Figure 1.

Experimental protocol. Participants were maintained in dim light for 2 h before starting the fMRI protocol, 1 h after their habitual bedtime. Participants performed a total of 28 blocks of auditory two-back task divided across four conditions: darkness and exposure to blue monochromatic light (480 nm) of three different irradiance levels (low: 7 × 10¹² ph/cm²/s; medium: 3 × 10¹³ph/cm²/s; high: 10¹⁴ph/cm²/s). The order of the four conditions was counterbalanced within each group, except for high irradiance blue light that was never presented first. Task blocks lasted 45 sec separated by rest periods of 20 to 30 sec in darkness. Total duration of the fMRI session was about 30 min.