BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: tickle

Tickle, Tickle!

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.

 

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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.

 

Other Articles About This Topic:

http://www.npr.org/sections/health-shots/2016/11/10/501447965/brain-scientists-trace-rat-ticklishness-to-play-behavior

https://www.washingtonpost.com/news/speaking-of-science/wp/2016/11/11/watch-rats-giggle-and-jump-for-joy-at-being-tickled/

Are Rats Ticklish?

Up until now, ticklishness has been a mysterious physical sensation.  Michael Brecht, professor at the Humboldt University of Berlin and Animal Physiologist, headed a research project along with Shimpei Ishiyama to help understand the sensation of tickling. Many questions have been asked about this mysterious physical sensation for many years without sparking answers. Even Aristotle and Charles Darwin were curious about tickling. Why are certain body part more ticklish than other? Why does the body react with smiles and laughter? Why can you not tickle yourself? Can other animals be ticklish as well?

Tickle Tickle

This image was originally posted to Flickr by Yogi at http://flickr.com/photos/34427468531@N01/113215143

Turns out, rats are ticklish too! (Click HERE for video!) In the Study, Brecht and Ishiyama, tickled the rats.  The subjects responded really well to the researchers tickling them, emitting “laughter-calls” and playfully chasing the the researcher’s hand.  The calls are ultrasonic and can not be heard by the naked human ear.  According to their laughter calls and the “unsolicited joy jumps” after being tickled, the rats are most ticklish on their bellies and on the bottom of their feet.  Brecht observes, “It’s remarkable the similarities between rats and humans – the fact they vocalise and clearly enjoy tickling so much.”  

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British Pest Control Association

To further the research, Brecht and Ishiyama studied the brain to see what area of the brain reacts to tickling.  Cells are activated in the somatosensory cortex of the brain causing the rats to giggle.  The somatosensory cortex is part of the brain that registers touch and Brecht remarks that “we managed to pinpoint the ticklish spot in the brain.” During this study, they were able to discover that rats ticklishness is dependent on their mood.  Rats response to being tickled was far less measurable when the rats were stressed  This finding could lead to very important future research on the brain because there has been little research about how moods affects the brain.  

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