A recent study revealed that laughter is not merely a response to amusement, but a complex neurological phenomenon controlled by two different systems in the brain: one responsible for spontaneous, involuntary laughter, and the other for laughter associated with social interaction and conversation.
The study, published in the journal Trends in Neurosciences, explained that laughter is often a social behavior, as it is more likely to occur in the presence of others, and it contributes to strengthening social bonds, expressing understanding and agreement, and relieving stress.
Interactive laughter, which we use while talking to others, differs from spontaneous, uncontrollable laughter. The former is usually short and low-pitched, while the latter lasts longer, is louder, and may be accompanied by a feeling of pleasure and happiness.
To understand the neural mechanisms behind this phenomenon, researchers reviewed studies that examined the stimulation of different regions of the brain, including research conducted in collaboration with the epilepsy surgery unit at Niguarda Hospital in Milan, Italy.
Two different networks for laughter
The researchers concluded that there are two distinct brain networks:
- The first network: Spontaneous laughter. It includes the anterior cingulate cortex, the temporal pole, and subcortical regions; its activation leads to involuntary laughter that may be accompanied by a feeling of happiness and pleasure. This network is linked to evolutionarily ancient neural systems shared by mammals for producing emotional sounds and expressing playfulness.
- The second network: Voluntary laughter. It is linked to the motor and premotor areas of the brain and helps produce the laughter used during conversations and social interactions, without necessarily being an expression of a genuine feeling of amusement.
What is the relationship between laughter and speech?
The results indicate that voluntary laughter relies on motor control mechanisms associated with speech, making it more neurologically complex. As for spontaneous laughter, it relies on older neural circuits associated with automatic emotional expression.
These differences help explain certain neurological conditions; a person who has suffered a stroke may lose the ability to speak or control voluntary laughter, while their ability to laugh spontaneously, cry, or scream remains preserved if the networks responsible for these responses remain intact.
The researchers believe that understanding these networks may contribute to clarifying the relationship between emotions, social communication, and motor control, and also paves the way for deeper studies on how laughter originates within the brain.
