Latent inhibition is a learning phenomenon where pre-exposure to a neutral stimulus reduces learning rates for that stimulus. (a) Mice (n=7; 5 males, 2 females) were pre-exposed to a stimulus (Pre-exposed CS+) for 4 sessions. (b) The pre-exposed CS+ as well as a novel stimulus (CS+) were paired with a footshock for 2 sessions. A novel stimulus (CS−) was presented between each CS+ presentation and signaled the absence of the footshock. (c) Freezing to the pre-exposed CS+, CS+, and CS− were measured (session 1, for session 2 see Extended Data Fig. 4). There was a main effect of pre-exposure (RM ANOVA F(2,12)= 11.50, p=0.001) and freezing was higher to the CS+ than the pre-exposed CS+ (Tukey post-hoc p=0.035). Freezing was increased to the CS+ as compared to the CS− (Tukey post-hoc p=0.001) (d) Percentage of time freezing across sessions 1. Freezing to the CS+ was greater than the pre-exposed CS+ (RM ANOVA main effect of pre-exposure F(1, 8)= 9.76 p=0.014, n=5 mice). (e-f) Trial-by-trial dopamine response (z-scores) to the CS+ and (c) pre-exposed CS+ (n=5 mice for each trial; 6 trials in total). (g) Averaged dopamine response over trials. ITI (inter-trial interval), averaged dopamine response during the time between CS+ presentations in the same session. (h) Peak dopamine response to the CS+ was higher than the ITI responses (Nested ANOVA F(2,113)= 2.51, p=0.0006, Bonferroni post-hoc: CS+ vs. pre-exposed CS+ p=0.08; CS+ vs. ITI p=0.0002; n=30 trials, n=5 mice); pre-exposed CS+ did not differ from the ITI responses (Bonferroni post-hoc p=0.32). (i) Time for dopamine to return to baseline was slower for the CS+ compared to the pre-exposed CS+ (Nested ANOVA F(2,113)= 19.70, p=0.0001, Bonferroni post-hoc p<0.0001; n=30 trials, n=5 mice) and the ITI dopamine response (Bonferroni post-hoc p<0.0001). (j) Tau (time in for signal to return to 2/3 of peak) did not change between CS+ and pre-exposed CS+ (Nested ANOVA F(2,113)= 2.13, p=0.123, Bonferroni post-hocs: p>0.05). Data represented as mean ± S.E.M., * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001, ns = not significant.