PREFRONTAL CORTEX AND CAUDATE-NUCLEUS IN CONDITIONAL ASSOCIATIVE LEARNING - DISSOCIATED EFFECTS OF SELECTIVE BRAIN-LESIONS IN RATS

Rats with lesions to prefrontal cortex (PFC) or caudate nucleus (CN) w ere compared on tests of conditional associative learning (GAL) that p laced varying demands on conditional rule learning and working-with-me mory operations that are essential for response selection. Damage to e ither structure impaired performance, but the respective deficits resu lted from disruption of different processes. CN lesions produced a con sistent learning deficit that was thought to reflect a basic impairmen t in forming stimulus-response (S-R) associations. The behavior of PFC rats was more Variable and depended on task requirements. When S-R le arning or response selection was relatively easy, the PFC was not crit ical. However, when either component was made more difficult, thus req uiring the contribution of strategic processes, PFC damage produced pr ofound impairments. In addition to clarifying the roles of the PFC and CN in GAL, the results provide further evidence that multiple brain r egions participate in relatively simple behavioral tasks and that thei r respective contributions can be dissociated.