New research that utilized intracranial recordings in human patients provides unique insights into the neural mechanisms underlying humor processing. The study, published in Neuropsychologia, found that high-frequency brain waves increased during the funniest scenes in a Charlie Chaplin clip.
Researchers were interested in studying humor and its neural mechanisms because humor plays a crucial role in human interactions, stress reduction, and overall well-being. However, humor is highly subjective and influenced by culture, era, and context, making it challenging to generalize how humor works. The researchers aimed to understand the cognitive and neuronal mechanisms underlying humor and how different brain regions are involved in processing humorous stimuli.
“Humor plays a valuable role in our life,” said study author Vadim Axelrod of the Gonda Multidisciplinary Brain Research Center at Bar Ilan University. Humor can be beneficial for interpersonal communication. It might be also beneficial for individual psychological and physiological states by reducing stress. Despite humor’s important role, the cognitive and particularly neural mechanisms are poorly understood.”
Previous research using functional MRI (fMRI) has provided insights into humor processing, but fMRI has limitations in capturing the full spectrum of brain activity. In this study, the researchers used intracranial local field potential (LFP) recordings, which allow for direct measurement of neuronal activity with high spatial and temporal precision.
During an LFP recording, small electrodes are placed directly on or inside the brain tissue to measure electrical signals. The electrodes detect the changes in electrical potentials resulting from the synchronized activity of nearby neurons.
For the study, a 3-minute segment from the comedy film “Circus” (1929) featuring Charlie Chaplin was used as a stimulus. The researchers had an independent group of healthy participants continuously rate the funny moments in the movie segment . The aim was to identify the funniest and least funny periods of the movie, which would later inform the analysis of the neural data.
Axelrod told PsyPost he was impressed by “the universality of Charlie Chaplin humor. There was large agreement across participants as to which parts of the movie were funny.”
Thirteen patients with epilepsy were involved in the experimental portion of the study, having undergone deep brain electrode implantation as part of their pre-surgical assessment. They watched the same 3-minute movie segment while their neuronal activity was recorded.
The findings of the study revealed consistent involvement of the anterior temporal lobe, the temporo-parietal junction, and the temporal-occipital sulcus in humor processing. These regions exhibited frequency-specific responses to humorous stimuli. Different frequency bands, such as delta, theta, and gamma oscillations, were modulated during the perception of humor.
The researchers found that during the funniest scenes, there was an increase in high-frequency brain waves and a decrease in low-frequency waves. The opposite pattern was observed during the least funny scenes. This suggests that high-frequency brain activity, which is associated with tasks that require a lot of thinking, is also involved in appreciating humor. On the other hand, scenes that are not funny promote inattention and introspection, leading to more low-frequency activity.
“In our study, we found that humor appreciation is achieved by an increased neural activity activity in high frequencies and decreased activity in low frequencies,” Axelrod told PsyPost. “This result could not be obtained in a study using functional MRI (fMRI) because the fMRI does not have sufficient temporal resolution.”
The findings support the idea that humor processing involves two complementary mechanisms: the detection of incongruity and the experience of positive emotions. The cognitive system responsible for detecting incongruity involves the temporal lobe, inferior frontal gyrus, and dorsal anterior cingulate cortex, while the emotional system involves brain areas like the insula, ventral anterior cingulate cortex, and mesocorticolimbic regions.
“Our results support this theory, as we confirm the prominent role of the temporal lobe in the appreciation of humor. 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,” said Axelrod. “Conversely, the activation of its posterior parts could correspond to understanding the unusual—and therefore amusing—aspect of certain social interactions.”
The study provides insights into the neural correlates of humor processing and highlights the role of the temporal lobe in humor. But the study authors said that further research is needed to explore the specific functions of these brain regions and to replicate and extend these findings using other techniques.
“Our study focused only on the temporal lobe,” Axelrod said. “In the future, it would be interesting to conduct an investigation using intracranial methodology in the additional brain regions.”
The study, “Intracranial study in humans: Neural spectral changes during watching comedy movie of Charlie Chaplin“, was authored by Vadim Axelrod, Camille Rozier, Elisa Sohier, Katia Lehongre, Claude Adam, Virginie Lambrecq, Vincent Navarro, and Lionel Naccache.