For a long time, sleep’s apparent uselessness amused even the scientists who studied it. The Harvard sleep researcher Robert Stickgold has recalled his former collaborator J. Allan Hobson joking that the only known function of sleep was to cure sleepiness. In a 2006 review of the explanations researchers had proposed for sleep, Marcos Frank, a neuroscientist then working at the University of Pennsylvania (he is now at WSU Spokane) concluded that the evidence for sleep’s putative effects on cognition was “weak or equivocal.”
But in the past decade, and even the past year, the mystery has seemed to be abating. In a series of conversations with sleep scientists this May, I was offered a glimpse of converging lines of inquiry that are shedding light on why such a significant part of our lives is spent lying inert, with our eyes closed, not doing anything that seems particularly meaningful or relevant to, well, anything.