How we feel pain

The more that we understand about pain, the better chance we have of doing something that will truly influence it. And the most important thing to understand is that, no matter what kind of injury or disease we may have, pain is an output of the brain.

We may have a serious injury that hurts - a deep wound for example. It may seem obvious that this wound is the cause of our pain. And yet this is not entirely the case. A surprisingly high number of people attend accident and emergency departments every day with serious injuries just like this who are not, at the present moment, experiencing any pain.

When we are injured, messages from the body will shoot up to the brain to tell it that something is wrong. The brain then starts to gather information so that it can work out what might be going on and what response is needed. This information comes from many sources, including the incoming signals from the body, memories of past experience, and aspects of the current context that might tell us about the relative safety or danger of our situation. All of this processing happens automatically and outside of our awareness, so it is not something we can consciously influence. Taking all available information into account, the brain then builds a picture of the most likely scenario that accounts for the information it has. The brain will also form an opinion about how we need to respond. The outcome of this processing may be that we need pain. The purpose behind this may be to alert us to an injury that needs attention, to make us stop something that could harm us or to warn us that we have been overdoing it.

Pain always comes from the brain. There is always a purpose to it, which is usually to protect us in some way. And the very fact that we are experiencing pain means that mental processing has already taken place. Quite simply, pain cannot exist other than as a result of processing by the brain. So although pain feels like a very direct and immediate experience, it is not. We can never experience pain that has not already been processed by the brain.

It can be hard to understand that something that feels so direct and 'real' is so strongly influenced by the automatic mental processing that has taken place before we were even aware of what we felt. This has led to some people mistakenly thinking that some pain is 'real', and that another, different kind of pain is 'in the head'. But this is not accurate. The mental processing applies to all pain, including pain that we find easy to understand (eg where there is visible injury) as well as pain with no obvious physical cause.

We can use visual illusions to experience and understand the role of automatic mental processing. Look, for example, at the picture below.

colour constancy block.jpg

We look at this picture, and it quite clearly seems to us that we are looking at two sides of a cube, one of which is light and the other dark in colour. In fact, we see it like this because our brain has processed the image and come up with the best possible explanation for the patterns and colours it sees. In other words, we 'see' what the brain has decided we should see on the basis of processing that has taken place.

When we cover the middle of the picture and look again, we can quite clearly see that both squares are mostlly the same colour. But we see them as different because, having taken into account all of the additional information presented, the brain creates for us a very particular picture.

This processing is so powerful that even when we 'know' that the squares are the same colour this does not change what we 'see' when we look again at the picture. Our brains take more notice of other factors, such as our past experience of what objects look like and the colours of the background when building up the image that we see.

It is also important to notice that it doesn't seem to take any time for this processing to take place. We look at the picture and immediately 'see' the illusion. Our minds work very quickly to create the picture in front of us. While we can tell from the visual illusion that mental processing must have taken place for us to see it as we do, we are neither aware of this or of any 'working out' time. It feels like we are just directly seeing a picture as it is.

This gives an important insight into the way that our brains also work when we experience pain. The process is the same as with vision. The brain receives information through the senses and combines it with previously stored knowledge and background information. It then comes up with the most likely scenario and creates the experience for us.

It is an incredibly helpful, accurate and fast system which usually protects us and serves us well. But it is not infallible. It sometimes causes us to feel intense pain which is not adaptive or helpful. The mind basically takes into account all of the information it has and comes up with the most likely, best possible story to explain it all. Just occasionally, the mind gets it wrong. Just like the mind sometimes gets visual illusions wrong, causing us to 'see' something which we know not to be accurate.

Is pain real? Yes, it is real. If we experience pain, then it is real pain. Is the picture in this article real? Yes, it is. We really see two differently shaded squares. Both experiences are real. But neither represents the truth of the situation. The image we see is of different shades, but we can know that the truth of it is that they are the same. Likewise, it is possible to experience very intense pain even when there is no serious injury or disease behind it. We can know that the pain we experience is real, but it still may not accurately reflect what is going on in the body.

What if we need to feel less pain? Is there anything that would help? The short answer is that there can be. In fact, in the course of every day there are usually some moments when persistent pain is less intense, and other moments when it is far more intense. So we can already know that even persistent pain can change to some extent.

Because the brain is continually processing messages that it receives, and linking these messages with other information from memory and current context, it is subtly changing the intensity of our pain on a frequent basis. It is this process that we need to be able to influence if we want to change pain on a long-term basis. In order to be able to change our experience of pain, we need to be able to influence the conditions that the brain is taking into account when it is working it all out. If we change enough of these, then we will change our experience of pain - just like we can change our experience of what we see by changing the visual information around the cubes in the picture.

#pain #persistentpain

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