What happens when you see someone scratch a mosquito bite? You may start to feel an itch come out of nowhere. Then you might start to scratch, too. Mice, new data show, suffer the same strange phenomenon. It’s called contagious scratching.
Tests with mice provide the first clear evidence that contagious scratching can spread mouse-to-mouse, says Zhou-Feng Chen. As a neuroscientist, he studies the brain. He works at the Washington University School of Medicine in St. Louis, Mo. His mice started scratching after watching an itchy neighbor. They even did this after just watching videos of scratching mice.
In discovering this, “there were lots of surprises,” Chen notes. One was that mice would even pay attention to some scratching neighbor. After all, mice are nocturnal. They mostly sniff and use their whiskers to feel their way through the dark. Yet Chen had his own irresistible itch to test the “crazy idea: that mice might share an urge to scratch, he says. And it paid off.
The quirk isn’t just a weird little finding, though. It opens new possibilities for exploring the basis in the brain for picking up such contagious behaviors.
Chen’s group described its new discoveries in the March 10 issue of Science.
How they did it
The researchers housed mice super-itchy mice within sight of some that didn’t scratch much. Then they recorded the animals on video. Shortly after a normal mouse looked at a neighbor scratching, it scratched, too. For a comparison, researchers gave others of these mice a not-very-itchy neighbor. These comparison mice also looked at their neighbor now and then. Rarely, however, would they scratch right after that glance.
And the neighbor didn’t have to be real. Sometimes it was just a mouse video. Animals that viewed the video of scratchers responded the same way. More audience itching and scratching followed the film of a mouse with itchy skin than one…