Shimpei Ishiyama, Michael Brecht

While neuroscientists have been immensely working on diseases and emotional disturbances, positive emotions such as fun, laughter and happiness are poorly studied. Tickling is an interesting form of social touch that has intrigued great thinkers for more than two millennia. Despite the common appearance of tickling in human cultures, the mechanism of ticklishness or even its purpose and biological benefits remain elusive. In fact, not only humans but also other animals including non-human primates and rats emit playful vocalizations, i.e. laugh, when being tickled. I study the neuronal basis of ticklish sensation and tickling-associated behavior in rats. Our recent work revealed that neuronal activity in the deep layer trunk somatosensory cortex represents ticklishness in rats. These neurons are activated not only during the rat is tickled, but also during the rat is playing with my hand by chasing it, suggesting the neuronal link between tickling and play.