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Time course of pupil measures during 29 h of sustained wakefulness (mean ± sem). (A) Steady-state pupil size (mm2) significantly varied with circadian phase. (B) Pupil size variability (mm2 s−1) did not yield significant variation with circadian phase. Refer to main text for outputs of statistical tests. Average melatonin profile is displayed in grey. Time course is expressed relative to individual dim light melatonin onset (DLMO = phase 0°; 15° = 1 h).
