Pain is an Output

There was an interesting study that came out in June of this year that got a bit of press and activity on social media that our research group at ISPI had a bit of banter through some emails that I thought I would share in this post as a summary of our discussion. As Adriaan stated when he started the email chain: “…I like this paper and will use it to underscore: PAIN IS AN OUTPUT…”

Nociception is not pain.

Let me go into a bit of detail about the study for some backdrop. In the study they looked at two people who have a genetic disorder that does not allow them to experience pain. These are the individuals that can put their hand on a hot stove and report that their hand will feel warmer, but that it is not painful. They had each of these individuals receive a ‘pinprick’ stimulus. (Something that most of us would say “ouch that hurts” when applied.) During the stimulus they performed a fMRI to evaluate what brain activity was going on during the stimulus and also did the same stimulus with a few age-matched normal controls. (One can question how normal they are if they submit to research where we are going to receive a ‘pinprick’ stimulus, but that is a separate post for a later time.) What they found was that the key areas for the “pain matrix” would ‘light-up’ on fMRI for both groups in the same fashion. The difference was that the normal control group said it was painful, but the other two people that don't experience pain did not. So when you give a noxious/attention grabbing stimulus there are key areas of the brain that were activated in both groups. Pain is about the output, not the input. Nociceptive input activating the ‘pain matrix’ does not mean it is pain. Pain occurs only when it becomes an output, the person says and behaves in an outward way that they have a pain experience. Nociception is not pain.

We have known for many years based on multiple studies there are key areas of the brain (the ‘pain’ matrix) that are activated during a pain experience. The problem with terminology is that by calling it the ‘pain’ matrix, we have allowed one of the largest errors in science interpretation (correlation does not imply causation) to creep into some peoples thinking. Just because these areas of the brain correlate to a pain experience, it does not mean that they cause a pain experience. That is exactly what this study verified. These individuals with the inability to feel pain could have their brain light-up in the similar fashion as someone experiencing pain and yet not have pain. Thus once again confirming pain is an output, not an input. Both people had the same input from the stimulus all the way to the brain activity, yet one group had the output of pain and the other did not. Pain is an experience and cannot be “found” with an fMRI study any more than we can scan someone’s brain to find out if they love something.

It would be like looking at a map of the US and being able to see which cities are more active than the other cities.

Side note of caution with fMRI study reports: I want to highlight a bit of caution anytime you read a fMRI study. While they are very interesting and involve amazing technology that has led to many discoveries of how the brain works, they do have significant limitations also. First we need to realize that looking at a fMRI brain scan only tells us there is increased blood activity in that area of the brain. What that increased activity is exactly is not always known, because the neurons taking up that increased blood flow can be facilitatory and/or inhibitory in action. Also realize the detail we can image is very gross at this time. It would be like looking at a map of the US and being able to see which cities are more active than the other cities. We are nowhere near looking at the street, or individual neuron level, yet. So knowing that you see one city is more active makes it hard to determine exactly everything that is going on. If you saw that New York was more active then Chicago, it only gives some of the picture. Because what is happening at Broadway and 5th Avenue is usually different than Times Square. Then to get even into more detail is that we have no idea on what sort of temporal firing pattern is happening and with what neurotransmitters between each synapse.

I think on some levels life would be easier for clinicians if we could find pain on a scan. No more wondering if a person is faking their pain or wondering how much pain they are really in. We could apply a treatment and see if it reduced the image on the scan and verify its effectiveness. We could then treat pain in a black and white biomedical fashion and not have to get into the multi-color challenging biopsychosocial aspects of care. But pain is about someone’s current experience which takes into account sensory and affective dimensions and includes past experiences and beliefs.

Louie pointed to the fMRI study he and Adriaan published. In the study they took an individual with chronic back pain and provided pain neuroscience education. Why did her brain scan look different after the education? We think it's because they got her to modulate the input (nociception). It was different the second time because of the organization/ motor control of the activity which was modulated by her improved understanding of pain, i.e. it was less of a threat.

I think Mark summed it up nicely in one of his emails: “Just more examples of us trying to reduce an extremely individual and unique experience to a red blob on a fMRI screen. Maybe medicine one day will decide they can put down the complicated evaluative tools and simply listen and communicate empathetically to understand a pain experience. There is a lot of life experiences that goes into the red blobs displayed on fMRI.”

What say you?

Special thanks to my ISPI research colleagues for providing a lot of the content of this post through our email banter. (Adriaan Louw, Louie Puentedura, Steve Schmidt, Ina Diener, and Mark Kargela)

Via Dr. Kory Zimney, DPT

Interested in live cases where I apply this approach and integrate it with pain science, manual therapy, repeated motions, IASTM, with emphasis on patient education? Check out Modern Manual Therapy!

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