During sleep, the mammalian CNS undergoes widespread, synchronized slow-wave activity (SWA) that directly varies with previous waking duration (Borbély, 1982; Dijk et al., 1990). When sleep is restricted, an enhanced SWA response follows in the next sleep period. The enhancement of SWA is associated with improved cognitive performance (Huber et al., 2004), but it is unclear either how the SWA i...