We previously reported (SFN 2001) that monkeys with bilateral lesions of the prefrontal cortex (PFC) were more impaired, relative to normals, than monkeys with bilateral lesions of the hippocampus (HF) on postoperative acquisition of the DNMS task. Moreover, on the 10 minute delay of this task, monkeys with PFC lesions were more impaired relative to normals than HF animals. To test the hypothesis of a functional interaction between HF and PFC, a group of 5 animals received lesions of the medial temporal lobe (hippocampus and parahippocampal gyrus: HF+) in one hemisphere and the dorsal prefrontal cortex (areas 46 and 9: PFC) in the other plus a commissural split (callosum and anterior commissure) to disconnect the intact HF and PFC (group CFHS). As a control, a group of 4 animals was prepared with HF+ and PFC lesions in the same hemisphere along with a commissural split leaving the HF and PFC interconnected in the other hemisphere (group IFHS). Both groups were tested on DNMS acquisition and delays. The cro...