The brain is a miraculous organ. It governs everything our body feels and experiences, regulates body functions both automatic and voluntary, and does so with marvelous efficiency.
Every day, research is gaining new understandings about how the brain works the way it does and why it functions in certain ways.
One area of study that is particularly fascinating for both its depth and breadth is how the brain processes pain. On a basic level, nerves in the body feel a stimulus and send that signal to the brain through neurotransmitters. The brain then interprets the signal as pain (or hot, cold, etc.) and then we experience the feeling. This all happens at speeds between two and 200 miles per hour.
But now researchers are finding that the brain processes chronic pain in different, more subtle ways. Researchers at Technische Universitaet Muenchen found that even after pain persists for a few minutes (as in a serious broken ankle rather than just a pricked finger), the brain begins to process the pain in its more emotional centers.
Professor Markus Ploner, Heisenberg professor for human pain research at the TUM School of Medicine, and his team wanted to know what happened in the brain when pain persisted. They applied a painful heat stimulus to the hands of 41 study participants over a period of time, asking them to continuously assess their pain with a slider that indicated the level of intensity.
Consistently, even when the stimulus remained the same, participants rated the intensity of pain as increasing. Looking at EEGs over the course of the experiment, Ploner and his team watched as the area of pain perception moved from the sensory area of the brain to the more emotional areas, indicating that the brain was no longer processing physically. Researchers noticed an interesting change in the brain. Says Markus Ploner:
“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 another experiment, researchers found that the anticipation of pain also increased the perception of it. Twenty study participants had a painful laser applied to the back of their hands and then were asked to assess their level of pain. A short while later, the same laser was applied, but this time, a cream was applied to the hand prior. Study participants were told that there was a pain-relieving property to the cream (it was, in fact, a placebo). Those with the placebo applied to their hand rated their pain at much lower levels than before.
More than just increasing pain by the anticipation of it, researchers at the University of Bern have found that neurons may actually remember chronic pain.
Thomas Nevian from the department of physiology at the University of Bern and fellow researcher Mirko Santello discovered a cellular mechanism in the brains of mice that contributed to chronic pain. A region in the brain that regulates emotional response to pain, the Gyrus Cinguli, may help the brain develop what they call the “pain memory.” They found that cells in this region, stimulated frequently by pain signals and lacking a specific membrane in the cell that measures its electrical properties, eventually developed more nerves, which in turn “remembered” former pain.
Nevia noted that:
“The neurons are constantly activated by a noxious stimulus, thus building a memory trace for pain that becomes irreversible. Our idea was to understand this mechanism better to derive potential new treatment strategies.”
Their next step was attempt to regulate this ion channel with electrical irregularities by activating a specific sensor with the neuromodulator serotonin. Serotonin appears to dampen the perception of pain in the particular sensors that have built up a pain memory, which can lead to real relief. This may be one of the first studies to begin to understand exactly how tricyclic antidepressants work to help control chronic pain.
Although serotonin’s effectiveness has already been proven in existing research, what is new is the receptor targeted, which may lead to a novel class of medications for chronic pain treatments. The researchers were quick to point out that the implications are important but the view must be long-term:
“…we were able to identify a specific subtype of serotonin receptor that reduced the perception of pain more efficiently. This is an important result, which might help to treat chronic pain more efficiently in the future… even though we made an important step forward now, it will take some time before novel drugs will be designed based on our results.”
Perception is one factor that can exacerbate the sensation of pain, but can words also hurt?
Researchers at York University found that chronic pain patients were more drawn to pain words than those who were pain-free. Using eye-tracking software, they recorded reaction time and eye movements for 51 chronic pain patients and 62 pain-free study volunteers. They found that chronic pain patients found and lingered on pain words such as “ache” faster and longer than those not experiencing pain.
In thinking about how the brain processes pain, this is important research in that it can help to understand whether or not specific language can help or hurt pain treatments. There are larger implications when it comes to treatment options, as clinicians, counselors, and doctors may need to think about the words they use with their patients. Says Professor Joel Katz, Canada research chair in health psychology, 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.”
This research only begins to scratch the surface of our understanding of how the brain processes pain. The most encouraging parts of the findings are those that indicate the incredible neuroplasticity of the brain. This means that the brain is constantly evolving and changing, which means that there is real potential for the brain to help heal and treat the causes of chronic pain.
For more on the miraculous potential of the brain, take a look at NOVA’s PBS program “How Does The Brain Work?”
Image by Allan Ajifo via Flickr