"Videorecording"@en . "Russell Foster is a circadian neuroscientist: He studies the sleep cycles of the brain. And he asks: What do we know about sleep? Not a lot, it turns out, for something we do with one-third of our lives. In this talk, Foster shares three popular theories about why we sleep, busts some myths about how much sleep we need at different ages - and hints at some bold new uses of sleep as a predictor of mental health."@en . "Why do we sleep?"@en . . "TEDTalks Russell Foster - Why do we sleep?"@en . "Internet videos"@en . . . . . "Educational films"@en . . . "Russell Foster"@en . "Films Media Group." . . . . "Films for the Humanities & Sciences (Firm)" . .