Figure 1.

Schema for experiments 1 and 2. Timing of different phases for each experiment. In experiment 1, subjects arrived at the laboratory at 11:00 A.M. Following informed consent, participants performed the encoding portion of the word pair associates and virtual reality (VR) tasks, followed by setup of EEG electrodes. After a 2 h nap opportunity, participants completed the recall portions of the VR and word pair associates tasks, respectively. In experiment 2, participants arrived at the sleep laboratory at 9:00 P.M. for the accommodation night (no memory tasks or stimulation performed). On experimental nights (weeks 1 and 2), participants arrived at the sleep laboratory at 8:00 P.M. for EEG electrode setup, followed by word pair associates encoding at ∼9:00 P.M. Light’s out started at 11:00 P.M., and participants were awoken at ∼6:00 A.M. (e.g., after 7 h). A 1 week delay (washout) occurred between every session.