Fig. 1.

Clock mutant mice are hyperactive. Rearing behavior (a) and locomotor activity (b) were measured in a novel environment over 2 hours with the number of beam breaks measured every 15 min. (c and d) Activity throughout the light/dark cycle was measured for 24 h, with activity recorded every 30 min. The solid dark bars indicate the dark cycle. All data points are significant (a and b) (P < 0.05 by ANOVA, n = 6). The total activity over 24 h is also significantly different for both rears and ambulations (P < 0.05 by ANOVA, n = 6). Clk, Clock mutants; WT, wild-type mice.