You might be wondering, why am I ticklish? Or, why do I laugh if somebody else tickles me, but not when I try to tickle myself? The mystery of ticklishness has been sought after for decades, including by Darwin and Aristotle.
A recent study tested ticklishness on rats, and the results were astonishing! The rats reacted to human tickles with ultrasonic “laughter cells” and emitted various calls. While many humans are most ticklish on their armpits and stomachs, rats were found to be most ticklish on their bellies and underneath their feet. They performed “joy jumps” after being tickled, which is a behavior associated with joyful subjects in various mammals.
Researchers continued searching for answers, and sought to discover how being ticklish relates to the brain and whether or not it is a trick of the brain that rewards interacting.
When researchers Shimpei Ishiyama and Michael Brecht investigated the response of the rat’s brain to tickling, they observed nerve cells that responded strongly to tickling and they found very similar responses during play behaviors as during tickling- even without the scientist touching the rat. These nerve cells also worked in reverse. For example, if the rats were made anxious, they were less ticklish and the activity in these cells were reduced. It was discovered that activity in the trunk somatosensory cortex is what led to ticklishness.
The discovery of the connection between brain responses to tickling and play was incredible.
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