It is an important task of future studies to try to dissociate the role of the ACC in learning the value of actions from these other interconnected regions and to discover how response costs are incorporated within such a representation. There is increasing evidence, for instance, that while the ACC appears to play a direct role in deciding which response to make, the prediction error signal encoded by dopamine neurons is not directly related to action selection (Bayer and Glimcher, 2005; Morris, Nevet, Arkadir, Vaadia and Bergman, 2006). It will be imperative to investigate, amongst other things, whether the ACCs encodes a combination of reward and previous choice history or just one of the two factors in isolation and how the context of the type of environment influences the calculation of value. While there is now a large body of research showing that the ACC uses all types of reinforcement information – rewards as well as errors – to build up a sense of action value, it is not clear how this region assigns importance to individual pieces of information.
