It is unlikely that differences in behavioral performance among the three animal groups are attributable to differences in trial duration. First, even though trial duration varied across animal groups, mean trial durations of the three animal groups did not match their behavioral performances (a). Second, similar results were obtained in comparisons of behavioral performances of CNO and DMSO animal groups after matching their trial durations (b,c). We could not perform the same trial duration-matching analysis between CNO and eGFP-CNO D2R-Cre animal groups because the overlap in trial duration distribution between the two groups was relatively small. Note, however, that trial duration was shorter, rather than longer, in CNO compared with eGFP-CNO D2R-Cre animal groups. Furthermore, an additional test revealed that the performance of eGFP D2R-Cre mice was similar under CNO-injection and no-injection conditions (d). Also note that trial duration was not significantly different between CNO and eGFP-CNO D1R-Cre animal groups during stages 4 and 5 (a). Collectively, these results indicate that impaired performance following D1R or D2R neuronal inactivation cannot be attributed to impaired movement of the animals. (a) Mean (± SD) trial durations of the three animal groups during the reversal task. *p<0.05, **p<0.01, ***p<0.001 (one-way ANOVA followed by Bonferroni post-hoc tests). (b) Mean trial durations were matched between CNO and DMSO animal groups for each stage of the reversal task for each mouse line by deleting long trial-duration sessions of CNO mice and short trial-duration sessions of DMSO mice; numbers above bars indicate the number of sessions deleted from the total of 418 CNO-hM4Di sessions and 380 DMSO-hM4Di sessions. Error bars, SD. (c) Mean (± SEM) percentages of correct choices for trial duration-matched CNO and DMSO animal groups. The format is the same as that in Figure 2. ***p<0.001 (two-way between-groups ANOVA, stage 4, main effect of mouse line, F(1,35) = 4.29, p = 0.045; main effect of drug, F(1,35) = 37.45, p = 3.9 × 10−7; mouse line × drug interaction, F(1,35) = 2.19, p = 0.147; stage 5, main effect of mouse line, F(1,35) = 0.26, p = 0.610; main effect of drug, F(1,35) = 31.2, p = 2.7 × 10−6; mouse line × drug interaction, F(1,35) = 1.08, p = 0.305). (d) Performances of eGFP D1R-Cre and D2R-Cre mice with and without CNO injection. The target location was reversed twice in each session (2 × within session reversal). Left, daily performances; right, mean (± SEM) performances. The CNO behavioral data is identical to that during stage five in Figure 2.