Stroking reveals pleasure nerve

A new touch-sensitive nerve fibre responsible for the sense of pleasure experienced during stroking has been described at a UK conference today.

The nerves tap into a human's reward pathways, and could help explain why we enjoy grooming and a good hug, a neuroscientist has explained.

His team used a stroking machine to reveal the optimal speed and pressure for the most enjoyable caress. ...

In order to isolate the touch-sensitive nerves responsible for the pleasure experienced during stroking, Professor McGlone designed a "rotary tactile stimulator" - a high-tech stroking machine. "We have built some very sophisticated equipment, so the stimulus [of stroking] is very repeatable.

"We stroke the skin [of the forearm, foreleg, and face] with a brush at different velocities, and then asked the volunteers to rate how they liked it," he explained. He also inserted microelectrodes through the skin, into a nerve, to record the neural signals running from the skin to the brain.

"It is like tapping a single phone-line and listening for the chatter that comes down that line," he told the conference. ... The Liverpool-based researcher showed that stroking speeds of about 5cm per second, while applying 2g of pressure per square cm is optimal, and gave the volunteers most pleasure.

He explained that the pleasure messages are conveyed from the skin to the brain, by similar types of nerve fibres as those that transmit the sensation of pain. "This is interesting as we often rub a pain to try to alleviate it," he said. ...

Stroking could be used to treat chronic pain, he suggests. - bbc

5cm per second, with 2g of pressure per square cm, eh? That's slow. According to this research, max pleasure happens at a slow rate of a few seconds per inch with about the weight of a pencil.

A pencil weighs about 2 grams.

Odd trivia: A human soul weighs 21 grams, according to one questionable study.