FIGURE 1.

Experimental protocol. Upper panel: participants were maintained in dim light after admission (1.5 h after their habitual waketime). They completed two fMRI sessions under light exposure in a counterbalanced order (blue light 480 nm, 3 × 10ˆ13 ph/cm/s² – orange light 620 nm, 3 × 10ˆ13 ph/cm/s²). The total duration of each session was 40 min during which participants performed an auditory n-back task. Upon arrival (baseline) and after each fMRI session, the pupils were measured. Pupils were dilated before, and right after, the first fMRI session (e.g., before second fMRI session). Subjective sleepiness and anxiety levels were also collected. Participants were exposed for 5 min to a bright polychromatic white light (1000 lux) before each fMRI session. Lower panels: within an fMRI session (i.e., including either blue or orange light), light was administered in block of 30 s and coincided with the 30 s task blocks (either 0b or 2b) or were administered alone. All blocks were separated by at least 15 s in complete darkness without task, which was either followed by a 30 s light exposure or a 30 s period in darkness. A total of 48 blocks of auditory 0b task (n = 18), 2b task (n = 20), and rest under light exposure (n = 10) were performed in each fMRI session. Half of n-back task blocks were executed under light exposure and the other half in darkness.