Statistical Analysis
The sample size and animal numbers were determined by power analysis of pre-existing data (Belujon and Grace, 2014; Chang and Grace, 2014; Belujon et al., 2016; Salin et al., 2021).
Data were analyzed with the statistical program GraphPad Prism (Version 8.0.1; GraphPad Prism, RRID:SCR_002798).
All the results are expressed as the mean ± SEM. A Grubb’s test was used to identify statistical outliers’ animal. There was no outlier in this study. The level of probability (P ), for determining groups’ differences, was set at P  < 0.05. We followed significant main effects and interactions (P  < 0.05) with post hoc tests (Sidak’s multicomparison test) which were conducted only if the F values in the analyses achieved the appropriate level of statistical significance and the statistical measures of homogeneity of variance were not significant.
For active/inactive responses in yoked saline animals, a two-way repeated measure (RM) ANOVA was performed with session as the within-subject factor and number of nose-pokes as the between-subject factor. Since corresponding data for cocaine animals did not pass normality test, a mixed-effects model was used. For incubation of cocaine craving, a paired Mann Whitney’s test was performed.
Electrophysiological data were analyzed using either a two-way ANOVA with time (WD1-3 and WD26-45) and drug (saline and cocaine) as factors followed by Sidak’s post-hoc when comparing more than two experimental conditions. When comparing two groups, first a Kolmogorov-Smirnov normality test was used. If data passed the normality test, a unpaired t-test was used; otherwise, an unpaired Mann Whitney’s test was used.
Complete statistical analyses and exact P values are reported in Table S1.