When a person presses on the temples or the back of the head to soothe a feeling of pain in the head or rubs the elbow after unexpectedly bumping into a hard object, it often brings some relief.
According to Neuroscience News, it is believed that pain-responsive cells in the brain calm down when neurons are patted.
A team of scientists at MIT’s McGovern Institute for Brain Research first observed the phenomenon in the brains of mice.
The relationship between touch and pain
The researchers presented the results of their discovery, which was published in the journal Science Advances, which offers a deeper understanding of the complex relationship between pain and touch and could offer some insights into chronic pain in humans.
Fan Wang, a researcher at the McGovern Institute, says that the reason for the interest in researching the phenomenon is due to the fact that it is a “common human experience,” explaining that “when a part of a person’s body hurts, he automatically rubs it. Because he knows that touch can relieve pain in this way, but it was It’s hard for neuroscientists to study the case.
Pain relief modeling
Pain relief through touch can begin in the spinal cord, where previous studies have found pain-responsive neurons whose signals weaken in response to touch. But there have been hints that there is a cycle in the brain as well.
This aspect of the response has been largely unexplored, Wang says, because it can be difficult to monitor the brain’s response to painful stimuli amid all the other neural activity going on there — especially when lab animals are moving.
So, while the team of researchers knew that the mice respond to a potentially painful stimulus on the temples by rubbing the face with the paws, they couldn’t follow the specific pain response in the animals’ brains to see if this rubbing helped calm them down.
rhythmic movement
But Wang says she and her colleagues have found a way around this hurdle. Instead of studying the effects of facial rubbing, they have focused their attention on a more subtle form of touch: the gentle vibrations produced by the movement of animal whiskers.
Mice use their whiskers to explore, moving them back and forth in a rhythmic motion known as flapping to feel their surroundings. This movement activates the touch receptors in the face and sends information to the brain in the form of vibrating signals.
The human brain receives the same type of touch signal when a person holds their other hand while it is being pulled from a painfully hot pan, another way in which a person seeks pain relief is through touch.
Get rid of the pain
Wang and her colleagues found that the movement of the whiskers can change the way mice respond to an annoying heat or a poke on the face — both of which normally result in face rubbing.
“Cells that respond preferentially to heat and pressure are less activated when the rats stroke, as they are less likely to show responses to painful stimuli,” Wang says.
Even when the flapping animals rubbed their faces in response to painful stimuli, the team of researchers found that neurons in the brain took longer to adopt the pain-calming patterns associated with the motion of friction and touch.
Thalamic pain syndrome
Wang points out that even in the fraction of a second before excited mice begin to rub their faces, when the animals are relatively still, it can be difficult to identify the brain signals associated with the perception of heat and pressure that trigger the whisker movement. So the researchers developed new computational tools and algorithms to differentiate the reaction of excited lab rats.
Wang says the new findings could shed light on a condition called thalamic pain syndrome, a chronic pain disorder that can develop in patients after a stroke that affects the thalamus in the brain.