Fig. 3. Predictability modulates reward responses in trained mice.
a, Schematic of reward perturbation experiments: during each behavioral session, we randomly interspersed random rewards (10% of inter-trial intervals) or tone-cued rewards (also 10% of inter-trial intervals; 500 ms delay between cue onset and reward). b, Top: trial-averaged population response of a representative FOV (same as Fig. 2) to random, operant and tone-cued rewards. ROIs are sorted first by mediolateral position of identified microzones, then mediolaterally within each microzone. Color blocks adjacent to each heatmap denote microzonal designation, following the color scheme of Fig. 2 (gray, unclustered). Middle: trial-averaged steering wheel velocity. Bottom: trialaveraged licking. Velocity and licking are shown as mean ± s.e.m. across trials (n = 30 random rewards, 156 trial rewards and 30 tone-cued rewards). Scale bar, 500 ms. c, Scatter plots showing pairwise comparisons of response amplitude (computed as mean over 0 to +100 ms after each event) across different reward conditions; n = 891 neurons from 5 FOVs in 5 mice. Data points from representative FOV (b) are shown in darker gray. d, Cell-wise average of Purkinje cell dendritic response to each reward-related event. Data are shown as mean ± s.e.m. (n = 891 neurons from 5 FOVs in 5 mice, Kruskal-Wallis test, H = 460, d.f. = 3, P = 2×10−99, significance values for Bonferroni-corrected individual comparisons: random versus trial reward, P = 2×10−18; random versus cued reward, P = 3×10−33; trial versus cued reward, P= 0.009; trial reward versus tone cue, P = 1×10−57; cued reward versus tone cue, P= 5×10−82). e, Summary of Pearson’s correlations between pairs of reward-related events. Data are shown as box plots: center line, median; box edges, interquartile range; whiskers, range without outliers; gray points, outliers (n = 891 neurons from 5 FOVs in 5 mice, Kruskal-Wallis test, H = 237, d.f. = 3, P = 5×10−51, significance values for Bonferroni-corrected individual comparisons: random and trial reward versus random and cued reward, P= 7×10−32; random and trial reward versus trial and cued reward, P = 3×10−35; random and cued reward versus trial and cued reward, P>0.9; random and cued reward versus random reward and tone cue, P = 1×10−17; trial and cued rewards versus random reward and tone cue, P = 4×10−20). f, Time course of mean responses across reward conditions for Purkinje cells in reward-activated microzones (top, n = 361 neurons) and reward-suppressed microzones (bottom, n = 470 neurons). Scale bar, 250 ms. Note that 60 neurons were not clustered into a microzone and excluded from this analysis. Data are shown as mean ± s.e.m. Statistics summary: n.s., not significant, **P<0.01, ***P<0.001.