Supplementary Figure 1: Comparison of behavioral performance in two variants of SST

(a) Distributions of SSRT estimates in the two SST variants (Stop Reward: n = 19 rats, 543 sessions; Stop No Reward: n = 8 rats, 466 sessions). While rats were not required to stop in the Stop No Reward Task, they nonetheless showed rapid behavioral stopping to the stop signal, with similar SSRTs as in the Stop Reward Task. (b) The proportion (mean ± s.e.m.) of failure-to-stop (FS) and successful stop (SS) trials in the two SST variants at each of the five SSDs. SSD1 is always 0ms such that the tone and light were presented simultaneously. The remaining four SSDs were evenly spaced in 40ms steps and adjusted by experimenters between sessions. Rats failed to stop more often at longer SSDs in both variants of the SST. The similarity of SSRTs in both SST variants suggests that the rapid behavioral stopping in the SST does not depend on the knowledge that successful stopping is rewarded. (c) Wait time, the latency between stop signal onset and fixation port exit, was significantly longer in successful stop trials when stopping was rewarded (independent samples t-test). Individual animals (points) are plotted along with group mean (red), ± 1.96 s.e.m. (red shaded area) and ± 1 s.d. (blue) (n=19, 8; number of animals in the two SST variants) (d). The proportion of stop trials in which rats approached the reward port and licked at least three times was significantly higher in the Stop Reward Task than in the Stop No Reward Task. Conventions as in panel (c).