Laughter does have the power to override other emotions momentarily – we cannot sob morosely or simmer with anger while simultaneously laughing. This is because our facial muscles and vocal architecture have been hijacked by sunnier emotions. And it is all controlled by specialized brain circuits and chemical messengers (neurotransmitters).
We know there are several brain pathways that contribute to laughter – each for different components of it. For example, brain regions usually involved in decision-making and controlling our behavior have to be inhibited to facilitate spontaneous and unbridled laughter. Laughter also relies on emotional circuitry connecting areas responsible for experiencing emotion with those required for expressing emotion.
What Illness Can Teach Us
While we have garnered detailed knowledge of brain features crucial for facial expressions, swallowing, tongue and throat movements, far less is known about how positive emotions actually get transformed into laughter. Luckily, a number of illnesses and conditions have helped shed some light on its underlying neural functions.
One particularly well documented syndrome, thought to be first identified by Charles Darwin, involves an unsettling exhibition of uncontrolled emotion. It is clinically characterized by frequent, involuntary and uncontrollable outbursts of laughing and crying. This is a distressing disorder of emotional expression at odds with the person’s underlying feelings. The condition is known as pseudobulbar affect syndrome and may be expressed in several