Without sleep, your brain doesn't work as well storing memories or doing nightly housecleaning

ight owls, take note. That sleep deficit you've been accumulating has real and dangerous implications for your brain, and not just because it makes you sleepy during the day. Sleeping less than seven or eight hours a night has been linked to memory loss and cognitive decline, new research shows.
 
P. Murali Doraiswamy, M.D., a brain researcher at Duke University in Durham, N.C., explains what your brain does during sleep.

Clears out toxins

Most people think that when you sleep, your brain goes to sleep, too. But it turns out that parts of your brain are several times more active at night than during the daytime. One of them is a newly discovered drainage system called the glymphatic system, which is kind of like your city's sewage and recycling system. Its job is to clear out and recycle all your brain's toxins. One protein very actively recycled during sleep is involved in developing amyloid plaque, the hallmark of Alzheimer's. No one is saying that Alzheimer's is all caused by sleep deprivation, but it may be a factor.

Repairs daily wear and tear

New research indicates chronic sleep deprivation can lead to irreversible brain damage. A University of Pennsylvania animal study found that extended wakefulness can injure neurons essential for alertness and cognition - and that the damage might be permanent. Short sleep also may be linked to shrinking brain volume, though it's not clear whether the lack of sleep causes the brain to shrink or whether a smaller brain makes it harder to sleep. Other studies have led scientists to conclude that chemicals secreted during the deeper stages of sleep are crucial for repairing the body – including the brain.

Makes order from chaos

As you go about your daily activities, your brain is exposed to thousands of stimuli - auditory, visual, neurosensory. And it can't possibly process all that information as it comes in. A lot of the tagging and archiving of memories occurs at night while you're sleeping. It's a bit like what goes on in a library. All the books dropped off in the book repository during the day are dusted off and cataloged at night. People who think they've adapted well to sleeping just four or five hours a night are often wrong; memory tests show they are not functioning optimally.