Figure 4.

Reentrainment of Per1 expression in the SCN to 6 h phase advance in the light cycle. a, Control phase plane. b, Phase plane on day 1 after 6 h advance in light schedule. The orientation of the phase plane formed by the tops of the histograms reveals that the lateral region of the SCN has shifted significantly more than the medial regions. c, On day 3 after the light schedule change, the phase relationships have not returned to normal, as indicated by the lack of a phase difference between the dorsomedial and ventrolateral regions. d, By 6 d after the advance in the light schedule, the regional phase differences have been restored. e, Per1-luc rhythms in dorsomedial and ventrolateral regions of the SCN before shift in light schedule (control). f-h, Per1-luc rhythms on days 1, 3, and 6 after light cycle advance. In e-h, error bars indicate SE. The conventions are the same as in Figure 3.