Combination of Light and Melatonin Time Cues for Phase Advancing the Human Circadian Clock (original) (raw)

Phase Advancing with Bright Light and Melatonin-Burke et al INTRODUCTION The mammalian master circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. 1,2 The SCN provides environmental and biological timing information to the rest of the body so that physiology and behavior are coordinated for optimal functioning relative to the time of day. 3,4 The SCN receives input about environmental time through photic pathways via rod, cone, and melanopsin photoreceptors in the retina. 5,6 The SCN also receives input about behavioral and physiological states through non-photic pathways (e.g., serotonergic input from the raphe nucleus). 7-10 Misalignment between environmental time and internal biological timing (e.g., shift work, jet lag, circadian sleep-wakefulness disorders) can result in adverse psychological, neurobehavioral, and physiological consequences. 11-16 Photic and non-photic stimuli have both been used to phase shift the human circadian clock; however, there is limited information about how combinations of phase-shifting stimuli influence the timing of the circadian clock in humans. Findings from research in non-humans suggest the combination of photic and non-photic stimuli interact to increase or attenuate the magnitude of circadian phase shifts 17-21 and contribute to LIGHT AND MELATONIN FOR PHASE ADVANCING THE HUMAN CIRCADIAN CLOCK