Figure 3. Caudate microstimulation affected the monkeys’ decision behavior.

(A, B) Two example sessions from monkey C showing different patterns of microstimulation effects. Black: trials without microstimulation; red: trials with microstimulation. Open circles and dashed lines: data and fits for blocks in which the ipsilateral choice was paired with large reward and the contralateral choice was paired with small reward. Filled circles and solid lines: data and fits for blocks in which the ipsilateral choice was paired with small reward and the contralateral choice was paired with large reward. Abscissa: signed coherence (positive: motion was toward the contralateral target; negative: motion was toward the ipsilateral target). Top panels: probability of making the contralateral choice. Lines are logistic fits to the choice data. Middle and bottom panels: mean reaction time (RT) for the two reward contexts. Circles and crosses represent correct and error choices, respectively. Lines: linear fits to single-trial RT data. (C, D) Summary of effects induced by microstimulation for both reward contexts (C, estim terms) and by interactions between microstimulation and reward context (D, rew × estim terms). The top rows illustrate the effects on psychometric and chronometric curves for positive values of the corresponding terms. Bottom rows show the histograms of changes in choice bias (logistic shift in %coh), perceptual sensitivity (logistic slope in 1/%coh), and intercept and slope of linear regression of RT as a function of unsigned motion coherence. Thick vertical lines indicate the median values. Green lines, Wilcoxon signed-rank test, p<0.05.

Figure 3—figure supplement 1. Effects of caudate microstimulation for all sessions.

(A) Scatter plots for microstimulation-induced effects for the Ipsi-LR blocks (x-axis) and Contra-LR blocks (y-axis). A1, choice bias (logistic shift in %coh, positive: biasing toward the contralateral choice). A2: perceptual sensitivity (logistic slope in 1/%coh, positive: increasing sensitivity). A3 and A4: intercept (ms, A3) and slope (ms/|%coh|, A4) of linear fits to RT for contralateral saccades. A5 and A6: corresponding values for ipsilateral saccades. Magenta circles: sessions with significant effects for monkey C. Green circles: sessions with significant effects for monkey F. Labels (a, b) correspond to the example sessions in Figure 3A and B, respectively. Lines with triangles on the histograms: median values. Green lines, Wilcoxon signed-rank test, p<0.05. (B) Scatter plots for microstimulation-induced effects that were reward context-independent ("estim", x-axis) and -dependent ("rew × estim", y-axis). Red circles: sessions in which both “estim” and “rew × estim” measurements from the original data were outside the 95% confidence intervals of measurements from shuffled data (the designations of trials with and without microstimulation were shuffled for each session 200 times). Green circles: only one measurement was outside the confidence intervals. The values correspond to illustrations in Figure 3C and D. The histograms are the same as those in Figure 3C and D. Labels (a, b) correspond to the example sessions in Figure 3A and B, respectively. Lines with triangles on the histograms: median values. Green lines, Wilcoxon signed-rank test, p<0.05.

Figure 3—figure supplement 2. The average RT difference between the two reward contexts alone could not account for the reward context-dependent microstimulation effects.

(A) The average RT was longer for Ipsi-LR and Contra-LR blocks for the two monkeys, respectively (Wilcoxon signed rank test, p=0.002 and <0.0001). Data were from trials without stimulation. Dashed line: unity slope. Each circle represents one session. (B) Results of linear regressions using the difference in average RT between reward context as the independent variable and the rew × estim effects in Figure 3D as the dependent variables. %EV: percentage of variance explained by the difference in RT. Note the low %EV values for most regressions.