DISSOCIATION IN PREFRONTAL CORTEX OF AFFECTIVE AND ATTENTIONAL SHIFTS

The prefrontal cortex is implicated in such human characteristics as v olition, planning, abstract reasoning and affect(1-6). Frontal-lobe da mage can cause disinhibition such that the behaviour of a subject is g uided by previously acquired responses that are inappropriate to the c urrent situation(7-9). Here we demonstrate that disinhibition, or a lo ss of inhibitory control, can be selective for particular cognitive fu nctions and that different regions of the prefrontal cortex provide in hibitory control in different aspects of cognitive processing. Thus, w hereas damage to the lateral prefrontal cortex (Brodmann's area 9) in monkeys causes a loss of inhibitory control in attentional selection, damage to the orbito-frontal cortex in monkeys causes a loss of inhibi tory control in 'affective' processing, thereby impairing the ability to alter behaviour in response to fluctuations in the emotional signif icance of stimuli. These findings not only support the view that the p refrontal cortex has multiple functions, but also provide evidence for the distribution of different cognitive functions within specific reg ions of prefrontal cortex.