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Scientists map out the 'emotional body'

By Tim Sandle     Nov 29, 2014 in Science
Liverpool - Scientists examining neurons that respond to gentle touch has shown that people find strokes on another person's back and shoulder more pleasurable than strokes to the forearm and hand. This has led to the creation of an "emotional map" of the human body.
The basis of the map is as follows: human skin has two different ways of sensing its environment. One way is through relatively large, fast discriminative touch nerve fibers that detect objects and the second way is through smaller, unmyelinated C fibers that are typically associated with itch or touch. Simply put, one part is about sensing the world and the other part is about feeling.
As the basis of the "emotional map", one type of C fiber, called C-tactile afferents (CTs), is specifically dedicated to the sensation of gentle touch, responding most strongly to strokes around 3 to 10 centimeters/second.
It has been found, according to The Scientist, that in humans there are no CTs on the palms of their hands or the soles for their feet. However, elsewhere the distribution of these fibers throughout the body is largely unknown.
To explore this further, scientists based at Liverpool Johns Moores University in the U.K. asked participants to rate the pleasantness of static, slow, and fast touches as they viewed them being applied to the back, shoulder, forearm, or hand of a person on a video screen.
It was found that slow touches to the back and shoulder were rated the most pleasant, while slow touches to the forearm were less so. In all three locations, participants rated slow touches as more pleasurable than fast or static touches. On the palm where no CTs exist, slow strokes were not perceived as more pleasant than static touch.
From the study, the scientists propose an emotional homunculus linked to the body's discriminative touch neurons. In other words, an "emotional map" of the human skin. Lead scientists Susannah Walker said in a research summary: "The degree of pleasure derived from a gentle touch is linked to the distribution of a specialized type of nerve fiber."
The results were recently presented at a meeting of the Society for Neuroscience (SfN) conference in Washington, DC.
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