Pain Part 1: Enter the Matrix

Perhaps you remember seeing the popular movie “The Matrix,” and maybe you are wondering what on earth it has to do with pain physiology. The movie presented a complex alternate reality, which is not entirely different from the complexities of pain science that have been revealed in the last few decades. In fact, neuroscientists have spent years trying to identify the “pain center” in the brain, only to conclude that there is no singular pain center. Instead, neuroscience has discovered a whole network of pain processing centers collectively referred to as the pain matrix. To appreciate the pain matrix, let’s flashback to simpler times.

Cartoon of external demons acting to cause pain

More than 350 years ago, Rene Descartes presented a theory that shaped the way we understood pain for centuries. At the time, the widespread belief was that pain stemmed from outside of the body, existing as a kind of divine test—something that could only be addressed through spiritual means. Demons were exorcised with elaborate rituals in hopes of relieving people of their physical symptoms.
Descartes suggested that pain originated from within the body, starting from the injured area and moving to the brain. For a long time, this general concept of pain prevailed. However, current research has improved our understanding of pain and effectively debunked the longstanding Cartesian model. With the development of functional brain imaging, we now understand that 100% of pain is created by the brain.

Imagine you step in a pothole and sprain your ankle. Your nervous system begins sending messages (nociception) from your ankle to your brain. These messages aren’t pain itself, but rather signals telling your brain that your body has encountered potential danger. Once your brain receives these nociceptive signals, the pain matrix can decide what to do with the warning of danger. It might cause your ankle to hurt– or not. Your brain is designed to keep you safe, so it depends on the context. If you sprain your ankle crossing the street while a bus is speeding toward you, it’s likely you won’t feel pain as you run to get out of the way. To ensure your safety, your brain won’t slow you down by creating a pain experience until the even bigger danger of the speeding bus is no longer a threat. Only then will you notice the pain that draws your attention to your ankle.

Pain is your brain’s way of getting you to take appropriate action. In this case, that might mean getting a ride home and elevating your ankle. You’ll go through the inflammatory stage for a few days (redness, warmth, swelling, pain and loss of function,) which should cue you to take it easy as the healing process begins. The repair stage of healing takes 4- 6 weeks to mend injured tissue, during which the symptoms of inflammation should clear up. As you gradually load your newly repaired ligament, the remodeling stage will continue for up to 6 months to fortify the area so it can withstand the stressors of your habitual movements. By the time you’ve moved on to remodeling, inflammation and pain should be a distant memory. But what if it isn’t?

I’ve seen patients whose ankles hurt years after the original sprain– what is that about?!? Of course, there are cases where people re-injure themselves and perpetuate an injury, but there are also many cases where no tissue damage remains (no signs of inflammation and medical imaging is negative for pathology) and yet pain persists. An extreme example of this is phantom limb pain. Amputees experience pain in a limb that is no longer there– a phenomenon that inspired researchers to question Descartes’ theory about pain in the first place. Clearly, in these cases pain isn’t coming from the injured tissues!

Researchers have consistently found that remarkable changes occur in the nervous system of a person who experiences pain for more than 3 months. When the brain senses ongoing danger, it adapts by making the nervous system even better at sending warning messages and amplifying the pain experience with the hope that you will eliminate the danger if the pain gets louder and more unbearable.

The trouble here is that the brain isn’t always accurate in its assessment of danger. Once the pain matrix is on high alert, the nervous system can interpret all kinds of things as potential danger: stress, allergies, an ache in another part of the body, gastrointestinal upset, memories of previous trauma, anxiety—even things as innocuous as temperature, pressure, or weather-related changes—may be interpreted as a threat requiring further escalation of the pain experience.

Fortunately, the brain and the nervous system are both incredibly adaptive. By increasing support and safety and decreasing potential danger, the same processes that occurred to upregulate the pain matrix will begin to reverse themselves. Given the right conditions, the nervous system can adapt within a few minutes to de-escalate the pain experience.

So what does this mean for treatment of chronic pain? Simply put, the most effective treatments won’t just target the body. They will also work with the thoughts, feelings, and fears of the pain generator itself– the brain.

A number of strategies are effective in treating the brains and bodies of people in chronic pain:

People with chronic pain need to be treated like people. This should go without saying, but unfortunately, they are sometimes treated like problems by their healthcare providers. If this has happened to you, it’s time to move on. You deserve better.
Beyond basic kindness and humanity, find a therapist/provider that you actually want to spend time with. Establishing a sense of rapport does actually improve results, in addition to improving the quality of your healing experience.
Your voice matters. Your perceptions are critical to your wellness, and your healthcare team should be interested in more than your physical symptoms. Don’t be surprised if you are challenged to see things from a new point of view, or asked to take note of any patterns to your symptoms (i.e. pain log,) but overall, you should feel heard.
Set realistic goals. A common mistake is striving to never have pain. Pain is part of being human. Acceptance of this fact of life can help you to adapt your goals so that they are attainable! If you aren’t sure if your expectations are realistic, ask your therapist.
Keep moving! If you stop doing healthy self-care behaviors and things you enjoy, the brain may very well intensify the “danger!” signals. Work with your team to find movements that do not increase your pain significantly, and give your brain some endogenous opioids (translation: natural pain-relievers released when we exercise regularly.)
Fill your life with as many enjoyable things as possible, and learn to find joy in the simple things. You may find yourself avoiding activities due to pain, but eliminating the things you love further triggers the pain matrix… and gives you more time to dwell on the pain, or even identify with it. You are more than a list of diagnoses or symptoms, so make sure your brain knows it by keeping your life full of positive and neutral experiences to balance out the painful ones.
It takes a village. Plan on growing your support team to include not only medical professionals, but anyone who helps you feel safe, heard, relaxed, and at ease. Limit your time with people or situations that increase your stress.
Don’t let anyone tell you it’s “all in your head.” This phrase is actually true, considering all pain is an output of the brain, but that doesn’t mean that your pain isn’t real. Your (very real) pain is likely triggered by many factors, including biomechanics, emotions, thoughts, hormones, etc. Pain is complicated!
Get curious. Turns out just learning about pain can quiet the pain matrix, so you’ve already taken a step towards resilience just by reading this blog!

Stay tuned for resources to help you use pain science to treat chronic pain in my upcoming blog, Pain Part 2: Befriending Pain.