Freezing (absence of motion except respiration) was assessed prior to (A) and immediately after (B) three pairings of a conditioned stimulus (tone) and an unconditioned stimulus (shock). On the following day the association between the shock and the tone was tested in a completely different context. Freezing was assessed prior to (C) and after (D) re-exposure to the tone. Then, rats were returned to the original context, in the absence of tone or shock, and freezing was assessed once again (E).
*P<0.05, **P<0.01, Kruskall Wallis test with Dunn’s Multiple Comparisons Test (one or more groups did not pass normality test). ◆P< 0.05, one-way ANOVA, Bonferroni post hoc comparisons. EE enriched environment, NH normal housing, Sevo sevoflurane