Human phase response curve to a 1 h pulse of bright white light

Exposure to 1 hour of bright white light induced a phase resetting response with a fitted peak-to-trough amplitude of 2.20 hours.

• The phase resetting response of the human circadian pacemaker is influenced by the timing of light exposure.
• A significant difference in phase response curves (PRCs) was found between the bright white light and dim background light conditions.
• No discernible PRC was observed for the <3 lux dim background light.
• The peak-to-trough amplitude of the 1 h bright white light PRC was approximately 40% of that observed in a previous 6.7 h bright white light PRC.
• This finding supports a non-linear relationship between light exposure duration and its effects on circadian resetting.

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