Since I’m a used to be academic and a theory nerd I have taken time to really dig into the subject of pain research. I would like to provide you the basic theoretical insights I have gathered about the topic, if you’re not into theory you can just skip this section and wait for the next post.
What is pain? For a long time, pain was seen as a sensation produced by injury, inflammation or other tissue damage. This is the ’old’ – the Cartesian – understanding of how pain occur. Nociceptors – pain receptors in the tissue send information about damage to the brain and thus we feel pain. In this sense pain is a sound reaction preventing us from causing more damage by not moving or touching the place that hurts. This view, however, has come to be altered with progressions in pain research. We know now that pain is utterly complex and there is more to it then just the physical, structural aspects.
”While sensory input may initiate pain or other bodily awareness, it is not the sole, or even the dominant, causal mechanism” (Chapman 1996).
Physical pain is tackled from many different academic fields, such as neuroscience, psychology and physiotherapy. I also look into non research-based knowledge in the area of back pain; the topic has been adressed by alternative practitioners of therapeutic body techniques, such as yoga. Neuroscience, the science of the nervous system, focuses on nerves and nerve impulses, hence it concerns a rather high level of abstraction of the body. Physiotherapy, on the other hand, is more practice-based in its approach and concerns a lower abstraction level of the body. While the two fields produce different knowledge output, one is not more right than the other, they complement each other in a nice way.
There are two theories that really pushed forward our understanding of the causes of pain. The first one is the gate control theory from 1965. The neurologists Ronald Melzack and Patrick Wall showed, through a number of experiments, that non painful input closes the ’gates’ to painful input, thereby preventing pain sensations from travelling to the central nervous system (the brain and the spinal cord). So by creating other sensations in the body we may prevent the nervous reaction causing pain. It is generally believed that the gate control theory provides evidence of the psychological aspects of pain perception.
Ronald Walzack continued to work on the gate control theory, however, and later developed the neuromatrix theory of pain. Basically Walzacks insights came from studying phantom limb pain, reflecting on the fact that patients experience pain in a body part even though there is no body part there to feel. The neuromatrix theory of pain states that pain is produced by the central nervous system instead of the peripheral nervous system. Nociception, pain signals, travel from damaged tissue, via the peripheral nervous system, into the central nervous system. These are one part of what causes us to experience pain. The matrix, however, is made up of a network of neurons that consists of loops between the thalamus and the cortex, as well as between the cortex and the limbic system. Hence, pain is caused by this network, and by a characteristic pattern, the neurosignature, defining all the nerve impulses within the neuromatrix.
Does it seem a bit too complicated to grasp? In short it means that pain is in the brain more than in the body. Internal nerve impulses may be nociception – nerves sending signals about tissue damage. Nociception is an internal stimuli, it comes from within the body, just like an inflammation, a slightly irritable bowel, or stress. But nerve impulses in the neuromatrix comes from internal as well as external stimuli, that is, from changes taking place outside of our bodies as well as changes inside of our bodies. External stimuli could be we hear someone tell us we are strong, or weak, or maybe we read about someone having a strange and paralyzing disease that started out with a sore lower back. It could also be that we engage in some activity that we love to do and that makes us forget about the pain. Each part of the neuromatrix contributes to various aspects of the pain experience, the sensory, the emotional, the cognitive, motoric, behavioural, and conscious aspects of pain.
In short, pain is a nervous system condition rather than a structural, physical, condition. In the next post, I will look deeper into the causes of pain from a yogic perspective, how can we make sense of the complexity of pain and its connections to our general state of mind and all other things that provide inputs into the neuromatrix?