Amnesia
Amnesia, loss or impairment of memory. Amnesia is usually associated with some form of brain damage, but it may also be caused by severe psychological trauma. Amnesia with a physical cause is called organic amnesia, whereas amnesia of psychological origin is called functional amnesia. Amnesia varies in its degree of severity. For example, a mild concussion may cause a person to forget recent events, but the memory loss may last only for several hours. On the other hand, severe head injuries may lead to permanent memory loss and an inability to learn new information. Amnesic individuals may retain normal cognitive abilities in other areas, such as language. Anterograde amnesia is impairment in the ability to lay down new memories. It typically results from damage to the areas of the brain involved in long-term memory, including the hippocampus, the temporal lobes, and the frontal lobes. Such damage may result from brain infection ( encephalitis ), alcoholism, stroke , anoxia (severe ox