The role of prefrontal cortex in object-in-place learning in monkeys

Previous ablation studies in monkeys suggest that prefrontal cortex is involved in a wide range of learning and memory tasks. However, monkeys with crossed unilateral lesions of frontal and temporal cortex are unimpaired at concurrent object-reward association learning but are impaired at conditional learning and the implementation of memory-based performance rules. We trained seven monkeys preoperatively on an associative learning task that required them to associate objects embedded in unique complex scenes with reward. Three monkeys then had crossed unilateral lesions of frontal and inferior temporal cortex and the remaining monkeys had bilateral prefrontal cortex ablation. Both groups were severely impaired postoperatively. These results show that both bilateral prefrontal cortex ablation and frontal-temporal disconnection impair associative learning for objects embedded in scenes. The results provide evidence that the function of frontal-temporal interactions in memory is not limited to conditional learning tasks and memory-dependent performance rules. We propose that rapid object-in-place learning requires the interaction of frontal cortex with inferotemporal cortex because visual object and contextual information which is captured over multiple saccades must be processed as a unique complex event that is extended in time. The present results suggest a role for frontal-temporal interaction in the integration of visual information over time.