LED driver. In both two-step and reversal learning tasks, on stimulation trials red light (50mW, 630nM) was delivered from when the subject entered the side poke and received the trial outcome, until the subsequent choice, up to a maximum of 6 s. Stimulation was delivered on a randomly selected 1/6 (17%) of trials, with a minimum of 2 non-stimulated trials between each stimulation trial followed by a 0.25 probability of stimulation on each subsequent trial. At the end of behavioral experiments, animals were sacrificed and perfused with paraformaldehyde (4%). The brains were sectioned in 50um coronal slices and the location of viral expression was characterized with fluorescence microscopy (Figure S6).
