Figure 1

Within-subject, randomized, cross-over study design. Circadian alignment (upper panel) and misalignment (lower panel) protocols. For the former, scheduled sleep times were maintained between 11PM to 7AM across all days, while for the latter these timings were inverted by 12 h after Day 1. During Day 2 for the aligned condition, the Psychomotor Vigilance Task (PVT) and Probed Recall Memory (PRM) with Presentation phase (PP) and Recall phase (RP) were conducted at 2PM and 6PM, the Addition Task (ADD) at 12PM and 4PM, and the Unstable Tracking Task (TKT), Digit Symbol Substitution Task (DSST), Performance evaluation and effort scales (PEERS) and Karolinska Sleepiness Scale (KSS) at 12PM, 2PM, 4PM and 6PM. For the misaligned protocol, timing of cognitive testing during Day 2 was inverted by 12 h. Light levels were 90 lux to simulate typical room light intensity, 450 lux for 30-minute periods to simulate the morning commute preceding the simulated day shift and following the simulated night shift, 4 lux to permit assessment of dim-light melatonin levels, and 0 lux during scheduled sleep.