In the macaque monkey, disconnection syndromes can be produced experimentally either by selective section of axonal pathways or by crossed unilateral asymmetrical ablations. Behavioural investigation of the effects of these disconnections gives information that cannot be derived either from clinical studies or from the effects of bilateral symmetrical ablations in the monkey. Disconnection experiments are particularly suited to the study of the inter-actions between the components of widespread cortical networks. We propose that memory acquisition is dependent on plastic cortical changes that are widespread, rather than limited to the medial temporal lobe. Further, memory acquisition depends on cortical-sub-cortical interactions to a greater extent than memory retrieval does. Prefrontal cortex, we suggest, is specifically important in the representation of temporally complex events.