Single neurons in prefrontal cortex encode abstract rules

The ability to abstract principles or rules from direct experience allows b ehaviour to extend beyond specific circumstances to general situations. For example, we learn the 'rules' for restaurant dining from specific experien ces and can then apply them in new restaurants. The use of such rules is th ought to depend on the prefrontal cortex (PFC) because its damage often res ults in difficulty in following rules(1). Here we explore its neural basis by recording from single neurons in the PFC of monkeys trained to use two a bstract rules. They were required to indicate whether two successively pres ented pictures were the same or different depending on which rule was curre ntly in effect. The monkeys performed this task with new pictures, thus sho wing that they had learned two general principles that could be applied to stimuli that they had not yet experienced. The most prevalent neuronal acti vity observed in the PFC reflected the coding of these abstract rules.