Figure 4. Providing phasic activity in D2-expressing NAc cells during the decision period decreased risky choices in risk-seeking rats.

a, NAc cell bodies expressing AAV8-D2SP-eChR2(H134R)-eYFP were stimulated bilaterally during the decision period. b, AAV8-D2SP-eChR2(H134R)-eYFP expression in NAc. AC, anterior commissure. Rectangle indicates fibre location. c, NAc cells expressing D2SP-eChR2-eYFP track 1-s 20-Hz optical stimulation (indicated by blue bars) in acute slices (representative trace; similar behaviour seen in 5 out of 5 cells). d–i, NAc D2R⁺ cell decision-period stimulation decreased risky choices in risk-seeking rats, but not risk-averse rats relative to YFP-expressing controls (n =8 risk-seeking plus eChR2, 8 risk-seeking plus eYFP, 20 risk-averse plus eChR2, 26 risk-averse plus eYFP; two-way ANOVA, interaction F_1,58 =25.37, P < 0.0001; Bonferroni post-hoc test revealed a significant difference between ChR2-expressing and YFP-expressing risk-seeking rats, but no difference between experimental and control risk-averse rats; ***P < 0.001). Grey traces represent individual animals. Black and red traces represent the population mean. Error bars represent s.e.m. Blue boxes indicate days with decision-period stimulation. j, Stimulation significantly decreased risk-seeking choices on a single-trial basis in risk-seeking rats (n = 6 rats; repeated-measures ANOVA, F_5,10 =5.504, ***P = 0.0006; Dunnet’s post-hoc test revealed the probability of choosing risky on stimulation trials was significantly lower than each other trial independently, correcting for multiple comparisons; P < 0.01 in every case). Blue bars represent the mean likelihood of risky choice across rats; red lines represent the behaviour of individual rats.