a, Stimulation was as in Fig. 4, except delivered during the first second of reward retrieval rather than during the 1-s decision period. b, The effect of this stimulation during the outcome period was smaller than that of stimulation during the decision period (two-way ANOVA, interaction F1,24 =6.12; *P = 0.02; Bonferroni post-hoc tests revealed a significant effect of stimulation during the decision period, P <0.001, but no effect of stimulation during the outcome period). cāh, As in Fig. 4, 1 s of 20-Hz optical stimulation of NAc DR2+ cells during the outcome period decreased risky choices in risk-seeking, but not risk-averse rats relative to YFP-expressing controls (two-way ANOVA, interaction F1,31 =4.317, P = 0.046; Bonferroni post-hoc test revealed a significant difference between eChR2-expressing and YFP-expressing risk-seeking rats, but no difference between experimental and control risk-averse rats; *P <0.05). Grey traces represent individual animals. Black and red traces represent the population average. Error bars represent s.e.m. Blue boxes indicate days on which optical stimulation was delivered during the outcome.