Figure 1.

This protocol started with three baseline nights [B1–B3; 9 h time in bed (TIB)], followed by seven nights of sleep manipulation (M1–M7) with 9 h TIB for the control group and 5 h TIB for the sleep restriction (SR) group. Both groups had 9 h TIB during recovery nights (R1–R3). Encoding (study) took place on the evening of the third baseline night. Retrieval took place before and after the sleep manipulation period (test 1, test 2) and 6 weeks after encoding (test 3; not depicted). Asterisks indicate nights that participants’ sleep was monitored by polysomnography. Sleep–wake patterns were monitored continuously by actigraphy except during night B1, when all Actiwatches were charged.