Figure 2.

Timeline detailing the study procedure. Between 09:45 and 10:15, participants underwent 30 minutes of “washout” amber light exposure. Immediately following the washout period, participants either received 30 minutes of amber placebo light or blue light exposure (i.e., between 10:15 and 10:45). During this time, at 10:20, participants received instructions on the N-back task and completed one practice run, lasting 10 minutes in total. At 11:00, participants began the fMRI scan, and the N-back task was initiated at 11:25 and ended at 11:33. The scan ended at 12:30. Participants completed the Stanford Sleepiness Scale (SSS) 3 times during the procedure, including just before the start of the washout period, immediately after the light exposure, and at 12:45 after exiting the fMRI scanner.