Specialisation within the prefrontal cortex: the ventral prefrontal cortexand associative learning

This paper provides evidence that the ventral prefrontal cortex plays a rol e in the learning of tasks in which subjects must learn to associate visual cues and responses. Imaging with both positron-emission tomography (PET) a nd functional magnetic-resonance imaging (fMRI) reveals learning-related in creases in activity when normal subjects learn visual associative tasks. Ev idence is also presented from an event-related fMRI study that activity in this area is time-locked both to the presentation of the visual stimuli and also to the time of the motor response. Finally, it is shown in a study of monkeys that removal of the ventral prefrontal area 12 (including 45 A) im pairs the ability of monkeys to relearn a visual associative task (visual m atching), even though there were no demands on working memory. It is, there fore, proposed that the ventral prefrontal cortex constitutes part of the c ircuitry via which associations are formed between visual cues and the acti ons or choices that they specify. On the basis of the existing anatomical a nd electrophysiological data, it is argued that the prefrontal cortex is th e only area that can represent cues, responses and outcomes.