Dissociable mechanisms of attentional control within the human prefrontal cortex

Neuropsychological tests that require shifting an attentional set, such as the Wisconsin card Sorting Test, are sensitive to frontal robe damage. Alth ough little information is available for humans, an animal experiment sugge sted that different regions of the prefrontal cortex may contribute to set shifting behavior at different levels of processing. Behavioral studies als o suggest that set shifting trials are more time consuming than non set shi fting trials (i.e. switch cost) and that this may be underpinned by differe nces at the neural level, We determined whether there were differential neu ral responses associated with two different levels of shifting behavior, th at of reversal of stimulus-response associations within a perceptual dimens ion or that of shifting an attentional set between different perceptual dim ensions. Neural activity in the antero dorsal prefrontal cortex increased o nly in attentional set shifting, in which switch costs were significant. Ac tivity in the postero-ventral prefrontal cortex increased not only in set s hifting but also in reversing stimulus-response associations, in which swit ch costs were absent. We conclude that these distinct regions in the human prefrontal cortex provide different levels of attention control in response selection. Thus, the antero-dorsal prefrontal cortex may be critical for h igher order control of attention, i.e. attentional set shifting, whereas th e postero-ventral area may be related to a lower level of shift, i.e. reorg anizing stimulus-response associations.