Figure 4. Quantitative comparison of value modulation of GPe Slow Pacemakers and VTA dopamine cells.

(A) Responses of GPe Slow Pacemakers (red) and VTA dopamine cells (green) to key events in both tasks. Circles plot the peak response for each cell. Filled circles denote statistically significant responses while open circles are not significantly different from the baseline rate (p < 0.01, see Methods). Top, percentages of cells exhibiting significant responses. Horizontal lines mark the median significant responses; boxes show interquartile ranges. The only significant population-level differences between GPe Slow Pacemakers and VTA dopamine cells (comparing responding cells only) were in the response to the Go cue and the response following side in when reward was omitted (marked by asterisks, Wilcoxon signed rank test, p < 0.05). See Figure S4 for responses in other cell types.

(B) RPE encoding by GPe Slow Pacemakers (red) and VTA dopamine cells (green) in both tasks. Circles plot the regression slope for peak firing rate change against value as a function of the coefficient of determination (r²) for each cell. Filled circles denote regression slopes significant different from zero while open circles are not significant (p < 0.01). Percentages give the fraction of cells exhibiting significant regression slopes (positive or negative). For the Pavlovian task, the left panel shows results for the CS response while the right panel shows the US response (rewarded trials only). For the instrumental task, both panels show results for “side in,” but the left panel is rewarded trials (positive RPE) while the right panel is unrewarded trials (negative RPE).

(C) Cumulative distributions of response latencies of GPe slow pacemakers (red) and VTA dopamine cells (green) to key events. Only statistically significant excitatory responses are included. 1^st panel, all conditioned stimuli in the Pavlovian task regardless of cued reward probability. This includes VTA data using different reward probabilities (50% / 100%) that are excluded from all other analyses (combined, n=29). 2^nd panel, reward delivery (Pavlovian). 3^rd panel, visual “light on” event, “engaged” trials only. 4^th panel, auditory “Go cue.” 5^th panel, reward delivery (instrumental). Dashed lines mark the median.