which reward probabilities changed in blocks, neuronal representations in rat ACC underwent abrupt changes when subjects detected a possible block transition (Karlsson et al., 2012). This suggests that the ACC may represent the block structure of the task, a form of world model, albeit based on learning about latent states of the world (Gershman and Niv, 2010; Akam et al., 2015), rather than the forward action-state transition model of classical model-based RL.
