Supplementary Figure 4: Appropriate expression of ChR2 in the MPA and the effective location of fiber optic fiber in the PAG.

a. Representative image of virally mediated ChR2 expression in the MPA and surrounding brain regions. b. Representative image of an individual mouse brain showing non-specific viral expression leading to reduced MPA-specific expression. Note that this mouse showed no response to objects during photostimulation. c. Quantification of viral expression in the MPA and surrounding brain regions (n = 17 mice; RM ANOVA on Ranks, MPA vs. LPO, P < 0.05; MPA vs. VLPO, P < 0.05; MPA vs. vBNST, P < 0.05; MPA vs. SHy, P < 0.05). d. Schematic depiction of retrograde tracing from vPAG. Bottom, Representative image of the MPA and surrounding brain regions. Note that labeled neurons project to the vPAG. e. Representative image of retrograde tracing. 3 mice were used for this image. f. Quantification of labeled neurons in the MPA and surrounding brain regions (n = 3 mice; One Way RM ANOVA, MPA vs. LPO, P = 0.002; MPA vs. VLPO, P = 0.001; MPA vs. vBNST, P = 0.001; MPA vs. SHy, P = 0.002). g. Locations of the fiber optic cannulas in the vPAG. The red crosses indicate the optic fiber tip locations in mice that responded to an object (n = 6) during photostimulation of the MPA-vPAG circuit; the black crosses indicate tip locations in mice that showed no response (n = 3). Scale bars, 200 µm. Bar graphs indicate mean (bars) ± SEM (error bars) and individual data (circles). See the detailed statistical values in Supplementary table 1. * P < 0.05