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Good vibrations and the science of touch
Pacinian corpuscles in the periosteum (the membrane around bones) of the lower leg of mice. Pacinian corpuscles are mechanoreceptors that are abundant in human palms and fingers, but in rodents they cluster in periostea. They are particularly sensitive to high-frequency vibration.
[Image courtesy of Hagen Wende and Carmen Birdmeier]
Did you know that your fingertips and palms are especially good at feeling vibrations? You can check this out by putting your hands on an object that's giving a gentle hum, like a washing machine. Then try your forearm, and compare what you feel.
The reason the skin on your fingers and palms is particularly sensitive to vibrations is because it's full of specialized nerve endings called Pacinian corpuscles. These are one variety of "mechanoreceptors" at the endings of sensory neurons. Mechanoreceptors detect stimuli, such as vibrations, and the neurons then fire signals to your brain, causing you to feel the sensation.
In a new study, researchers have identified a protein that helps Pacinian corpuscles grow and operate normally. Hagen Wende of Max-Delbrück-Center for Molecular Medicine in Berlin, Germany and colleagues discovered that mice with mutations in this protein had non-functioning Pacinian corpuscles. (Unlike humans, mice have most of their Pacinian corpuscles in a layer of tissue that surrounds their bones. So, the expression "I feel it in my bones" might really apply to mice!)
In rare cases, humans are born with the same mutation. The researchers studied four related people who had all inherited this mutation. These individuals were much less sensitive to vibrations than normal individuals, although they were able to feel other kinds of touch sensations normally.
Curiously, this protein, called c-Maf, also plays a role in eye development. When the protein is mutated it can cause cataracts. Scientists will have to do more research to understand what other roles this protein plays.
This research is being published online by the journal Science on 16 February 2012.