Why Do We Sleep? Scientists Say To Forget


During the day we constantly process new information, thoughts, ideas, and sensory data. By nighttime, it’s no wonder our bodies crave rest. A pair of studies suggests that sleep helps us recalibrate and enhance learning by allowing the brain to forget some of what it learns during the day.

The studies from the University of Wisconsin and Johns Hopkins University offer evidence that the function of sleep is to allow our brains to “sift through the junk,” by weakening the connections – or neural networks – that hold our memories together. This allows some memories to grow and stick, and others to be discarded.

The studies, published this month in the journal Science, explain that during sleep the brain recalibrates the neural networks by strengthening the connections it needs most and forgetting the others.

“Sleep is a time for our bodies, including the brain, to refresh and rejuvenate,” says Suleman Iqbal, MD, a Sleep Medicine and Internal Medicine physician at the McKay-Dee Sleep Center. “When the body is deprived of sleep, it’s harder to learn and recall information, particularly for the formation of long-term memories."

“It is during deep sleep and REM sleep that memories are sewn into the brain,” he says. “Infants are in REM sleep approximately 90 percent of the time because everything they learn is new and the brain needs that time to integrate the memories. By the time you reach age 90, the amount of REM sleep is significantly reduced because most of those connections are already made.”

How can you sleep better to support your brain?

  • Follow a good sleep schedule. “The most important thing regarding sleep is to establish a regular bedtime routine and aspire to go to bed and wake up the same time 7 days a week," says Dr. Iqbal. “There’s a reason why our grandparents eat dinner at the same time every night and are consistent with their bedtime and wake up time.”
  • If you wake up in the night, find out why. “It’s hard to get into a deep sleep when you have a lot on your mind,” he says. “For some people the stress and anxiety needs to be addressed. For others, there might be an intrinsic sleep disorder (such as obstructive sleep apnea), a hormone imbalance (particularly in women going through menopause), or medication side effect causing the problem. Talking to a sleep specialist can help you learn why your sleep is unstable.”
  • Cut technology out at least an hour before bed. The light from artificial light sources, like smart phones, fools your brain into thinking it’s sunrise. Instead, look for things you find relaxing, like meditating or reading a book. 

I tell my patients that sleep is like money, adds Dr. Iqbal. “If you accumulate a sleep debt, you’re going to have to pay it back at some point.” Plus, your brain and your memories will thank you.