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Scope Series 4 RTÉ Two, Thursday, 7.00pm

Brain function and humour

Dr. Hugh GaravanWould you find it funny that there’s a specific name for the physiological study of laughter? It’s certainly no laughing matter to gelotologists – scientists seeking to explain exactly what happens to our minds and bodies when we crack up.

What we do know is that certain parts of the brain are responsible for certain human functions. For instance, emotional responses such as anger, love and sorrow are the function of the brain’s largest region, the frontal lobe. However, when it comes to laughter there’s no single area of the brain in charge.

Instead, laughter is an extremely complicated human response. It requires the brain to take in and process both visual and auditory information before tickling the motor centres of our central nervous system. This produces responses as varied as a giggle, guffaw or great big gut-busting spasm.

In this segment Scope joins Dr. Hugh Garavan of Trinity College’s School of Psychology and Institute of Neuroscience to take a peek at what happens to the brain when we laugh.

MRI scanEver heard a joke but didn’t really get the punch line until several seconds or minutes later?  That just illustrates how complicated – and time consuming - our responses to humour can be.

We all know humour isn’t universal. A joke that’s hilarious to one person falls flat for another. This illustrates how complex a sense of humour – or lack thereof - is throwing yet another curve ball at researchers trying to study laughter.

Since laughter involves so many different areas of the brain scientists are just getting to grips with the response, even with recent advances in medical imaging, most notably magnetic resonance imaging (MRI).

The MRI machine uses a magnetic field and radio waves to produce a detailed picture of what exactly happens inside the body or brain.

At any given moment, one thin cross section, or “slice” can be captured. More importantly, MRIs are non invasive and do this without damaging the brain being studied or causing pain to the subject.

What MRIs have shown medical researchers is that the limbic system, located below the brain’s cerebral cortex, is heavily involved in laughter.

Sometimes called the reptilian part of our brain, the limbic system controls basic human urges such as hunger and responses to danger as well as motivation and emotional behaviours.

Two different parts of the system are involved in laughter; the amygdala, a small almond-shaped structure deep inside the brain, and the hippocampus, a tiny, seahorse-shaped structure. 

However, the limbic system doesn’t act alone in the case of laughter. When the laughter is loud and uncontrollable, then researchers know the hypothalamus, sometimes called the “master gland” which links the central nervous system to endocrine system, has joined the party.

 

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