The aPFC may not encode only the value of an alternative

choice but also information about the diversity of alternative options available. Yoshida and Ishii (2006) trained their subjects to navigate through a virtual maze and then took fMRI scans while the subjects tried to work out where they had subsequently been placed within the maze. The BOLD signal in an aPFC region just anterior to that highlighted by Boorman et al. (2009) Doxorubicin manufacturer varied with the subjects’ uncertainty about their position in the maze and therefore with the range of alternative options that the subjects might reasonably choose as their next response. In other words, aPFC activity increases when one considers many alternative options as opposed to just a few. While aPFC may encode the number of possible alternative choices it is important to note that it does not code all options in the same way. The representation of one alternative, the one with the highest value, seems to have a special status. Boorman et al. (2011) tested subjects on a decision-making task with three choices. They found a positive correlation between aPFC BOLD signal and the value of the better alternative choice. There was, however, a negative relationship between aPFC BOLD signal

selleck and the value of both the chosen option and the worse alternative. It seems, therefore, that aPFC activity reflects the benefits of switching to the better alternative and the opportunity cost of switching away from both the current choice and the other worse alternative. Such a pattern of activity with just one alternative choice held in a pending state suggests that not all potential alternative choices are considered equally when we change our minds and pursue a different course of action. Behavioral evidence also suggests that we are not able to represent all alternative choices equally and that we switch more effectively to one alternative as opposed to another at any given time (Boorman

et al., 2011 and Charron and Koechlin, 2010). The same aPFC region has also been identified in a study of exploratory decision-making (Daw et al., 2006). Although it is obviously advantageous for organisms to choose the most valuable option they can identify it is essential that they also through explore alternative options; an organism that fails to explore alternatives will fail to identify choices that might be even higher in value, especially when the environment is changing. There is, therefore, a balance to be struck between exploiting choices of known value and exploring alternatives. Daw et al. (2006) found that vmPFC/mOFC activity was highest when exploitative choices of high-value options were being made but aPFC was more active when lower value, presumably exploratory, choices were made. The results reported by Boorman et al., 2009 and Boorman et al., 2011 suggest that the high-aPFC signal during exploration reported by Daw et al.