What is the scientific reason behind the human likes to contact?

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It is a scientific consensus that physical contact will bring pleasure - people have a natural need for physical touch.

Physical contact has a positive effect on trust and cooperation, disarms people, increases their sense of security, and calms tension . Many studies have concluded that touching, especially hugging, reduces stress levels and regulates hormone levels in the body. Touching other people's bodies or shaking hands can be beneficial for emotionally anxious people.

For example, when a patient arrives at the hospital for surgery, if the medical staff can gently touch the patient's forehead or shoulder, it will soothe their anxiety. But for a long time, scientists didn't know the reason behind the pleasure that touch triggers in people.

This week, in a research paper published online by the top journal "Science", a research team led by Chinese scientist Professor Chen Zhoufeng revealed the mystery behind it . In this new study, Professor Chen Zhoufeng's team found that, similar to the "itch" sensation, pleasant touches such as caressing and patting have specialized neural circuits and chemical messengers responsible for transmitting signals from the skin to the brain .

Specifically, the researchers devised a clever experiment to examine the touches experienced by mice . Mammals are mostly social animals, and artificial isolation will make people or animals have a strong desire for contact. Based on this principle, they first isolated the mice individually for a period of time. The mice were then given a "massage" in a specific cage: gentle brushing of the mouse's back with a soft-bristled brush.

Using this method, the research team began to look for neural signals in mice that would be activated by hair brushing, and thus found the key neuropeptide substance PROK2 in sensory neurons . PROK2 acts as a chemical messenger that encodes the pleasant touch and transmits the signal to spinal interneurons with the corresponding receptor PROKR2, which transmits the signal to the brain.

In this study, the scientists created mice without the neuropeptide PROK2, or mice lacking the receptor PROKR2 in neurons of the spinal cord, using biotechnological means such as gene knockout. These mutant mice still had normal responses to other tactile stimuli such as itching and pain, but were unable to sense pleasant touch signals.

As a result, the mice displayed a series of "social fear" behaviors. For example, under normal circumstances, mother mice like to lick their pups, and adult mice often groom each other. However, mice with defects in the PROK2-PROKR2 neural circuit were resistant to all of these things, not willing to offer physical contact, but also flinched and avoided when their peers tried to interact.

Lacking friendly physical contact with their peers, these island-like mice developed hyper-anxious and stress-responsive behaviors not found in normal mice.

In conclusion, these experiments revealed the positive feedback mechanism behind people's need for touch, and found neurons that can regulate social behavior from neural circuits, which may be used as targets in the future for autism, mental health Patients with schizophrenia, post-traumatic stress syndrome and other diseases bring new treatment options.