bring the signals to consciousness by directing attention to them. The area responsible is the frontal section of the cingulate cortex, which lies in the de e p groove between the brain’s two hemispheres. This acts as a switch, directing attention either to the outside world or to what is happening within the body. When it is activated, we become conscious of information – such as pain – in the somatosensory cortex; when it is ‘ off ‘ we are completely absorbed in whatever is happening in the world around us.
Neuropathic Pain
Sometimes we experience pain even when there are no pain signals coming in. This type of pain, known as neuropathic pain, is all in the mind ‘ – but it is not imaginary. Rather, it is a form of memory. It usually occurs in people who continue to feel pain even after an injury has healed. In this case, the original pain signals cause certain brain cells to fire together and then, over time, to ‘ wire’ together – the resulting firing pattern is the pain. Normally these links would fall apart when the pain signals stopped, but in neuropathic pain, the links remain etched in the brain, like any other type of memory. This sort of pain is often distressing because it seems to have no physical cause.
How pain helps us
Compared to the complicated brain processes that control pain perception, the ‘wiring’ that sends pain signals to the brain is relatively simple. There are two main types of pain fibre, both of which end in receptors that react to damaging stimuli like pressure or heat. Thicker ‘fast’ fibres carry signals from the receptors to the brain at high speed, producing a sharp ‘ warn ing’ stab of pain: this is the first thing you are aware of when you hurt yourself, and it alerts you to the injury. Narrower ‘slow’ fibres co n du ct signals at lower speed and cause the aching, throbbing pain that follows an injury, lasting for hours or even days. Once pain signals arrive in the brain, they pass to the amygdala, which acts as a relay station directing pain signals onto other areas.
Although pain is a useful warning system, once it has done its job of alerting us to injury, it ceases to be beneficial. Fortunately, there is no need for most people to suffer: mild pain can be helped by paracetamol, aspirin or ibuprofen, while severe pain can usually be controlled with the use of drugs such as opioids.
