Ever wake up after a bad night’s sleep and feel like your brain just won’t focus? Turns out it might be cleaning itself. During deep non-REM sleep, cerebrospinal fluid rushes through the brain like a rinse cycle, clearing out metabolic waste. But when we don’t sleep well, the brain may try to squeeze in mini “cleaning cycles” while we’re awake, and that momentary slosh of fluid can cause attention lapses. A study found people performed worse on focus tasks after sleep deprivation, right when the