The Role of the Brain in relation to Pain

Pain perception

                     The Complex Homunculus



There is a representation or map of every body part in the brain. Consider this the ‘virtual representation’. The correct term for this representation is a homunculus. These virtual bodies inform us of what our ‘actual’ bodies are doing in space.

Above are 2 homonculi, 1 representing the skin and the other representing movement. In the sensory homunculus you will notice the areas in the brain devoted to the lips, hands and face are larger. This indicates that areas which require better sensation have a larger representation. The same is said for the motor homunculus as areas which you use more have a bigger representation. Again this is adaptable depending on your line of work, hobbies etc. For example an author will have a bigger representation of their dominant hand due to writing with the hand a lot.

Chartered Physiotherapy

                      Smudging & the Homunculus

Imaging studies reveal that chronic pain results in changes in the virtual representation of the area affected. ‘Smudging’ of the virtual limb so that there no longer is a clear defined outline of the body part is one such change. This can result in an overlapping of neighbouring body parts. I like to compare this to driving in a fog. When driving in fog your vision is compromised, no longer are you sure of what is ahead on the road- you become very cautious and hyper-vigilant in an attempt to control the environment -you slow down, turn down the music, you may even roll down the window. The brain is similar when unsure of what exactly is happening in an area- it can become very conservative in its management at times causing the neighbouring areas to hurt or areas that didn’t hurt before can start to hurt.

The more chronic the pain is, as in the longer you have been experiencing the pain then the more advanced changes in the brain have occurred. For example the more difficult that body part will be to use or the more sensitivity you will have in that body part or the neighbouring areas. Ultimately, the physical body mirrors the state of the virtual representation in the brain.

The great news is that smudging is reversible. Educated movement is excellent in helping to normalise the virtual representations in the brain. Every time you move in a pain-free controlled manner it is positively reinforcing normalisation of smudged representations. Furthermore, it is the understanding why pain occurs and removing the threat of the pain which enables you to move freely. This reason alone is why so much emphasis is placed upon the biology of pain and understanding the science behind this marvellous process. By gifting ourselves with this knowledge we are allowing ourselves to increase our physical capacity, reduce pain and improve quality of life.

‘Explain Pain’ by Lorimer Moseley and David Butler is a brilliant book which has formed the basis of these blogs. It is written with the aim to enable individuals who experience chronic pain. I would highly recommend it.

Should you require any further information on this topic of pain please do not hesitate to contact me in Personal Health on 01 4964002.