Finding the Brain's Funny Bone

Strong physician maps our response to a good laugh

November 27, 2000

"Top Ten Dumb Guy Ways To Solve Presidential Election Confusion"

No. 6 - Do what they do in other important contests in Florida: swimsuit competition.

No 2 - Let my brother Jeb decide.

No. 1 -- Solve it? Are you nuts? This is great!

If you chuckled at these lines from a classic Top Ten list by David Letterman, stop for a moment and consider why.

Philosophers have been asking questions about laughter for thousands of years - and now a University of Rochester Medical Center radiologist has found the brain's "funny bone."

Dean K. Shibata, M.D., has discovered that humor appreciation - our ability to recognize a joke - appears to be based in the lower frontal lobes of the brain. It is the first study that captures images of the brain, using functional magnetic resonance imaging (FMRI), to determine what areas become active when we experience something humorous.

Shibata, an assistant professor of Radiology at URMC and principal investigator for the study, will present his findings today in Chicago at the annual meeting of the Radiological Society of North America. The RSNA has chosen Shibata's project as one of a handful to be highlighted for more than 30,000 meeting participants.

"Why do we laugh? No one really knows," Shibata said. "But knowing which areas of the brain are involved gives us an idea of how humor is processed, what functions it may be related to, and ultimately how it may have developed. This is important because it provides insight into social and emotional behavior, and how we communicate and foster relationships."

Connecting the brain's response to humor, which plays a powerful role in shaping our personalities, is significant for many reasons:

  • It could aid physicians in diagnosing and treating patients with mental illness or mood disorders such as depression, by showing the brain's response to positive stimuli. Traditionally, research has focused on the brain's response to negative emotions such as fear.
  • It could provide surgeons with valuable pre-operative mapping of the brain areas critical for maintaining the emotions and social behaviors that make up our personalities.
  • It advances science, proving the value of new and sophisticated tools that can provide glimpses into the brain and how it works.
  • It helps to demonstrate that mental activity, even one as evanescent and complex as humor, has a physical correlate.

Other studies, involving stroke and seizure patients, have tried to correlate brain abnormalities with either uncontrollable laughing episodes or a loss of the sense of humor.

But in Shibata's research, MRI scans were performed on 13 normal volunteers in a series of four exams. The scans directly visualized what parts of the brain were involved when the subjects read written jokes, viewed cartoons and listened to digital recordings of laughter.

The MRI scans showed that when the subjects saw the jokes and cartoons - tasks that require a decoding of the humorous stimuli - the brain activity was most prominent in the ventromedial frontal lobe. This suggests that the frontal lobe is responsible for telling us what's funny.

But when they heard laughter and laughed along internally, a response known as contagious laughter, the activity was centered in the anterior supplemental motor area. That part of the frontal lobe near the top of the brain is normally associated with planning complex movements and initiating speech. All four scans also showed activity in a small spot at the base of the brain, called the nucleus accumbens, an interesting area associated with positive emotions in animals and identified as a key site in moderating drug addiction. Activity in the nucleus accumbens is likely related to our feeling of mirth after hearing a good joke and our "addiction" to humor, Shibata said.

Co-authors of the paper being presented by Shibata are Jianhui Zhong, Ph.D.; Edmund Kwok, Ph.D.; David A. Shrier, M.D.; Yuji Numaguchi, M.D., Ph.D.; and Henry Z. Wang, M.D., Ph.D., all of the University of Rochester Medical Center Department of Radiology.

(Note: The MRI Center at URMC's Strong Memorial Hospital is the only facility in western New York performing clinical and research functional brain studies that allow rapid mapping of the brain's activity in a variety of settings. Researchers can form a movie picture of the brain as it works without radiation or injections.)

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Leslie Orr
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