Organic amnesia is a neurological disorder characterized by a dense impairment of memory in the context of normal intelligence and other preserved mental abilities. Investigations of patients with this disorder have enhanced the understanding of the psychological processes involved in learning and remembering, as well as the brain organization of human memory.

Much of the current interest in memory and brain function finds its origin in the study of patient H.M., a man who, in 1953, underwent surgery for treatment of refractory seizures (Scoville and Milner, 1957). The surgery involved bilateral resection of a large portion of the medial temporal region, which includes the amygdala, hippocampus, and hippocampal gyrus. Although the surgery was successful in substantially reducing H.M.'s seizures, the procedure produced a pervasive impairment of memory (Milner, Corkin, and Teuber, 1968). Since the time of his surgery at the age of twenty-seven, H.M. has...