You gotta love popular culture. Even a lab nerd like me can have his 30 seconds of fame on late night network TV. Here’s the strange and convoluted tale of how it went down (not for the faint of heart).
In The Accidental Mind I wrote the following:
The cerebellum is also important in distinguishing sensations which are “expected” from those which are not. In general, when you initiate a movement and you have sensations which result from that movement, you tend to pay less attention to those sensations…This may all sound a bit abstract, but let’s consider an example. It is well known that you can’t tickle yourself. This is not just a phenomenon of certain cultures, it is present all over the world. What’s different about having someone else tickle you, which can result in a very strong sensation, and self-tickling, which is ineffective? When researchers in Daniel Wolpert’s group at University College London placed people’s heads in a machine that can make images showing the location and strength of brain activity and then tickled them, they found strong activation in a brain region involved in touch sensation called the somatosensory cortex and no significant activation in the cerebellum. When people were then asked to tickle themselves on that same part of the body, it was seen that there was a spot of activation in the cerebellum and reduced activity in the somatosensory cortex. The interpretation of this experiment is that commands to activate the hand motions in self-tickling stimulated the cerebellum, which then formed a prediction of the expected sensation and sent signals encoding this prediction to inhibit the somatosensory cortex. The reduced activation of the somatosensory cortex was then below the threshold necessary to have the sensation feel like tickling. Interestingly, there are now reports that some humans who sustain damage to the cerebellum cannot generate predictions of expected sensations and therefore can actually tickle themselves!
Sharon Begley, writing in Newsweek, picked this up and penned:
Let others rhapsodize about the elegant design and astounding complexity of the human brain—the most complicated, most sophisticated entity in the known universe, as they say. David Linden, a professor of neuroscience at Johns Hopkins University, doesn't see it that way. To him, the brain is a "cobbled-together mess." Impressive in function, sure. But in its design the brain is "quirky, inefficient and bizarre ... a weird agglomeration of ad hoc solutions that have accumulated throughout millions of years of evolutionary history," he argues in his new book, "The Accidental Mind," from Harvard University Press. More than another salvo in the battle over whether biological structures are the products of supernatural design or biological evolution (though Linden has no doubt it's the latter), research on our brain's primitive foundation is cracking such puzzles as why we cannot tickle ourselves, why we are driven to spin narratives even in our dreams and why reptilian traits persist in our gray matter.
This somehow led to the following exchange on The Tonight Show on Tuesday April 3
Jay Leno: Neurological researchers at Johns Hopkins University are now investigating the phenomenon of why we cannot tickle ourselves. You know that? You cannot tickle yourself?
Kevin Eubanks: Really?
Jay Leno: Try it. You cannot tickle yourself. I’m so glad that AIDS and cancer have been cured so that we can move on.
Kevin Eubanks: You spend a lot of time tickling yourself? [Rim shot]
Jay Leno: I’m not working on it!
Click here to download an MP3 of the Jay Leno self-tickling dialogue (~ 30 seconds of audio)