How can you define pleasure and pain

An unpleasant sensory experience - what is pain?

A lot can be said about pain. Also a lot of things that are a nuisance for chronic pain patients. Then there is the talk of: “Let pain be your teacher!” Or “Pain shows you your limits” - unfortunately these are only poetry albums, it has little to do with the reality of people who suffer from pain.

Since I suffer from a chronic headache, it was for me to know why we are in pain and what is going on in our body.

What is pain and what is it good for?

I found an initial answer to the question of what pain is in the International Association for the Study of Pain. After years of discussion, the following definition was agreed there in 1993: "Pain is an unpleasant sensory or emotional experience that is associated with actual or potential tissue damage or is described by affected persons as if such tissue damage were the cause."

I knew the senses from school, biology class, middle school. You learn how to hear, see, smell, feel and taste. We need all of these senses to orient ourselves in the world. Sometimes they give you pleasure because something tastes good, sometimes you shiver because it has gotten cold. I can still remember how the cornea, lens, retina, nerve form the apparatus with which we see the world. I could even draw the sticks and cones, those receptors that collect the light. In comparison, pain is an ugly duckling - nobody talks about it, nobody likes it. It marks an important limit: If something is too sharp, we feel pain, if it is too cold and our toes threaten to fall off, we feel great pain. Whenever something threatens us, pain kicks in.

Pain as a stimulus

But because nobody really likes to deal with pain, most of us think about it as we did almost 400 years ago. René Descartes ’idea of ​​pain has gotten stuck in our heads at least as much as his“ I think, therefore I am ”. In 1662 he wrote in the "Essay on Humans" that pain as a stimulus was conducted into the brain via nerve tracts, as if one were pulling the rope of a bell. With the means at the time, that was observed correctly. We cut our fingers with the knife, then the brain rings and we feel a sharp pain. The brain gives the order: pull your finger away, hold it up, stop the bleeding.

Descartes couldn't explain much, but it was a start. Biologists, natural philosophers, physiologists and doctors stuck to this idea for a long time. It was assumed that there are specific nerves for pain perception that end in a certain place in the brain - that is, in a center for pain. This theory was refined by the German-Austrian physiologist Max von Frey at the end of the 19th century. He called it “specificity theory” and examined skin points that seemed to be responsible for pain.

Even a layperson can imagine that this theory did not lead very far. Why are some temperatures comfortable and others terribly painful? If the water in the shower becomes too hot, we automatically jump out of the danger zone. Why do we react to such different stimuli as warmth, cold, sharpness, pressure with pain? If these influences are only conducted to the brain via specific nerve tracts, then there would have to be some entity there that evaluates and connects this information. Somehow it seems too complicated, because when it comes to pain, the brain has to go fast too.

Type and intensity of stimulus

That is why a Berlin doctor with a Kaiser Wilhelm beard, Alfred Goldscheider, began researching the stimulation of nerve cells. His main idea founded the second school of pain theories: It is not the receptors that are different, but whether we feel pain depends on the type and intensity of the stimulus.

Today we know all this more precisely: Nerve endings - so-called nociceptors - are responsible for the sensation of pain. They react to pressure, heat, cold, injuries. When a certain threshold is exceeded, they become active and warn us of tissue damage. 80% of all nerve fibers outside the brain and spinal cord are part of the pain perception system. So it makes sense to ask why we don't feel pain all the time with such a pronounced and comprehensive system. One reason is that around a third of nociceptors only become active when their colleagues have already released enough messenger substances, which happens, for example, in the event of an inflammation or a burn. Nociceptors in turn produce neuropeptides that are important for the pain mechanism. The best known are the endorphins. The mysterious among them is called Substance P. Substance P sounds as if you didn't want to bother with the name. Initially, the P stood for powder, it is now the abbreviation for English pain (Pain). Substance P causes the blood vessels to widen (reddening) and sensitizes the nerve cells in the spinal cord. Then a cycle is set in motion that finally informs our brain via the spinal cord and becomes conscious there as pain.

Theory about pain

I didn't expect pain to be a downright theoretical problem, with unresolved contradictions, vague guesses, and plenty of questions. And that a really solid scientific explanation is not yet 50 years old. But in order to understand what pain is, I find it important to know how it has been thought and researched over the centuries. After all, we are all glad that today we no longer regard pain as a punishment from God or the result of mixed up body fluids.

Nevertheless, what I am about to report is only a theory, albeit a very convincing one, which has been around for a long time and still has the greatest influence today: the gate control theory, developed more than 50 years ago by the Psychologist Ronald Melzack (right on the picture) and the neurophysiologist Patrick Wall (left).

I find it nice when researchers first take a step backwards. Melzack and Wall did the same thing, choosing as a starting point a few fundamental problems that kept cropping up in connection with pain and which up until then could not be explained. (The story is retold in English in this video.)

Your theory should be better, assuming that the relationship between pain and injury is highly variable. A clear example of this is always the soldier who has a severe gunshot wound but only feels the pain after he has brought himself and his comrades to safety. But Melzack and Wall also asked themselves how it happens, conversely, that a completely harmless stimulus causes hellish pain or that pain can persist after the injury has healed.

How can you explain that the location of the pain is sometimes not identical to the location of the injury or that the type and location of the pain change over time? From the beginning they knew that they could only answer these questions if they assumed that pain had a physiological and a psychological dimension.

So, they got up and followed the injury from the external wound into the depths of the body. They shifted their research from the periphery to the central nervous system and showed that information is constantly being filtered, changed and selected there.

A gate filters the pain information

The last piece of the puzzle for their theory provided the two in 1965 in an article entitled: "Pain Mechanisms: A new theory". They had discovered a gate. At one point on the spinal cord - the posterior horn - two nerve fibers meet: Adelta and C fibers. While the C-fibers conduct the pain stimulus further to the brain, the thicker Adelta fibers can prevent this. So some open a gate, others close it again: the gate control theory was born.

The rear horn acts as a kind of signal box. The messenger substance glutamate transfers the excitation of the peripheral nerve fibers to the spinal cord. Nothing seems to be stipulated here, everything acts depending on the situation and condition. A given stimulus, such as For example, a touch that we normally interpret as pleasant can, in certain cases, trigger an intense sensation of pain.

If everything is normal, then in the dorsal horn it is easy to distinguish between pain and simple stroking; However, should we find ourselves in an extreme situation, for example in a car accident, the system can also ensure that we do not feel anything at first.

And unfortunately it works the other way around: If the system is particularly active, even the smallest injuries are perceived as painful. In the case of chronic or neuropathic pain, there is such a change that the entire system has collapsed.

People with migraines also know only too well what it means when light, noise and all other sensory perceptions suddenly only cause pain.

The brain decides whether we feel pain

Gate control does not only take place in the spinal cord, as Ronald Melzack and Patrick Wall initially suspected. The stimuli are also processed further up, in the diencephalon area and in the cerebral cortex, before we can even register them as pain. Here, too, messenger substances work to block this stimulus. Only when a critical value is exceeded do other areas in the brain switch on and we feel pain.

If the pain stimulus makes it into the brain, several regions are responsible for processing it. In the cerebral cortex, sensory impressions such as heat, cold, touch are processed, in the limbic system the stimulus is evaluated on the emotional level (pleasant, threatening, stimulating, etc.), and in the prefrontal cortex, where we store memory contents, the stimulus and its emotional level Finally linked to assessment. Only then do we have pain.

Another section of the frontal lobe finally decides how to deal with the pain, and this is where the body's own pain relievers such as endorphins are produced.

Fight the pain in the right place

Adelta, pain matrix, endorphins, limbic system - sounds great, but wicked tongues claim that all of the research has done little for pain patients. But somewhere along the path of the stimuli through the body lies the key or several keys to relieving or stopping pain. In all these places one can build up obstacles and thereby override the pain system.

And with all things that we discuss here in the blog and at M-sense, with triggers, painkillers or other therapies, we always intervene in exactly this system that Melzack and Wall developed.