The mystery of human proprioception

  Proprioception is the mysterious ability of the body to perceive the position of the limbs. This feeling can be fully displayed even in the dark. But until today, scientists have just begun to understand it.
  Lost a related experiment
  let’s do a little experiment: put a cup in front of you, now please open eyes with your fingers touch the cup several times to determine the position of the cup, then close your eyes and try again, See if you can find the position of the cup. Believe that this task will not have any difficulties for you.
  You might pouting and saying, “There will be no difficulty for anyone.”
  Don’t think about it this way. For some people, the difficulty is great. In a similar test, a woman named Sana in France was completely confused. The test is like this: Place a table in front of her, a cylinder on the table, and a plastic ball on the top of the cylinder. She must first touch her nose with her finger, and then touch the plastic ball with her finger, in order to determine the position of the nose and the plastic ball. When you do it with your eyes open, everything is okay. Then, the researcher asked Sana to close her eyes, put the latter’s finger on the plastic ball, and then moved her nose back to let her close her eyes and feel the position of the nose and the plastic ball, and finally let go and ask her to continue Close your eyes and do this again by yourself. As a result, the position of the plastic ball suddenly disappeared from Sana’s mind. She fumbled around, waving her arms left and right. When she managed to catch the plastic ball, it looked like she was lucky. She even had difficulty locating the nose on her face, and she couldn’t find the right position at all several times.
  ”It feels like being lost,” Sana told the experimenter. When her eyes were closed, she didn’t even know where her body was in space.
  Loss of proprioception people
  after we close our eyes to perceive the world and the body position and will not disappear. This feeling is called “proprioception”, which is a kind of awareness of the position of the limbs and the position of the body in space. Like other senses (sight, hearing, etc.), proprioception also helps our brain navigate. Scientists sometimes call it the “sixth sense.”
  Proprioception differs from other sensations in one key aspect: the eyes can be blind, the ears can be deaf, and there are many people who are blind or deaf; but proprioception is never closed, with very few exceptions.
  Sana is one of the few people whose proprioception is turned off, as is her sister Thorson. At home, if the lights were suddenly turned off and Thorson happened to be standing, it would be difficult for her to find a chair to sit down. It was as if someone had blindfolded her, made her rotate a few times, and then let go. She couldn’t tell the east from the west.
  The sisters also have another weird characteristic: no sense of touch (what they lack, strictly speaking, a slight sense of touch, as we will see below), many things they touch cannot be sensed. Even if you touch the ball with your eyes open, you can’t feel its existence.
  Of all the senses, touch and proprioception are probably the least we know. However, in the past ten years, neuroscientists have made major breakthroughs in the work of these two senses, which helps us to understand the body’s experience of the world more comprehensively.
  Small molecules, powerful
  Carsten Boni Man is an American neuroscientist. In 2015, he examined a woman with a strange disease. This woman was 18 years old and she only learned to walk when she was 7. Now, she can only walk by looking at her feet, and if she is allowed to stand with her eyes closed, she will fall to the ground. In other words, she can maintain her body balance only when she opens her eyes.
  When Poniman checked her, he realized that she had no proprioception. Besides, with her eyes closed, she could not feel the doctor gently moving her fingers. This loss of tactile sensation does not only appear in her fingers, elbows, shoulders, and hips, she can’t feel any joints in her body.
  In order to find out why this symptom appeared, Poniman’s team sequenced the woman’s entire genome and found that in her, a gene responsible for a tactile sensor called “piezo2” had a mutation, leading to The piezo2 tactile receptors throughout the body have failed.
  Various receptors play an important role in us. For example, if we want to be able to see light, we have to rely on visual receptors; to smell, we have to rely on olfactory receptors in the nasal cavity… After the receptors are stimulated, they generate electrical signals, and the electrical signals travel along the various nerves connected to them (such as Connected to the visual receptors is the optic nerve (optical nerve) which is transmitted to the brain, and the external world can be perceived by us. If nerves are the wires that transmit information from the outside to the brain, then these receptors are the places that convert external stimuli into electrical signals.
  Researchers have discovered two new tactile receptors: piezo1 and piezo2. When the cells containing these two receptors are squeezed and stretched, the piezo receptor is stimulated to release electrical pulses. There is a division of labor between the two. The piezo1 sensor “mainly inside” is responsible for monitoring the squeezing from the body, such as blood pressure; the piezo2 sensor “mainly outside” is responsible for feeling the squeeze from the outside of the body. Further research shows that the piezo2 receptor is a molecule that is very important for touch and proprioception. It is a door. Only after this door can the external squeeze be perceived by us.
  Like Poniman’s patients, Sana and Thorsen were born with a genetic mutation that caused piezo2 to fail. This caused them lifelong proprioception, touch and movement disorders. They can only walk a little, and they can only use electric wheelchairs if they want to go around like normal people. They have never experienced a life with proprioception at all, and they think that everyone is the same as them, until they are tested that they are different.
  So far, researchers have found 12 cases of piezo2 sensor failure.
  The mystery of the human sense of touch
  comes proprioception, we can not but talk about our sense of touch. Because of all sensations, touch and proprioception are the closest, and even some of the functions of the two overlap.
  Human touch is a very complex sensation, because it has many forms, each of which relies on a slightly different nervous system and sensory system.
  For example, the sensation of cold and heat and the sensation of light touch involve different nerves, and the receptors used are also different. The nerves and receptors involved in itching and touching are also different. In addition, there are some touches depending on the environment. Think about this situation: the longer you wear a certain T-shirt, the weaker your body feels about it, so you are less aware of its existence; but wearing the same T-shirt after sunburn, you may I felt its existence again.
  The two sisters, Sana and Thorson, without piezo2, could not perceive slight touches, especially those acting on their hands and fingers. For example, they often put their hands in their wallets and then pull them out when they feel they have something in their hands, only to find that they have not got anything.
  However, they can feel cold and hot, as well as pain. It is worth noting that they can still feel the tingling—the tingling is a sensation produced by touch, and it is logically impossible for them to feel it.