Suggestion of sleepiness

Sometimes, television shows will have scenes in which an actor plays the role of a patient about to undergo an operation. Occasionally, the patient is asked to start counting backward while the mask is applied over his nose and mouth to supply an anesthetic gas and send him to sleep.

“Despite more than 160 years of continuous use in humans, we still do not understand how anesthetic drugs work to produce the state of general anesthesia,” said University of Pennsylvania researcher Max Kelz in a statement. Anesthesiologist  Kelz and his colleagues tried to pin down the pathways in the brain that are involved in making anesthetics effective, reporting their findings in the Oct. 25 issue of the journal Current Biology.

“We showed that a commonly used inhaled anesthetic drug directly causes sleep-promoting neurons to fire,” he said. “We believe that this result is not simply a coincidence. Rather, our view is that many general anesthetics work to cause unconsciousness in part by recruiting the brain’s natural sleep circuitry, which initiates our nightly journey into unconsciousness.”

Work in two ways

Studying the effects of a commonly used anesthetic on the brains of mice, Kelz and his team found that anesthetics seem to work in two ways. One message that the brain receives is to stop staying awake and conscious, the researchers said. The other message activates the part of the brain that is involved in promoting and maintaining a sleep state in people, letting it go to work while the patient is unconscious.

If you’ve caught yourself yawning, or caught others yawning as they watch the patient on the TV show yawn and ultimately lose consciousness. That’s a phenomenon known as “contagious yawning.”

Some studies suggest that yawning when others do is a way to demonstrate empathy or a sense of connection with them. For example, chimpanzees, which form social groups, have been shown to demonstrate contagious yawning in the presence of other chimps from their own group. On the other hand, very young children or those who have disorders that can make social interactions challenging do not yawn in response when someone else does.

Grasp visual, vocal cues

Dogs are social animals as well, and one study released earlier this year indicates that, like infants, they can grasp visual and vocal cues that indicate when people are trying to get their attention. Other studies have shown that while dogs have also demonstrated contagious yawning, they did it regardless of whether or not the first yawn was from someone familiar or a complete stranger. Based on these findings, Swedish researchers from the University of Lund wondered about whether or not puppies demonstrated contagious yawning.

Working with nearly three dozen puppies aged 4 to 14 months, the team checked to see if contagious yawning was a behavior developed over time, just as children pick up social behavior cues from the adults around them. They found that “dogs are subject to a developmental increase in susceptibility to yawn contagion, as dogs above the age of 7 months yawned contagiously, while dogs between 4 and 7 months showed little evidence of contagion.”

The team’s results appeared in a study published online Oct. 18 in the journal Animal Cognition.

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