Fig. 3:

T-cycles. T-cycles are LD cycles with a period length other than 24 hours (T = L + D). Mice are able to entrain to T-cycles of 23 (B) and 25 (D) hours but not to T-cycles of 22 (A) and of 26 (E) hours. Panel C represents a normal 24 hours LD 12:12 cycle. All schemes are plotted on 24 hours scale where the white area represents lights on and the gray area lights off, respectively. The white and black bar at the top of the scheme depicts light and darkness of the LD 12:12 cycle the animals were entrained to in the beginning of each panel. Each species has a distinct range of entrainment; the schemes here represent the range for mice. The black horizontal bars display the active time of the animals. LD, light–dark cycle; T, period or cycle time of a Zeitgeber; h, hours.