What happens in your brain when you can't stop laughing?
Do you remember the last time you were laughing and simply could not stop? Perhaps it was a situation when you should not have been laughing at all.
Laughter is often associated with amusement, but it primarily serves social purposes. People are 30 times more likely to laugh when with others than alone, and laughter during conversations can occur through contagion—catching the laughter from others. This laughter, often called voluntary, serves to demonstrate agreement, understanding, and cement friendships.
It typically lasts short, has a lower pitch, and starts and stops quickly. On the other hand, helpless laughter, which is involuntary and incapacitating, involves strange squeaks and whistles.
The origins of these two types of laughter may lie in distinct brain systems. When studying the brain networks behind laughter production, researchers faced challenges due to the movement involved in laughter and difficulty obtaining natural laughter in laboratory conditions. Additionally, several brain regions are connected to laughter.
In the epilepsy surgery unit at Niguarda Hospital in Milan, patients with drug-resistant epilepsy undergo electrical brain stimulation, which can trigger laughter in these patients. This stimulation reveals two separate laughter networks.
One network, involving the anterior cingulate cortex, the temporal pole, and subcortical regions, triggers laughter accompanied by pleasant sensations and happiness. This network maps onto a vocalizing network shared by humans and other mammals, potentially responsible for other spontaneous emotional vocalizations like crying. This network activates a neurochemical cascade involving the opioid system, resulting in pleasure and reward.
The serotonin system, which regulates pain sensitivity, is also affected, potentially explaining why this laughter can temporarily dull physical pain. This network is ancient and common to both humans and animals, associated with spontaneous emotional responses and rough-and-tumble play systems.
The second network, consisting of brain areas in the motor and premotor regions, leads to speech impairments when stimulated and is not associated with any emotional state. This network is primarily responsible for voluntary laughter and is linked to complex vocal acts such as speaking, singing, and beatboxing. Research shows that vocal tract shapes during conversational laughter resemble those used in speech, while involuntary laughter has simpler motor control and a different appearance.
This research suggests that voluntary laughter requires more complex and refined motor control than spontaneous laughter, occupying a middle ground between spontaneous laughter and spoken language, both functionally and anatomically.
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