Neuroscience of Chronic Pain
Overcoming chronic pain requires overcoming a brain problem. This artist’s conception, based on actual photos of human neurons from Morgane Audouard in Ken Kosik’s group, shows areas of the brain that are generating the experience of chronic pain being quieted by retraining the brain. A more detailed view of the brain structures that create the experience of chronic pain is here.
Recent breakthroughs suggest that intense chronic pain can be greatly reduced or even eliminated by training your brain. The only cost is effort! A 2016 Nature Communications article provides convincing scientific support for the ideas that have already helped thousands overcome chronic pain: specifically, that chronic pain is not just a result of signals from the body and must also be dealt with as a brain problem. Chronic pain can have a life of its own in the brain independent of input from the signals from pain sensors (nociceptors) in the body. The article [Woo] found a stimulus intensity independent pain signature-1 (SIIPS1) with multiple activated areas in the brain. It builds on related experimental work of other groups that had previously shown that chronic pain involves different brain areas than acute pain [Vachon-Presseau] [Hashmi][Baliki 2014]. It is consistent with recent theoretical work that describes pain as an emergent phenomenon related to activity in large-scale networks that include non-nociceptive regions [Kucyi] [Farmer].
The problem with the neurons firing together is that:
As neurons fire together they “wire together”, which means that it becomes easier and easier and for them to fire together in the same activity (for example, in creating the experience of pain).
Neurons will fire together and wire together even with no external input! This is demonstrated in work published in 2016 from Europe and Japan on human neurons grown in small dishes that contain Multi Electrode Arrays (MEAs). This work reveals that human neurons will fire spontaneously and excite each other into activity without any external stimulus! That is fine if they are in the small dishes just doing their thing. It is not fine if they are in your brain generating the experience of pain!
The photos of the MEA and human neurons above came from Morgane Audouard, Carolina Camargo, Jiwon Jang, and Ken Kosik, with whom I am privileged to collaborate. They have confirmed that human neurons will fire spontaneously and excite each other into activity without any external stimulus.
Further support for the need to deal with the brain problem in order to overcome chronic pain comes from a 2016 review in Science that stated: “Phenomena such as placebo analgesia or pain relief through distraction highlight the powerful influence cognitive processes and learning mechanisms have on the way we perceive pain. Although contemporary models of pain acknowledge that pain is not a direct readout of nociceptive input, the neuronal processes underlying cognitive modulation are not yet fully understood” [Wiech]. Fortunately, a full understanding of the details of the neuronal processes is not needed for recovery from the problem!
Recovery is possible because the brain has a wonderful ability to heal through neuroplasticity. The brain creates the experience of pain to try to help us. If it becomes convinced, at a deep level, that it no longer needs to protect us and if we provide useful therapy such as learning, activity, biofeedback, guided imagery and meditation, then the brain can heal itself. The stronger our belief that a therapy will help us, the better it will work. This is most dramatic in studies of the placebo effect, which is very strong for chronic pain and has been investigated by Tor Wager’s group in some detail. In their 2004 Science article they reported: “In two functional magnetic resonance imaging (fMRI) experiments, we found that placebo analgesia was related to decreased brain activity in pain-sensitive brain regions, including the thalamus, insula, and anterior cingulate cortex… a major portion of the placebo effect may be mediated centrally by changes in specific pain regions. This account acknowledges that pain is a psychologically constructed experience that includes cognitive evaluation of the potential for harm and affect as well as sensory components”. So here again we have hard science showing that chronic pain is a brain problem in addition to whatever body problem may exist [Rainville]
Unfortunately, pain transitions smoothly from being only a body problem associated with damage to body tissue (nociceptive pain) to being also a brain problem (a cerebral process) if it persists for months or years. Despite the breakthrough research using fMRI in a laboratory setting, there are presently no practical devices to measure either the body problem or the brain problem. Therefore this transition is invisible not only to patients, but also to medical professionals. Every chronic pain sufferer that I have met is firmly convinced that their pain is a body problem. After all, it started as a body problem and, years later, the pain is still felt in the body where it started, eg. the lower back. So it is natural to assume that the problem, like the pain, is the same. It is only after this misconception has been corrected that the chronic pain sufferers have been able to use brain-based therapies and recover.
An additional problem is that physicians, who are educated and skilled in dealing with body problems, are not educated and skilled in dealing with brain problems. Sometimes, even if the physician knows enough about chronic pain to know that dealing with the body is not the answer for a particular patient and advises the patient to try a brain based approach from a psychologist or psychiatrist, the patient insists on one more surgery or other body-based therapy! Thus many chronic pain patients continue to receive body-based therapies instead of the brain-based therapies that they need to recover. Curing a brain problem with a body-based therapy can only work indirectly through the placebo effect, which is strongest for surgery, then injections, and then prescription drugs with strong side effects. Fortunately there are clinically- tested methods to work directly on the brain problem.
The problem of chronic pain is of such enormous personal, social and societal importance that pioneers have already developed useful methods for dealing with the brain problem, even without the aid of a detailed understanding based on hard science that we can hope for in the future. One example is in the next section. More have been collected in the section near the end of this document titled: “Four Useful Methods and the Science Behind Them”. These methods have not only helped thousands of people overcome chronic pain, but can help guide the development of deep fundamental understanding of the cerebral processes that create chronic pain. Hopefully this fundamental understanding will help in developing even more effective, individually-tailored, methods for overcoming chronic pain.