The most common form of memory disorder involves difficulties in forming new memories. A severe example is anterograde amnesia, a rare condition which can result from brain injury or disease.
Another severe type of memory disorder is called retrograde amnesia. Retrograde amnesia is also usually caused by brain injury or disease. In this condition, individuals have trouble remembering events in their life that occurred prior to the brain injury.
Amnesia refers to the loss of memory. Memory loss may result from two-sided (bilateral) damage to parts of the brain vital for memory storage, processing, or recall (the limbic system, including the hippocampus in the medial temporal lobe).
People who experience amnesia have been instrumental in helping brain researchers determine how the brain processes memory. Until the early 1970s, researchers viewed memory as a single entity. Memory of new experiences, motor skills, past events, and previous conditioning were grouped together in one system that relied on a specific area of the brain.