Short-Wavelength Countermeasure for Circadian Desynchrony

Exposure to light at critical phases of the circadian cycle is the main stimulus that phase shifts and entrains circadian rhythms. Whereas previous work has concluded that exposure of humans to bright light for an hour or more at the right phase of the circadian cycle produces significant phase shifts of circadian rhythms, and can speed recovery from jet-lag thus facilitating restorative sleep. Our work on mice has produced the unexpected result that exposure of the animals to intermittent millisecond flashes of light distributed over an hour for a total of only 120 msec. of light can produce maximum phase shifts. We have also shown that the effects of light on the circadian system of mice is mediated through a unique photopigment - melanopsin, and the properties of this system explain the effectiveness of brief flashes of light as entraining signals. We propose a proof of concept study to demonstrate whether or not millisecond flashes of light can phase shift the human circadian system. On the basis of these results, we will develop a phase shifting device for military and commercial applications.