Fig 1.
Schematic representation of one session (wake or nap, bright light exposure or placebo) of the protocol.
Each pair of sessions was scheduled according to the participant’s sleep schedule and wake up time. An example of the timings is shown for a person waking up at 7:30am.
Fig 2.
For each trial, a fixation cross is followed by a cue, after which three figures are presented. Participants are asked to decide which of the 2 lower figures matches the top one, depending on the cue, and is required to press the corresponding key (left key for left figure and right key for right figure).
Fig 3.
Latency switch-cost score (reaction times, Fig 3A) and accuracy switch-cost score (correct responses, Fig 3B) are represented for both groups (nap/wake and bright light/placebo). ΔPL (ΔLA) indicates the difference of switch cost between the morning session and the post-lunch session (late afternoon session). Vertical bars represent SD. Bright light intervention resulted in a decreased latency switch-cost score post lunch (Fig 3A). In the control condition (wake/placebo), a post-lunch dip in task switching was evidenced by an increased accuracy switch-cost score. Both interventions (short nap/bright light) elicited a significant decrease of this post-lunch dip (Fig 3B).
Fig 4.
Significant correlations were obtained for the modulations (differences between intervention and control conditions) between A. the accuracy switch-cost score and the fatigue scores during the post-lunch session (Fig 4A, both groups), B. the accuracy switch-cost score and the variability in the Psychomotor Vigilance Task during the post-lunch session (Fig 4B, both groups), C. the accuracy switch-cost score post lunch and the amount of stage N1 (Fig 4C, nap group only) and D. the accuracy switch-cost score in the late afternoon and the amount of stage N1 (Fig 4D, nap group only).