New Delhi: Scientists have found that high-frequency neural activity, seen in tasks that require a lot of cognitive engagement, such as work, is also a mark of humour appreciation. The scientists from Institut Du Cerveau (Paris Brain Institute), France, and Bar-Ilan University in Tel Aviv, Israel, studied the cognitive and neuronal mechanisms on which appreciation of humour was based. They have described their findings in the journal Neuropsychologia.
Previous studies have shown the involvement of the temporal lobe in the processing of droll stimuli, or stimuli associated with goof. The scientists analysed intracerebral electrophysiological recordings of 13 epileptic patients, which made it possible to look at neuronal activity directly with a high spatial and temporal precision (at the millisecond scale) in several cortical areas.
So far, the preferred technique for these studies was fMRI. However, the researchers of this study said, the signal obtained via fMRI does not allow the detection of the entire spectrum of electromagnetic waves generated by the brain: part of the information is lost. The patients being studied had been implanted with deep brain electrodes as part of a pre-surgical assessment of refractory epilepsy.
The researchers asked the patients to watch a three-minute excerpt from Charlie Chaplin's Circus (1928) while their brain activity was measured live. Beforehand, the amusing nature of each sequence had been evaluated, frame by frame, by a group of healthy volunteers. The team then compared the patients' neural activity recorded during the funniest scenes in the film with that recorded during the least funny scenes.
"We observed that the funniest sequences were associated with an increase in high-frequency gamma waves and a decrease in low-frequency waves. "These results indicate that high-frequency neural activity, which is seen in tasks that require a lot of cognitive engagement, such as work, is also a mark of humour appreciation.
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"Conversely, scenes that are not funny, such as transition sequences where the character moves from one place to another without doing anything, promote inattention and introspection... and a preponderance of low frequencies," explained Vadim Axelrod, who led the experiment.
More importantly, the scientists said, this inverse relationship between high and low frequencies was observed in temporal lobe regions but not in others. It seemed that humorous content was not processed in the same way throughout the cortex and depended on brain areas and functions.
According to a dominant theory, the treatment of humour is based on two complementary mechanisms and involve two neural circuits - cognitive and emotional. Cognition is first employed to detect an incongruous element of reality. For example, in Charlie Chaplin's The Gold Rush (1925), the hero eats shoelaces like spaghetti.
Following this, a positive emotion related to this incongruity emerges through the emotional neural circuit. What is funny would, therefore, be both unexpected and pleasant. "Our results support this theory, as we confirm the prominent role of the temporal lobe in the appreciation of humour.
"As the anterior parts of this area are involved in semantic memory, we can imagine that their activity is linked to the analysis of the scene and the detection of its incongruous content. "Conversely, the activation of its posterior parts could correspond to understanding the unusual and, therefore, amusing aspect of certain social interactions," said Vadim Axelrod. (PTI)
