Dissociable functions in the medial and lateral orbitofrontal cortex: evidence from human neuroimaging studies

Recent imaging studies show that the orbitofrontal cortex (OFC) is activated during a wide variety of paradigms, including guessing tasks, simple delayed matching tasks and sentence completion. We suggest that, as with other regions of the prefrontal cortex, activity in the OFC is most likely to be observed when there is insufficient information available to determine the appropriate course of action. In these circumstances the OFC, rather than other prefrontal regions, is more likely to be activated when the problem of what to do next is best solved by taking into account the likely reward value of stimuli and responses, rather than their identity or location. We suggest that selection of stimuli on the basis of their familiarity and responses on the basis of a feeling of 'rightness' are also examples of selection on the basis of reward value. Within the OFC, the lateral regions are more likely to be involved when the action selected requires the suppression of previously rewarded responses.