AMNESIA, MEMORY AND BRAIN SYSTEMS

Bilateral damage to either the medial temporal lobe or the diencephali c midline causes an amnesic syndrome, i.e. a global impairment in the ability to acquire new memories regardless of sensory modality, and a loss of some memories, especially recent ones, from the period before amnesia began. The memory deficit can occur against a background of in tact intellectual and perceptual functions. Two themes have been promi nent in recent work. First, the amnesic syndrome is narrower than once believed in the sense that a number of learning and memory abilities are preserved (e.g. skill and habit learning, simple forms of conditio ning and the phenomenon of priming). Second, the brain system damaged in amnesia has only a temporary role in memory. As time passes after l earning, memory is reorganized and consolidated within neocortex, such that eventually medial temporal lobe and diencephalic structures are not needed for storage or retrieval.