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Why Do We Sleep?

In order to dream, we first have to sleep. Humans spend about one-third of their lives asleep, but sleep researchers still don't know why we do it.

The function of sleep is one of the 125 greatest unsolved mysteries in science. Theories range from brain "maintenance" to reversing damage from stress suffered while awake, to promoting longevity. None of these theories are well established, and some of them contradict each other.

Psychiatrist Jerome Siegel says, "Sleep has normally been viewed as something negative for survival because sleeping animals may be vulnerable to predation (being eaten) and they can't perform the behaviors that ensure survival." These behaviors include eating, procreating, caring for family members, monitoring the environment for danger and scouting for prey. "So it's been thought that sleep must serve some as-yet unidentified physiological or neural function that can't be accomplished when animals are awake."

Siegel conducted a survey of the sleep times of a broad range of animals, from the platypus and the walrus to the echidna, a small, burrowing, egg-laying mammal covered in spines. He concluded that there are inactive states in a wide range of species, starting with plants and simple microorganisms. This challenges the idea that sleep is for the brain, since some of animals have very small ones.

He says, "We see sleep as lying on a continuum that ranges from these dormant states like torpor and hibernation, on to periods of continuous activity without any sleep, such as during migration, where birds can fly for days on end without stopping." Hibernation is one example of an activity that regulates behavior for survival. A small animal, Siegel noted, can't migrate to a warmer climate in winter. So it hibernates, effectively cutting its energy consumption and thus its need for food, remaining secure from predators by burrowing underground. Many animals seem to sleep deeply but can become instantly awake when necessary.

Humans can do this too. Siegel says, "The often cited example is that of a parent arousing at a baby's whimper but sleeping through a thunderstorm. That dramatizes the ability of the sleeping human brain to continuously process sensory signals and trigger complete awakening to significant stimuli within a few hundred milliseconds."

In order to have a good sleep, all we need is a great interview to listen to, a gorgeous desert location and a nice fall evening under the stars. Join us: We promise no nightmares will occur!

Art credit: Dreamstime.com

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