Laughter is not always triggered by something funny. Sometimes a person starts laughing at the worst possible moment and cannot stop, even when the situation calls for the opposite, reports infohub.kz.

Neuroscientists analyzed studies in which electrical stimulation of various brain regions triggered laughter in patients and identified distinct mechanisms underlying the phenomenon. The work was published in the journal Trends in Neurosciences.

Two types of laughter

We often laugh for social reasons — to support someone, express agreement or ease tension. Laughter is also contagious: the sound of someone else's laughter can trigger a similar response. Social laughter is usually short and lower in pitch. It differs from involuntary laughter, which often lasts longer, sounds higher and may be accompanied by unusual overtones.

Which brain regions are responsible for laughter

It turned out that electrical stimulation of different brain areas can trigger laughter, but the sensations differ. When a network including the anterior cingulate cortex, the temporal pole and certain subcortical structures was stimulated, patients experienced pleasant sensations and a feeling of joy. This system is thought to be involved in spontaneous, hard-to-control laughter. Another network is located in the motor and premotor areas of the brain, which are involved in controlling movement. Stimulating it also triggered laughter, but without any particular emotional experience.

Why involuntary laughter feels good

The first neural network is linked to the system of vocal responses. It is involved in spontaneous emotional sounds, such as screaming. Activation of this system sets off a chain of neurochemical reactions involving, in particular, the brain's opioid system. This may explain the feeling of pleasure that accompanies uncontrollable laughter. The serotonin system, which helps regulate pain sensitivity, also changes its activity. This may explain the temporary reduction in pain during such laughter. From an evolutionary standpoint, this system is more ancient. It has been linked to play behavior in animals, and its mechanisms have survived in many mammals to this day.

Laughter has another unexpected benefit — in one study, laughter therapy proved effective against the symptoms of lung diseases.