Participants were instructed not to drink coffee, tea, or any other beverage containing stimulants and to refrain from smoking cigarettes in the 2 h before the beginning of the recording session. Information on the quality of sleep during the night prior to the recording was collected and the EEG session was postponed if the subject reported a non-restoring sleep. Women were recorded during the follicular phase of menstrual cycle. EEG was continuously recorded for 3 min while the subjects were at rest with closed eyes. Participants sat comfortably in an armchair, in a sound attenuated room and were instructed to relax while staying awake with eyes closed and to limit eye movements.
