Tuesday, January 21, 2014

Why We Need Sleep

According to the Washington Post recent research has confirmed some theories about why human beings, and other animals, require sleep. During sleep the brain is bathed in cerebrospinal fluid that removes waste products and other toxins that accumulate during waking hours.

Staying up all night, the article says, could prevent the brain from getting rid of these toxins efficiently, and this would explain why sleep deprivation results in mental fog, crankiness, and increased risks of migraine and seizure.

Here's part of the WaPo's story:
Last year, [University of Rochester neurosurgeon] Maiken Nedergaard and her colleagues discovered a network that drains waste from the brain, which they dubbed the glymphatic system. It works by circulating cerebrospinal fluid throughout the brain tissue and flushing any resulting waste into the bloodstream, which then carries it to the liver for detoxification.

She then became curious about how the glymphatic system behaves during the sleep-wake cycle.

An imaging technique called two-photon microscopy enabled the scientists to watch the movement of cerebrospinal fluid through a live mouse brain in real time. After soothing the creature until it was sound asleep, study author Lulu Xie tagged the fluid with a special fluorescent dye.

“During sleep, the cerebrospinal fluid flushed through the brain very quickly and broadly,” said Rochester neuropharmacologist Xie. As another experiment revealed, sleep causes the space between cells to increase by 60 percent, allowing the flow to increase.

Xie then gently touched the mouse’s tail until it woke up from its nap, and she again injected it with dye. This time, with the mouse awake, flow in the brain was greatly constrained.

“Brain cells shrink when we sleep, allowing fluid to enter and flush out the brain,” Nedergaard said. “It’s like opening and closing a faucet.”

They also found that the harmful beta-amyloid protein clears out of the brain twice as fast in a sleeping rodent as in an up-and-about one. The study was published in the journal Science on Thursday.

New York University cell biologist and Alzheimer’s specialist Ralph A. Nixon, who was not involved in the study, said the findings could be of great interest to the Alzheimer’s research community. For instance, the overproduction of beta-amyloid could be linked to the development of the disease, but he said these new findings hint that the lack of clearing it out might be the bigger problem.

Other neurodegenerative disorders, such as Parkinson’s disease or chronic traumatic encephalopathy, are also associated with a backup of too much cell waste in the brain. “Clearance mechanisms may be very relevant to keeping these proteins at a level that isn’t disease-causing,” Nixon said.
There's more on this at the link.

So, if you're a college student who likes to stay up late and has to get up early and you wonder why you can't stay awake in class, it's because your brain is polluted with toxins and you may be on your way to Alzheimer's. Turn off the computer and get some sleep.