MSH: Pathologic partial or complete loss of the ability to recall past experiences (AMNESIA, RETROGRADE) or to form new memories (AMNESIA, ANTEROGRADE). This condition may be of organic or psychologic origin. Organic forms of amnesia are usually associated with dysfunction of the DIENCEPHALON or HIPPOCAMPUS. (From Adams et al., Principles of Neurology, 6th ed, pp426-7),NCI: A disorder characterized by systematic and extensive loss of memory.,NCI: Systematic and extensive loss of memory caused by organic or psychological factors. The loss may be temporary or permanent, and may involve old or recent memories.