Fig. 4: Photostimulation of VTA^{glutamate-only} neurons is rewarding, photostimulation of VTA^GABA-only neurons is aversive, and photostimulation of dual VTA^{glutamate-GABA} neurons does not induce reward or aversion.

A Timeline for behavioral testing. B VTA injection of Con/Foff viral vectors in vglut2-Cre/vgat-Flp mice (to target VTA^{glutamate-only} neurons) and VTA photostimulation. C Glu-only-ChR2-eYFP mice (n = 7), but not Glu-only-eYFP control mice (n = 9), spent significantly more time in the laser paired chamber during the photostimulation sessions without developing conditioned place preference for the laser paired chamber (chamber × day × group: F_(10,140) = 2.93; p = 0.002). D VTA injection of Coff/Fon viral vectors in vglut2-Cre/vgat-Flp mice (to target VTA^GABA-only neurons) and VTA photostimulation. E GABA-only-ChR2-eYFP mice (n = 12), but not GABA-only-eYFP control mice (n = 9), spent significantly less time in the laser-paired chamber during the photostimulation sessions without developing conditioned place aversion for the laser-paired chamber (chamber × group × day: F_(10,190) = 5.76; p = 0.00001). F VTA injection of Con/Fon viral vectors in vglut2-Cre/vgat-Flp mice (to target VTA^{glutamate-GABA} neurons) and VTA photostimulation. G Glu-GABA-ChR2-eYFP mice (n = 8) and Glu-GABA-eYFP control mice (n = 8) spent similar time in the laser paired and non-laser paired chambers in the presence or absence of VTA photostimulation (chamber × day × group: F_(10,140) = 0.64; p = 0.77). Data are presented as mean ± SEM. Three-way ANOVA with Tukey HSD post hoc test. **p < 0.01, ***p < 0.001, against non-laser paired chamber. Source data are provided as a Source Data file.