Use of Environmental Light Cycles to Distinguish Circadian Regulation from Direct Light Modulation of Learning and Mood

Previous work has suggested that circadian rhythms regulate cognitive functions and mood in human and mice. However, previous experiments housed mice in regular daily light: dark cycles preventing the dissociation of light from circadian rhythms. In light of recent findings in human, that light directly modulates attention and mood, we wanted to create light cycles which would allow the dissociation of light from circadian rhythms. Here we describe two light cycles, the first allows the measurement of behaviors in the absence of “white” light, and the second prevents mice from photoentraining but does not cause sleep disruption or circadian arrhythmicity. These cycles have allowed us to determine the circadian and light effects on learning and mood.