To assess functional interaction between the medial temporal lobe (MTL) and prefrontal cortex (PFC), 5 animals received lesions of the MTL (hippocampus and parahippocampal gyrus: HF+) in one hemisphere and the prefrontal cortex (areas 46 and 9) in the other plus a commissural split (callosum and anterior commissure) to disconnect the intact MTL and PFC (group CFHS). As a surgical control, 4 animals were given HF+ and PFC lesions in the same hemisphere along with a commissural split leaving the MTL and PFC intact and interconnected in the other hemisphere (group IFHS). We previously reported (SFN 2003) that monkeys in group CFHS were impaired on Delayed Non Match to Sample Acquisition and Delays relative to the control group (IFHS). To further explore the interaction between PFC and MTL we administered the Delayed Recognition Span Task (DRST), assessing working memory performance with increasing memory load and the Conceptual Set Shifting Task (CSST), a test analogous to the human Wisconsin Card Sorting Tes...