When we talk about pain, we usually focus on the physical area of the body where it hurts. We use metaphors to say it is “stabbing” or similes to talk about pain feeling like a “vice grip.” But what if pain really was all in your head? It turns out that technically that is 100% accurate. The brain is the mechanism that processes all sensation in the body. When a muscle is sore, it’s sore because nerves send a signal that your brain processes as pain.
But a brain in pain does even more than that: it remembers it and responds differently to words and situations the longer it is processing pain.
Thomas Nevian and his colleague Mirko Santello from the department of physiology at the University of Bern have found a mechanism in the brain of laboratory mice that actually remembers pain and contributes to it becoming chronic. When laboratory mice experienced long-term (chronic) pain, the neurons in a brain region called Gyrus Cinguli changed so that traces of that memory became “etched” in those neurons. Once changed, the researchers found that this brain memory (a “memory trace”) is irreversible.
Nevian and Santello found that the Gyrus Cinguli was more receptive to electrical impulses signaling pain in the brain due to a specific ion channel that was not well-regulated. This ion channel basically determines the electrical conductivity in the cell membrane. Think of the cell membrane as a fortified wall keeping the enemy (an electrical pain impulse) at bay. If there is a hole in the wall (a down ion channel), then the enemy (pain) not only streams through that hole but also remembers where it is.
The researchers then tried to figure out a way to boost the activity of that ion channel – to plug the hole in the cell membrane that allowed electrical pain impulses to stream through unimpeded. They found that the neuromodulator serotonin (the “feel good” hormone in the brain) reduced pain in the lab mice. This offers strong support for the use of serotonin-boosting anti-depressants and also gives some insight into how they work to fight chronic pain. Although this is promising research, both scientists caution that new treatments may be a long way off: “
Finding a way to fortify the brain’s pain-sensing cell membrane is crucial, as the brain begins to process chronic pain differently over time.
Researchers at Technische Universitaet Muenchen (TUM) found that as pain moves from an acute event to a chronic one, the way the brain processes it becomes more emotional. Professor Markus Ploner, Heisenberg Professor for human pain research at the TUM School of Medicine, and his team took electroencephalograms (EEGs) of volunteers who were asked to rate their pain on a scale over time as they experienced a heat stimuli to the hand. Ploner was shocked by the results:
“We were absolutely amazed by the results: After just a few minutes, the subjective perception of pain changed — for example, the subjects felt changes in pain when the objective stimulus remained unchanged. The sensation of pain became detached from the objective stimulus after just a few minutes.”
In other words, although the pain remained the same, the brain exhibited an emotional response to it as time passed.
Not only did the brain begin to interpret pain as time went on, but it also began to anticipate it, affecting perception of it. Ploner and his colleagues applied a painful laser to the back of study participants’ hands, asking participants to rate the sensation. They then applied two creams to the back of the hand. Participants were told that one had a pain-relieving substance while the other did not (neither had a pain reliever). Again, Markus Ploner:
“The subjects assessed the pain on the skin area with the allegedly pain-relieving cream as significantly lower than on the other area of skin… Our results show how differently our brain processes the same pain stimuli. Systematically mapping and better understanding this complex neurological phenomenon of ‘pain’ in the brain is a big challenge, but is absolutely essential for improving therapeutic options for pain patients.”
This perception and the way the brain can manipulate the sensations of pain filters into everyday life, even as something as small as reading the newspaper.
Samantha Fashler, a PhD candidate in the faculty of health at York University used eye-tracking software to find that those experiencing chronic pain were more focused on pain-related words (e.g., ache, distress, and agony) for longer than those who were not suffering from chronic pain. While this may not seem like an important breakthrough, it speaks directly to whether or not the way the brain perceives and attends to pain has anything to do with its intensity and duration. Says Joel Katz, Canada research chair in health psychology and the co-author of the study:
“We now know that people with and without chronic pain differ in terms of how, where and when they attend to pain-related words. This is a first step in identifying whether the attentional bias is involved in making pain more intense or more salient to the person in pain.”
Just because pain is in a person’s head doesn’t invalidate their experience, but it does tell us more about how we can treat it. Have you experienced these effects in your own life?
Image by Day Donaldson via Flickr