, 2009). This suggests a more flexible learning mechanism often referred

to as model-based reinforcement learning than a simple, model-free reinforcement learning (Sutton and Barto, 1998, Daw et al., 2005, Daw et al., 2011, Pan et al., 2008 and Gläscher et al., 2010). In the present study, we found that the proportion of the neurons encoding the signals related to actual and hypothetical outcomes was similar for DLPFC and OFC. For actual outcomes, this was true, regardless of whether the signals differentially modulated by the outcomes from specific actions were considered separately or not. By contrast, for hypothetical outcomes, DLPFC neurons were more likely to encode the hypothetical outcomes related to specific actions. The effect size of the signals Veliparib related to both actual and hypothetical

Gamma-secretase inhibitor outcomes were larger in the OFC than in the DLPFC, suggesting that OFC might play a more important in monitoring both actual and hypothetical outcomes. Nevertheless, the difference between these two areas was less pronounced when the activity modulated differentially by the outcomes from different actions was considered separately. In particular, the effect size of the signals related to the hypothetical outcomes from specific choices was not different for the two areas. Thus, the contribution of DLPFC in encoding actual and hypothetical outcomes tends to focus on outcomes from specific choices. The bias for DLPFC to encode hypothetical outcomes from specific actions is consistent

with the previous findings that DLPFC neurons are more likely to encode the animal’s actions than much OFC neurons. This was true regardless of whether the chosen action was determined by the external stimuli (Tremblay and Schultz, 1999 and Ichihara-Takeda and Funahashi, 2008) or freely by the animal (Wallis and Miller, 2003, Padoa-Schioppa and Assad, 2006 and Seo et al., 2007). In addition, DLPFC neurons often encode the specific conjunction of the animal’s actions and their outcomes (Barraclough et al., 2004 and Seo and Lee, 2009). Nevertheless, the interplay between DLPFC and OFC is likely to contribute to multiple aspects of decision making. For example, neurons in the OFC tend to encode the information about the animal’s action and expected outcomes during the time of feedback, and might play an important role in updating the values of different actions (Tsujimoto et al., 2009 and Sul et al., 2010). The results from the present study suggest that signals related to the actual and hypothetical outcomes might be combined with those related to the animal’s actions, not only in DLPFC but also in OFC.