Fig. 2.

Varying reward magnitudes elicit distinct regional dopamine (DA)-signal profiles. (A) Food-pellet rewards of different magnitudes were delivered into the food magazine (Top) in semirandom order on a variable ITI of 30 s. Rats received a reward of either nine food pellets (15% of trials), three food pellets (15% of trials), or one food pellet (70% of trials) (Bottom). (B) Changes in extracellular dopamine concentration in NAS, NAC, DMS, DLS, VLS, and TS in response to the unpredicted delivery of one, three, or nine food pellets (traces are aligned to reward delivery). (C) Data from B displayed as a percentage of maximum (average) dopamine release. (D) Dopamine release in response to reward was increased in all striatal regions when compared with baseline (B). Dopamine release in NAS, NAC, DMS, and DLS scaled with reward magnitude, but not in VLS and TS. Bar graphs depict (positive) peak concentrations of dopamine averaged across rats for baseline (−2 to 0 s) and reward (0 to 10 s) epochs. +, a main effect of reward magnitude, but without post hoc difference. (B and D) Data are reported as mean + SEM. Comparison to baseline (B): #P < 0.05, ##P < 0.01, ###P < 0.001; Comparison 1 vs. 3 vs. 9: *P < 0.05, **P < 0.01, ***P < 0.001.