Restorative, restful sleep is well-known now as an extremely important part of being healthy, and it’s especially helpful for keeping athletes and fitness junkies performing their best during waking hours. It’s an important time for the body to repair tissue, build muscle, and do general housekeeping.

But a new study from the University of Zurich and the Swiss Federal Institute of Technology has found that deep sleep is responsible for making the brain much more efficient at learning. Researchers had six women and seven men learn three different motor tasks using their fingers during the day, and then monitored their brain waves at night. On the first night, the scientists left the subjects’ brains alone, but on the second night, they used sounds to stimulate parts of the brain used in motor skill-control during the deep sleep portion.

Then during the day (after the sleep manipulation and deep sleep), they retested the subjects’ motor skills learning tasks. The researchers observed that after normal sleep the participants would have no trouble learning the skills in the morning, but then would make more mistakes near the end of the day. A night of deep sleep erased those missteps for the morning on the next day. But for those days when the subjects’ brains were bounced out of deep sleep by the sounds, they showed significant difficulty in learning the finger movements.

“In the strongly excited region of the brain, learning efficiency was saturated and could no longer be changed, which inhibited the learning of motor skills,” said study co-author Nicole Wenderoth, Ph.D., a professor in the department of health sciences and technology at the Swiss Federal Institute of Technology.

To make sure you make it into deep sleep every night, limit alcohol and caffeine at least six hours before bed, turn off digital devices and limit screen time a few hours before lying down to sleep, and make sure your bedroom is cool, dark, and quiet.