Contagious itching is hardwired in the brain
Have you noticed how when you yawn, the person you are talking to starts yawning too? And the same thing happens while itching? Watching someone itch can make you want to itch too.
For a long time we thought it was all in our mind. Apparently we are wrong.
A new study shows that behaviours like itching and yawning are hardwired in our brain and is not a form of empathy response.
Itching and yawning are socially contagious behaviours which mean that if one person does it the other will likely follow soon.
The contagious itching behaviour of mice is something that they cannot control as it is innate and instinctive.
Itching is a highly contagious behaviour and by studying mice, researchers found out what happens in the brain when a mouse feels itchy after seeing another mouse itch. This discovery helps scientists understand the neural pathways which control socially contagious behaviour.
For this study, the scientists put a mouse in an enclosure with a computer screen. They then played a video of another mouse scratching.
Within a few seconds the mouse in the enclosure started scratching too. This, the scientists found surprising as mice have poor vision and rely on smell and touch to explore areas.
The scratching behavior of the mouse means that it saw the video and the mouse which was scratching in it.
The researchers identified a structure called suprachiasmatic nucleus (SCN), a region of the brain that controls when animals fall asleep or wake up. The SCN was highly active after the mouse watched the video of the scratching mouse.
When the mouse watched the scratching mouse video and when placed near other scratching mice, the researchers noticed that the SCN would release a chemical substance called GRP (gastrin-releasing peptide) – a key transmitters of itch signals between the skin and spinal cord.
When the mouse sees another mouse scratching it does not think about scratching. Instead the brain sends an itch signal using GRP as a messenger.
To test this, the researchers used various methods to block GRP or the receptor it binds to on neurons. Mice whose GRP or GRP receptor was blocked in the brains’ SCN region, did not scratch when they saw other mice scratching. However they did scratch normally if they were exposed to itch-inducing substances.
The next time you scratch or yawn because you saw someone else doing it, remember that it’s not a choice or a psychological reaction. It is hardwired in your brain and that’s just the way it is.
Source: Science
