Second, neuroimaging in the original two-step task has identified representation of model-based value in anterior and mid-cingulate regions, suggesting that this is an important node in the model-based controller (Daw et al., 2011; Doll et al., 2015; Huang et al., 2020). Neuroimaging in a two-step task variant also found evidence for state prediction errors in dorsal ACC (Lockwood et al., 2019), consistent with our finding that ACC represented whether state transitions were common or rare. Relatedly, neuroimaging in a saccade task found ACC activation when subjects updated an internal model of where targets were likely to appear, (O’Reilly et al., 2013).
