Role of the Orbitofrontal Cortex in Reinforcement Processing and Inhibitory Control: Evidence from FMRI Studies in Healthy Human Subjects.

Over the last two decades, advances in neuroimaging techniques have enabled us to study regional neuronal responses in a wide variety of cognitive contexts in humans. Insights have emerged that were inaccessible to conventional neuropsychology. We have been able to study regions of the brain that are rarely focally damaged, and cognitive processes that are hard to measure empirically. One region that has aroused considerable interest in recent years is the "mysterious orbitofrontal cortex" (Cerebral Cortex, 2000), which plays a crucial role in emotional, motivational and social aspects of processing and behaviour. Various functions of this region have been proposed, including reinforcement processing and inhibitory control. There is both animal and human neuropsychology evidence implicating the orbitofrontal cortex in these processes, and that evidence is reviewed briefly here. Functional neuroimaging has allowed us the means to explore these processes in detail in humans. Imaging studies have suggested that OFC is indeed critically involved in reward processing, however its role appears to be a complex one, mediating the interaction between reinforcer value, predictability and behavioural choice. Inhibitory control has also been associated with functional responses in lateral orbitofrontal regions. Recent evidence suggests that the role of lateral orbitorfrontal cortex in inhibitory control specifically involves rapid changes of behavioural strategy in response to changing behavioural circumstances.