Laughter And The Brain

Modern neurophysiology states that laughter is linked with the activation of the ventromedial prefrontal cortex, which produces endorphins after a rewarding activity: after you have a good meal, after you have sexual intercourse and after you understand a joke. Research has shown that parts of the limbic system are involved in laughter. The limbic system is a primitive part of the brain that is involved in emotions and helps us with basic functions necessary for survival. Two structures in the limbic system are involved in producing laughter: the amygdala and the hippocampus[citation needed].

The December 7, 1984 Journal of the American Medical Association describes the neurological causes of laughter as follows:

"Although there is no known 'laugh centre' in the brain, its neural mechanism has been the subject of much, albeit inconclusive, speculation. It is evident that its expression depends on neural paths arising in close association with the telencephalic and diencephalic centres concerned with respiration. Wilson considered the mechanism to be in the region of the mesial thalamus, hypothalamus, and subthalamus. Kelly and co-workers, in turn, postulated that the tegmentum near the periaqueductal grey contains the integrating mechanism for emotional expression. Thus, supranuclear pathways, including those from the limbic system that Papez hypothesised to mediate emotional expressions such as laughter, probably come into synaptic relation in the reticular core of the brain stem. So while purely emotional responses such as laughter are mediated by subcortical structures, especially the hypothalamus, and are stereotyped, the cerebral cortex can modulate or suppress them."

Where Does Laughter Come From?

By Bob Beale, ABC Science Online
http://dsc.discovery.com/news/afp/20031006/laughter.html

Oct. 7, 2003 — The special sounds and gestures made by infant bonobos also known as pygmy chimpanzees when they are tickled suggest that the origins of laughter may pre-date human evolution, according to a new report.

A study of a young bonobo in a German zoo found that when it was tickled it combined vocalizations and facial gestures much like those made by human infants, said the report in the BioMednet science news service.

The finding suggests that the rules for how emotion is encoded behaviorally were laid down in the common ancestor humans shared with other great apes, Elke Zimmermann of the Institute of Zoology at the Tieraerztliche Hochschule, in Hanover, told a recent conference of the German Primate Society.

The sounds made by the bonobo when tickled during its first year of life were carefully recorded at Wuppertal Zoo eight years ago by another researcher, Birgit Förderreuther, who was unable to continue the study due to illness, the report said.

Now Zimmerman has conducted a sophisticated analysis of the recordings and compared them with sounds made by human babies when they are tickled.

She found that the bonobo's vocalizations followed broadly the same spectrographic pattern — a technique that depicts the changes in frequency and intensity of the sound over time — as that of human infants, except that the bonobo's laugh was at higher frequencies.

Infant bonobos and humans both combine those sounds with a facial gesture known as a "relaxed open-mouth display."

Zimmerman believes that her findings confirm a hypothesis that laughter originated in primates, as a universal signal of wellbeing in a playful situation to help regulate social interactions, the report said.

"A pre-human evolutionary origin for laughter could also explain why it is still present in deaf and blind infants, and why it fulfils the same role — and sounds the same — in people from different cultures," it said.

Laughter is well documented in common chimpanzees, with observations of both wild and captive chimpanzees revealing that they even share with humans the same ticklish anatomical regions — the armpits and belly.

Chimpanzee laughter, however, involves a more rapid panting action with sound made on both inhalation and exhalation of air. Human laughter tends to involve sound made mainly on exhalation.

Chimpanzees are also known to continue enjoying tickling well into adulthood. Among young chimpanzees that have been taught sign language, tickling is a frequent topic of conversation, according to a recent article on the biology of laughter in Discover magazine.

But chimpanzee laughter usually happens in a different social context than it does in humans: chimps laugh almost exclusively during physical contact, or when contact is imminent during chasing and wrestling games, whereas most adult human laughter occurs during conversation without touching being involved, according to Robert Provine, a psychologist at the University of Maryland, who is an authority on laughter.

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