~ What happens while we sleep ~

As humans spend one-third of their lives sleeping, none of us curious to know what happens while we sleep. Most of us follow the normal routine; as night approaches we go to bed to get our daily dose of rest, so that we can start our next day afresh. 

Maiken Nedergaard, a Danish biologist and Sigrid Veasey, Associate Professor of Medicine at University of Pennsylvania’s Center for Sleep and Circadian Neurobiology have some interesting insights into the sleep function, the nocturnal cycle of the body mechanism & highlights the effects of lack of sleep. 

Here are some excerpts from Maria Konnikova's  post in NYT "Goodnight. Sleep Clean."

In a series of new studies, published this fall in the journal Science, the Nedergaard lab may at last be shedding light on just what it is that would be important enough. Sleep, it turns out, may play a crucial role in our brain’s physiological maintenance. As your body sleeps, your brain is quite actively playing the part of mental janitor: It’s clearing out all of the junk that has accumulated as a result of your daily thinking.

The lymphatic system serves as the body’s custodian: Whenever waste is formed, it sweeps it clean. The brain, however, is outside its reach — despite the fact that your brain uses up about 20 percent of your body’s energy. How, then, does its waste — like beta-amyloid, a protein associated with Alzheimer’s disease — get cleared? What happens to all the wrappers and leftovers that litter the room after any mental workout?

MODERN society is increasingly ill equipped to provide our brains with the requisite cleaning time. The figures are stark. Some 80 percent of working adults suffer to some extent from sleep deprivation. According to the National Sleep Foundation, adults should sleep seven to nine hours. On average, we’re getting one to two hours less sleep a night than we did 50 to 100 years ago and 38 minutes less on weeknights than we did as little as 10 years ago. Between 50 and 70 million people in the United States suffer from some form of chronic sleep disorder. When our sleep is disturbed, whatever the cause, our cleaning system breaks down. At the University of Pennsylvania’s Center for Sleep and Circadian Neurobiology, Sigrid Veasey has been focusing on precisely how restless nights disturb the brain’s normal metabolism. What happens to our cognitive function when the trash piles up?

There is, however, reason to hope. If the main function of sleep is to take out our neural trash, that insight could eventually enable a new understanding of both neurodegenerative diseases and regular, age-related cognitive decline. By developing a diagnostic test to measure how well the glymphatic system functions, we could move one step closer to predicting someone’s risk of developing conditions like Alzheimer’s or other forms of dementia: The faster the fluids clear the decks, the more effectively the brain’s metabolism is functioning.