Secrets of the sleep-deprived brain

If you find it hard to focus after a wakeful night, it's because your brain is busy trying to catch up on crucial housekeeping. Nearly everyone has experienced it--after a night of poor sleep, your brain might seem foggy, and your mind drifts off when you should be paying attention. A new MIT study reveals what happens biologically as these momentary lapses occur: Your brain is performing essential maintenance that it usually takes care of while you sleep. During a normal night of sleep, the cerebrospinal fluid (CSF) that cushions the brain helps flush away metabolic waste that has built up during the day. In a 2019 study, MIT electrical engineering and computer science professor Laura Lewis, PhD '14, and colleagues showed that the CSF flows rhythmically in and out in a way that's linked to changes in brain waves. To explore what might happen to this CSF flow in a sleep-deprived brain, Lewis, who is also a member of MIT's Institute for Medical Engineering and Science, and her colleagues tested 26 volunteers on several cognitive tasks after they'd been kept awake in the lab and when they were well-rested.