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11/10/2016 19:00

Why are we ticklish?

Ibou Diop Stabsstelle Presse- und Öffentlichkeitsarbeit
Humboldt-Universität zu Berlin

    A new study from the Humboldt-Universität zu Berlin has found how “ticklishness” is represented in the rat brain. The study has been published on 11th November 2016 in Science.

    Of all physical sensations, ticklishness is perhaps the most mysterious. Why do we laugh in response to tickling? Why are certain body parts more ticklish? Why cannot we tickle ourselves? Indeed, the mystery of ticklish perception has been discussed for more than two millennia by great intellectuals including Aristotle and Charles Darwin. Despite such long-standing interest, the mechanism of ticklishness remained elusive.
    The new study investigated tickling in rats. Earlier work had shown that young rats respond with 50 kHz ultrasonic “laughter-calls” to tickling by humans. In the novel study rats also reacted enthusiastically to the tickling: they emitted numerous calls. As judged by their calls, rats were most ticklish on the belly and underneath their feet. Rats often performed unsolicited joy jumps (Freudensprünge) after tickling, a behavior that can be seen in joyful subjects in various mammalian species. Rats also played with the researcher’s hand and chased it, and emitted similar calls during play.

    The researchers (Shimpei Ishiyama & Michael Brecht) then went on to investigate the response of the rat’s brain to such tickling. Specifically, the investigators studied the rat’s somatosensory cortex, a large brain structure that contains an ordered representation of the body and handles stimuli on the body. In the trunk region of the somatosensory cortex, the researchers observed nerve cells that responded strongly to tickling. Interestingly, the researchers found very similar brain responses during play behaviours as during tickling, even though the rats were not touched by the scientist. Making rats anxious – which reduces ticklishness ¬– also reduced the activity in these cells and suppressed the calls. Remarkably, rats emitted calls just to electric stimulation of the cells in the trunk region of the somatosensory cortex without being tickled. Taken together, these results suggest that activity in the trunk somatosensory cortex represents ticklish sensation.

    Professor Michael Brecht, who led the study, says: “The data much look like we identified the ticklish spot in the rat brain. I also find the similarity of brain responses to tickling and play remarkable. Perhaps ticklishness is a trick of the brain that rewards interacting and playing.”

    S. Ishiyama & M. Brecht, Neural correlates of ticklishness in the rat somatosensory cortex. Science (2016). http://science.sciencemag.org/cgi/doi/10.1126/science.aah5114

    More Informations
    https://youtu.be/1ukqZj9xWyk

    Kontakt
    Prof. Dr. Michael Brecht
    Humboldt-Universität zu Berlin
    Tel: 030 2093-6770
    michael.brecht@bccn-berlin.de


    Images

    Shimpei Ishiyama HU
    Shimpei Ishiyama HU

    None


    Criteria of this press release:
    Journalists, all interested persons
    Biology, Psychology
    transregional, national
    Research results
    English


     

    Shimpei Ishiyama HU


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