Fig. 4.

Representative actograms following single-day 6-hr dark pulses late during the day or single-day 6-hr light pulses late at night. Mice subjected to single-day 6-hr advances of the light-dark cycle experience 6 hrs of darkness late in their day and 6 hrs of light late at night. (A) Exposure to only the 6-hr dark pulse in the latter half of the light period yields no noteworthy change in phase of activity rhythms. (B) Exposure to only the 6-hr light pulse at night yields large phase advances in BALB/cJ but not C57BL/6J mice. Shaded areas correspond to lights off. (*, p<.05)