Figure 1. Experimental protocol. a, Left, On day 1 (encoding phase), subjects saw a series of words, one at a time. They were instructed to read mentally the word presented. Each word was followed by the instruction “To remember” or “To forget.” b, After the session, they were either allowed regular sleep (RS group) or were totally sleep deprived (TSD group) for the first postlearning night. Subjects were all retested after two recovery nights using a recognition task (a, right), during which they had to determine, for each word presented, whether they had previously seen it or not, regardless the instruction given at learning. fMRI data were acquired during both encoding and recognition.