Figure 1.

Design and procedures. Each participant performed on a Sleep and a Wake condition separated by at least 3 weeks. Conditions started with encoding of 256 MST items followed by an immediate recognition test (192 items), followed by a 9 h retention interval covering nocturnal sleep (Sleep condition) or daytime wakefulness (Wake condition). Thereafter, delayed recall (192 items not used for immediate recall) was tested. Displayed pictures in the graph are taken from the original image database of the MST. ISI, Interstimulus interval.