If you have ever laughed at a joke despite not finding it funny, or laughed at something and weren't sure why, you have proven that comprehending and appreciating humour are two very different things. Western University neuroscientists have now discovered that two distinct parts of the brain trigger these reactions, a result that also may shed light on why some patients with Parkinson's disease might have difficulty being 'in' on a joke.
For the study, healthy participants were examined in a functional magnetic resonance imaging (fMRI) scanner while listening to a series of audio-recorded jokes and watching an episode of the classic TV series, Seinfeld.
Maggie Prenger (Maggie MacLellan photo)
"It was very easy to find participants," said Schulich School of Medicine & Dentistry MD/PhD student and study lead author Margaret Prenger. "Who doesn't want to lie down for an hour in a cozy MRI and watch Seinfeld?"
During the fMRI scan of the healthy participants, two distinct regions of the brain showed increased activity when a joke's punchline was delivered or Jerry, George, Elaine or Kramer said or did something funny. The dorsal striatum, a brain area involved in working memory, processing ambiguity and cognitive flexibility, fired up, indicating the joke was understood or the participant 'got it' and shortly after that, the ventral striatum, critical in reward-processing and enjoyment, ignited too, showing they thought the punchline or moment was funny, or at least they appreciated the humour.in
"Our main hypothesis is that these different sub-regions of the striatum are involved in humour comprehension and humour appreciation," said Prenger. "And potentially, depending on different neurodegenerative diseases like Parkinson's or other damage to particular areas of the brain, one of those processes could be affected in some patients while the other one is spared."
The study, published in The Journal of Neuroscience was funded by Western's neuroscience research initiative BrainsCAN.
Potential impact for Parkinson's
To test that theory, next Prenger, under the co-supervision of Schulich Medicine & Dentistry faculty Dr. Penny MacDonald and Adrian Owen, and her collaborators scanned patients with Parkinson's disease with the audio-recorded jokes and Seinfeld viewings. Their early data indicates that the dorsal striatum, or comprehension processor, did not react as expected, while the ventral striatum, or appreciation processor, for the most part did. These results have yet to be published.
"We think the reward area is potentially motivating the humour comprehension process, which makes sense because our brains expend a lot of energy trying to figure out the world and your brain doesn't want to expend it on things that don't matter," said Prenger.
Future studies from this group will look at the effects of dopaminergic medications on humour comprehension and appreciation processes.
"It makes sense that if you are dopamine-depleted, as patients with Parkinson's disease are, they may not understand things that are funny," said Prenger. "Colloquially, dopamine is known as the reward chemical, and it might provide this motivation in anticipation of feeling amused by a joke."
