Signals from everywhere in the body, coalesce in specifics area in the brain where it’s then interpreted and either ignored or acted upon. When it comes to pain – smell, taste, temperature, touch, or pleasure can have an impact because they all end up in a similar location via similar neuronal pathways. By increasing the input from these other sources, the brain can be tricked into diminishing the pain.
Our nervous system has two parts. The central nervous system is made up by the brain and spinal cord. This is the main hub. They get data from both the sensory and motor systems (the peripheral nervous system) which collectively acquires data from the entire body. In this way we send sensory information on what’s happening in our environment through the spinal cord to the brain. Once processed, the brain then sends whatever action is needed back to the proper sites via motor nerves.
You touched a hot stove? This is instantaneously transmitted up the chain of command where the brain then shoots a demand to the motor nerves in the hand- move it or lose it! Special pain receptors called nociceptors are activated when they feel a change in their environment from slight pressure, to heat, to tissue damage. Different nerve fibers react to different issues e.g. a laceration vs. a fracture vs. a sore throat. Each causes a chemical reaction which determines how it’s sent through the spinal cord and ultimately interpreted in the brain. Some reactions are reflexive, as with the hot stove to instantly protect us, otherwise pain in general is far more complex. It gets evaluated, analyzed, catalogued and even associated with emotions.
Mood, past experiences and expectations can all change how it’s interpreted. Did you touch the stove after a fight with your spouse? Or the days you got a raise? What we associate with that moment may change how it’s seen the next time. If you stepped on a rock and it wasn’t an issue or it caused a laceration and infection will define how you view rocks in the future.
Now new research has found simple changes in how we position one body part in relation to another can also change pain perception. It’s built on “the thermal grill illusion” that helped us to understand how pain is sensed in the brain. In that study they applied warm – cold- warm temperatures to the index, middle and ring fingers and surprisingly found it caused a paradoxical, and sometimes painful sensation of burning heat in the middle digit, even though it was bathed in cold. Using precisely controlled stimuli in order to activate specific pain patterns in the brain, they were able to show a three-way interaction between hot, cold and pain signals and how the order mattered. Heat applied to the two outside fingers actually blocked brain activity normally driven by the cold temperature applied to the middle one.
Cold usually inhibits pain. But the benefit was prevented when it was surrounded by two heat sources. In this case the feeling of pain was actually increased. To make the response even more intriguing they then learned it was affected by how the fingers were spatially arranged. When the middle finger was crossed over the index the paradoxical level of heat was reduced. If the index was cooled and the other two heated and then the middle as crossed over the index, heat sensations were increased. Simple changes in how the body was positioned had profound effects on neural pathways and how the brain perceived pain!
Focusing on how confusing the brain can impact chronic pain, another study showed that putting our hands on “the wrong side” also disrupted sensory pain inputs. Participants were given a 4-millisecond laser generated pin prick of pain. They then ranked the pain sensation while their brain waves were tracked via an EEG (electroencephalogram). In all instances the perception of pain as well as brain wave responses were lessened when their arms were crossed over to the other side.
Because we usually touch, pick up and use items on our left side predominantly with our left hand and those on the right side of our body with our right hand, the brain sets up internal maps that define our external space this way. Right hand with right space and left hand with left space. This leads to a precise and effective means of processing sensory stimuli. But when we cross our arms these “maps” are mismatched and can’t be activated which weakens the brain’s ability to process incoming stimuli, including pain. Next time you get hurt don’t just apply pressure and ice, cross the appendage to the opposite side as well.
A chance encounter with a new technology called “Mirage” helped arthritic fingers feel less pain. During an open house at the University of Nottingham’s psychology department, children enjoyed placing their hand in a box containing a camera which then showed the image on a screen. That image then showed the illusion that one of their fingers was being stretched and shrunk by someone gently pulling and pushing from the other side of the box. When a grandparent asked to join the fun the result was astonishing – her arthritic joint felt better. They later tested a small sample and found it halved the pain in 85% of cases. One participant said, “It was a very weird sensation, but as my finger was supposedly being ‘stretched’ it felt more and more comfortable. I just wanted it to stay like that, to keep that image in my head. “
The illusion worked for some with stretching or shrinking and with others both events, but only when the actual painful parts of the hand were manipulated.
Learning more about why applying additional stimuli, altering spatial patterns or changing how the brain sees a painful joint could open exciting new possibilities for managing chronic pain.
-https https://pubmed.ncbi.nlm.nih.gov/21440992/
-Https://www.sciencedaily.com/releases/2015/03/150326130837.htm
-https://linkinghub.elsevier.com/retrieve/pii/S0095454312000553
-https://www.ucl.ac.uk/news/2011/may/crossing-your-arms-relieves-pain
-https://www.hindawi.com/journals/np/2017/9724371/
-https://www.bbc.com/news/health-13452457
-https://www.bbc.com/news/health-13068924