We focused on the boundary between anterior cingulate regions 24a and 24b and mid-cingulate regions 24a′ and 24b′ (Vogt and Paxinos, 2014). Though it has not to our knowledge been studied in the context of distinguishing flexible and automatic behaviors, there are anatomical and physiological reasons for considering a role for this region in model-based control. First, neurons in rat (Sul et al., 2010) and monkey (Ito et al., 2003; Matsumoto et al., 2003; Kennerley et al., 2011; Cai and Padoa-Schioppa, 2012) ACC carry information about chosen actions, reward, action values, and prediction errors during decision-making tasks. Where reward type (juice flavor) and size were varied independently (Cai and Padoa-Schioppa, 2012), a subset of ACC neurons encoded the chosen reward type rather than the reward value, consistent with a role in learning action-state relationships. In a probabilistic decision-making task in 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
