Memory and amnesia: resistance to disruption develops for years after learning

Psychiatric patients were asked to recall as much as possible about former television programs that broadcast for only one season (1967-1974). After five prescribed electroconvulsive treatments, recall was markedly impaired for events that occurred 1 to 2 years before treatment and not affected for events that occurred prior to that time. A quantitative and qualitative analysis of the facts recalled from each time period permitted consideration of several possible explanations of this temporally graded amnesia. The data strongly support the conclusion that the neural substrate of long-term memory changes for years after learning and that resistance to amnesia develops as a consequence of these changes.