iSAW 02.04 Read it, Read it, Homunculus News

Brain Sense 101
Let’s continue to explore the “Explain Pain” concept of David Butler and Lorimer Moseley. The brain contains 100 billion neurons, 25% of them are mirror neurons, and 80% percent of the brain cells are glial cells with an immune function and intricate relationships with the other neurons. This provides about 200,000 kilometers of wiring superhighway. The brain can be impaled by a knife and generate no pain and yet a migraine can render us useless. Stunningly, Butler says that the brain replaces itself every few weeks. There is an interesting band of neurons in the sensory cortex running from the top of the head to just above the ear called the homunculus (little man). It performs like a sensorimotor contour map (see pic). Notice how some body parts are magnified like the lips, fingers, tongue and genitals. These parts also have a high number of sensory nerve endings and transmit large amounts of afferent information when injured, as I’m sure you can identify with. On the other hand the trunk, shoulder or the leg are seen as having less brain space represented.

The brain’s orchestra – the ‘neurotag’
Now it gets complicated. What are the determinants of whether to amplify noxious input, thus creating pain, or to inhibit it? These various parts of the brain include the cingulate cortex (focusing), amygdala (strong emotions), sensory cortex (discrimination), motor cortex (organize movement), pre-frontal cortex (problem-solving), hippocampus (memory), cerebellum (movement), thalamus (autonomic stuff) and not to be forgotten, the spinal cord (ascending facilitation or descending inhibition). The word ‘neurotag’ can be likened to an orchestra for pain. We can generate slow or fast, quiet or loud, solo or combined, emotional or flat, in-tune or discordant responses?

Positive change and smudging
As well as determining pain, the neurotag can also protect us. If we’ve had a nasty event happen someplace, every time we pass by we will have a memory of it; maybe even a shudder or twinge of pain. The alarm system has just had a trial run. We will be extra careful. The homunculus is ever-changing. Braille users enlarge the finger part of their homunculus. It can also go wrong. A violinist with shoulder pain may have a distorted representation of her virtual shoulder in the brain. This is called ‘smudging’ and is an overlapping or blurring of the image. The more chronic the injury the more advanced the changes in the brain.

Conundrums and solutions
The parts of the homunculus that have less sensory activity are the ones that seem to have the most chronicity, like the low back, the shoulder, the neck. Are these body parts more easily smudged? Can we solve chronic cases by improving or sharpening the body image, i.e. ‘homuncular-refreshment’? Can we use mirror neurons to help us do this? At the 360 NMT clinic we are using Explain Pain to reeducate the mind of the patient by explaining that damage and pain are poorly correlated and that hurt does not always equal harm. We also change their pain perception by changing the meaning and context of it. For body interventions we use tools like multi-stimulating distractions, non-threatening new movements that are carefully graded and paced (baby steps), and bodywork that reassures and reacquaints the sufferer with a sharper (less smudged), and therefore safer virtual body image.