In the brain to someone else’s itch-responsive regulator of circadian rhythms.

Humans and animals can infect each other yawn: if someone in the company gave a yawn, then starts to yawn, and others. The same goes for carding: if, for example, the mouse will see how scratching her comrade, then she will start to itch.

(Photo: Tharakorn /

The phenomenon of contagious behaviour is very interested in the psychologists – it is believed that the ability to succumb to someone else’s yawn or scratching evidence of empathy, the ability to adopt the feelings of another. The fact that a yawn can catch each other monkeys, rats, birds, dogs (and dogs can catch a yawn even from the owners), says that there is empathy in animals.

But, as in the case of any psychological phenomenon, contagious behavior must conform to certain processes in the brain. If we talk about the scratching, it can be assumed that the one who looks at itchy, he feels itchy . However, as shown by the experiments researchers from the University of Washington, everything is a bit wrong. Zhou-Feng Chen (Zhou-Feng Chen) and his colleagues planted the mouse in a cage with a screen on which was shown a video with another mouse that itched. Rodents-the”audience” started to scratch herself behind – despite the fact that the vision of mice is not too good, and neither smell nor touch, itchy friend on the screen, they could not.

In an article in Science the authors write that after watching “the itch” live in the animal brain activated area called the suprachiasmatic nucleus. About it is usually remembered, when we are talking about the biological clock because it is known that the suprachiasmatic nucleus is one of the main regulators of circadian rhythm and evening gives the entire body “to sleep”. But obviously he also has other functions associated with the phenomenon of contagious behavior.

It turned out that in mice, when examined prochesyvayuschie friend suprachiasmatic nucleus threw out a lot of neuropeptide GRP (gastrin-releasing peptide). This neuropeptide, on the one hand, signals the secretion of digestive hormone gastrin (which activates digestion), with another – the same GRP are needed to pass the “itchy” nerve impulse from the skin to the spinal cord. Moreover, GRP was required in order to become infected with scabies when animals with special substances to cut off the buds to him, they ceased to respond to someone else’s itch, but that itch safely if they felt itching.

The authors believe that the contagious behavior occurs regardless of the will of the individual, and it is impossible to control (and everyone who was yawning, the company quite agree with this). The mechanism that allows that behavior to spread throughout the group, built right into the brain and looks quite simple – one signal plus neuropeptide receptor to it.

However, it is unlikely that the neuropeptide and receptor need only to infect each other with the itch or yawn, it would also be curious to know what kind of signal molecular and cellular mechanism triggered by yawning, the same or different.