A) Average mRNA levels under both control (mean ZT1-6; ± 1SEM; n = 12/strain; grey) and SD (mean ZT1-6; red symbols; n = 12/strain) conditions were generally higher in D2 mice compared to AK and B6 mice ['a' (> AK), 'b' (> B6) P < 0.05; post-hoc Tukey]. No genotype differences were observed for ldha expression (not shown). B) Mean (± 1SEM; n = 12/genotype) slope of the regression lines quantifying the relationship between SD duration (1-, 3-, and 6 h) and clock-gene expression (fraction/h; see Fig.1) in the forebrain of AK, B6, and D2 mice. Changes in expression were affected by genotype (2-way ANOVA: 'genotype'-'ZT' interaction: per1: P = 0.0002; per2: P = 0.032; dbp: P = 0.0002). Slopes were steepest for D2 mice and the strain distribution pattern for this phenotype seemed to negatively correlate with the increase of EEG delta power (%/h) during wakefulness (i.e., 'Process S' in lower right panel; modified from ; with permission).