Even tickle it takes the right mood

Darwin said that to experience pleasure from tickling we have to be in the mood. Confirmation that it really is that comes from a group of researchers who made a curious experiment with rats, identifying the area in the brain linked to the feeling of tickling.

MYSTERIOUS SENSATION. According to the father of the theory of evolution, the laughter

provoked by tickling comes from the anticipation of pleasure, but in the Middle Ages prolonged tickling was a form of torture. Thinkers, philosophers and scientists, from Plato to Galileo, have ventured in an attempt to understand its nature. But even today, despite we know well the feeling, you know little or nothing of how you generate in the brain, of what function, and why the sudden twist in certain parts of the body sometimes makes us laugh and jump on other occasions is annoying, and some do nothing.

ALSO RATS LAUGHING. Two researchers Humboldt University (Berlin), Shimpei Ishiyama and Michael Brecht, have tried to understand something more since the rats. Even these animals, in fact, as it was understood by previous research, have their "laughter", which although is not audible to the human ear (because emitted ultrasound), can be easily measured. Doing various tests tickling the animals, in different situations, the scientists were able to draw some conclusions, reported in an article published in Science (abstract in English).

Below, the video of one of the tests with the trace of ultrasound, which have also been transposed to make them audible.

BALZI JOY. The first is that, as in many cases to humans, tickling is also pleasing to the animals, jumping and laugh when they are tickled vigorously on his stomach and on the back, and they approached to seek the hand that has tickled, after they have tried it the first time.

In addition, by measuring the activity of neurons in the somatosensory cortex sensitive animal, the part where it is received the feeling of touch, the researchers saw that his activities, especially in the deeper layers, increased - neurons "firing" of more - while the animals were tickled. And confirming that that is precisely the point where the brain generates the feeling, stimulating neurons without doing anything, the researchers induced in rats the same giggles and jumps when scratching the belly to animals.

BLOCKED BY FEAR. But when the rats were in a situation of anxiety, for example, raised on a platform which they were not accustomed, tickling did effect: there were no jumps or laughter. A confirmation that tickling is a very old form of physical socializing, linked to the game, and that negative emotions can inhibit the sensation in the brain.