Figure 1.

Actogram from a single animal showing disrupted rhythmicity in locomotor activity during chronic photoperiodic phase advance (a). Rolling seven-day average (mean ± SD) of the circadian rhythmicity parameters, inter-daily stability (IS) and intra-daily variability for all animals (IV) (b). The IS decreased from baseline after the PD intervention, indicating disrupted stability of rhythmicity between days. The IV increase from baseline following the PD, which indicates increased fragmentation of the daily circadian rhythm in locomotor activity. Mean rhythmicity indices (IS and IV) calculated over the duration of the baseline and PD periods for all animals, indicated significant changes in both parameters (c) (p < 0.0001, Student unpaired t test).