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"Why do we sleep? We spend a third of our lives doing so, and all known animals with a nervous system either sleep, or show some kind of related behaviour. But scientists still don't know what the point of it is. There are plenty of theories. Some researchers argue that sleep has no specific function, but rather serves as evolution's way of keeping us inactive, to save energy and keep us safely tucked away at those times of day when there's not much point being awake. On this view, sleep is like hibernation in bears, or even autumn leaf fall in trees. But others argue that sleep has a restorative function-something about animal biology means that we need sleep to survive. This seems like common sense. Going without sleep feels bad, after all, and prolonged sleep deprivation is used as a form of torture. We also know that in severe cases it can lead to mental disturbances, hallucinations and, in some laboratory animals, eventually death. Waking up after a good night's sleep, you feel restored, and many studies have shown the benefits of sleep for learning, memory, and cognition. Yet if sleep is beneficial, what is the mechanism? Recently, some neuroscientists have proposed that the function of sleep is to reorganize connections and "prune" synapses-the connections between brain cells. Last year, one group of researchers, led by Gordon Wang of Stanford University reviewed the evidence for this idea in a paper called Synaptic plasticity in sleep: learning, homeostasis and disease."

"Talking about ourselves-whether in a personal conversation or through social media sites like Facebook and Twitter-triggers the same sensation of pleasure in the brain as food or money, researchers reported Monday. About 40% of everyday speech is devoted to telling others about what we feel or think. Now, through five brain imaging and behavioral experiments, Harvard University neuroscientists have uncovered the reason: It feels so rewarding, at the level of brain cells and synapses, that we can't help sharing our thoughts. Bragging gives the same sensation of pleasure as food and money. The same areas of the brain are activated, scans show. "Self-disclosure is extra rewarding," said Harvard neuroscientist Diana Tamir, who conducted the experiments with Harvard colleague Jason Mitchell. Their findings were published in the Proceedings of the National Academy of Sciences. "People were even willing to forgo money in order to talk about themselves," Ms. Tamir said. To assess people's inclination for what the researchers call "self disclosure," they conducted laboratory tests to see whether people placed an unusually high value on the opportunity to share their thoughts and feelings. They also monitored brain activity among some volunteers to see what parts of the brain were most excited when people talked about themselves as opposed to other people. The dozens of volunteers were mostly Americans who lived near the university. In several tests, they offered the volunteers money if they chose to answer questions about other people, such as President Obama, rather than about themselves, paying out on a sliding scale of up to four cents. Questions involved casual matters such as whether someone enjoyed snowboarding or liked mushrooms on a pizza. Other queries involved personality traits, such as intelligence, curiosity or aggression."