To test whether ACC activity is necessary for model-based control, we silenced ACC neurons on individual trials using JAWS (Chuong et al., 2014). An adeno-associated virus (AAV) viral vector expressing JAWS-GFP under the CaMKII promotor was injected bilaterally into ACC of experimental animals (n = 11 mice, 192 sessions, 77,350 trials) (Figure S6), while GFP was expressed in control animals (n = 12 mice, 197 sessions, 71,071 trials). A red light-emitting diode (LED) was chronically implanted above the cortical surface (Figure 6A). Electrophysiology confirmed that red light (50 mW, 630 nM) from the implanted LED robustly inhibited ACC neurons (Figure 6B; Kruskal-Wallis p < 0.05 for 67 of 249 recorded cells). ACC neurons were inhibited on a randomly selected 1 of 6 trials, with a minimum of 2 non-stimulated trials between each stimulation. Light was delivered from the time when the subject entered the side port and received the trial outcome until the time of the subsequent choice (Figure 6C).
