(NEWSER) – Feeling a bit muddled after a sleepless night? It may be because your brain didn't get a chance to flush out built-up toxins, NPR reports. While we're asleep, the brain acts, in a researcher's words, "like a dishwasher"—at least in animals studied, including mice and baboons. Last year, the BBC notes, experts discovered a "plumbing" system in the brain. During sleep, it seems, it's working in overdrive, "pumping fluid into the brain and removing fluid from the brain in a very rapid pace," researcher Maiken Nedergaard says.