Amnesia refers to loss of memories, usually subsequent to some type of neurological event. The loss can be in terms of recent or distant past memories or may involve the loss of ability to form new memories.

The condition called amnesia may have either functional or organic etiology. Functional amnesia is typically caused by extreme emotional or psychological trauma. The event(s) are so overwhelming or threatening to recall that the individual pushes memories out of consciousness and renders them inaccessible. This form of amnesia is relatively uncommon. Some of the most often-cited causes of functional amnesia are: being the victim or witness to a violent crime; combat experiences; being witness or victim to terrorist acts; experiencing a natural disaster such as a tornado or tsunami; and being the victim or witness to domestic violence, child abuse, or sexual crime.

There are numerous causes of functional organic amnesia, having to do with injuries to the portions of the brain most critical for memory formation. These causes include stroke, injury to the brain, central nervous system (CNS) disease, tumors of the brain or CNS, surgery, alcoholism, long-term substance abuse, encephalitis, and electroconvulsive therapy. Contrary to the popular notion of amnesia in which a person experiences a severe head trauma and is unable to recall who or where he is or anything about the circumstances of his life, the primary symptoms of amnesia are the loss of specific types of memories and/or an inability to learn new information or to form new memories, starting from the onset of the amnesia. Amnesia can be transient (temporary) or permanent.

There are two types of amnesia: retrograde and anterograde. Retrograde amnesia refers to significantly impaired memory of past events or previously highly familiar information. Anterograde amnesia refers to a significantly impaired ability to learn and retain new information, beginning with the onset of the amnestic event. In many types of head trauma, memories of recent events are lost, either temporarily or permanently.

Amnesia, also called amnestic syndrome, does not affect cognitive efficiency. There is typically no loss of innate intelligence or reasoning ability, although there may be significant deficits in ability to recall current events. There is rarely loss of skills involved in activities important for daily life, such as reading, numerical understanding, ability to operate a motor vehicle, and performing occupational or household activities. Amnesia does not generally affect attention span, intelligence, reasoning ability, sense of humor, sense of self, or personality. Most people with amnestic syndrome have awareness of their memory deficit. Research studies on amnesia lend support to the scientific belief that multiple brain areas are involved in memory creation and storage.

Most individuals cannot readily access memories of events occurring in infancy or very early childhood. Anna Freud referred to this as infantile amnesia. The most common explanations for this phenomenon have to do with ability to encode, organize, and later access information stored before the development and acquisition of language, as well as the rapid degree of brain maturation during the first few years of life. The scientific community does not consider this a true form of amnesia.

See also Fugue ; Learning ; Memory ; Neuroplasticity .



Anderson, John R., and G. H. Bower. Human Associative Memory. Hoboken, NJ: Taylor and Francis, 2014.

Danziger, Kurt. Marking the Mind: A History of Memory. Cambridge, UK: Cambridge University Press, 2008.


Mayo Clinic. “Amnesia.” (accessed July 20, 2015).

Mayo Clinic. “Transient global amnesia.” (accessed July 20, 2015).


American Academy of Clinical Neuropsychiatry, Department of Psychiatry (F6248, MCHC-6), University of Michigan Health System, 1500 E. Medical Center Dr., SPC 5295, Ann Arbor, MI, 48109-5295, (734) 936-8269, Fax: (734) 936-9761, .


Neurologist Dr. Oliver Sacks speaks at Columbia University on June 3, 2009, in New York City.

Neurologist Dr. Oliver Sacks speaks at Columbia University on June 3, 2009, in New York City.
(© Chris McGrath/Getty Images)

Oliver Sacks’ case study entitled The Lost Mariner tells the story of a patient named Jimmie G., who was referred to Dr. Sacks in 1975, suffering from profound amnesia. Sacks describes Jimmie as a genial and handsome 49-year-old man, seemingly intact intellectually but deeply amnesic, believing the year to be 1945 and himself to be 19 years old. He is able to recall his childhood in great detail, as well as his days in the Navy during WWII. However, his memories stop there. When told the actual year and his actual age, he becomes very upset. However, just minutes later he has forgotten the entire conversation and again greets Dr. Sacks as though they had never met, illustrating the dramatic extent of his memory impairment. He did very well on intelligence testing, but tests of his memory revealed that he would forget things in minutes or even seconds. He failed to remember objects he was presented with, or even to remember that he had been asked to remember them. He did sometimes have faint memories of events but no indication of whether they took place minutes or months ago.

Sacks describes him as “aman without a past (or future), stuck in a constantly changing, meaningless moment.” He concludes that Jimmie's condition is the result of Korsakov's syndrome, a disease resulting from cerebral tumor or trauma or, classically, from alcoholism, which damages tiny mammillary bodies in the brain, causing neuron destruction. This was confirmed by notes from Bellevue Hospital, where Jimmie had been taken in 1970 after his alcoholism had worsened and, as Jimmie's brother put it, he had “gone to pieces.” This was when his memory problems emerged. The fact that he did not seem to suffer the acute effects of Korsakov's syndrome until 1970 proved that not only immediate but retrograde amnesia could occur in the syndrome as well.

There is not much hope for recovery or improvement of memory in cases of Korsakov's syndrome, but Sacks emphasizes the impact of community and surroundings on Jimmie's quality of life and condition. Jimmie begins to develop a sense of familiarity with the Catholic nursing home he is living in, sometimes recognizing employees, though often mistaking them for people from his past. The only person he recognizes consistently is his brother, and Sacks describes their “emotional visits.” However, Jimmie is still puzzled as to why his brother looks so old.

However, Sacks still notes that something about Jimmie seems “empty” and Jimmie himself says that he doesn't enjoy life, doesn't feel alive and says that he hasn't in a long time. Sacks questions whether one can be “de-souled” by a disease. However, when he sees Jimmie in the chapel, listening to music, looking at art, or gardening, he notes a dramatic change in Jimmie's affect and condition. These activities required absorption and attention, a kind of emotional and spiritual attention which was able to hold Jimmie. He took on some of the work of the gardener and even began to recognize the garden and become less disoriented. Sacks quotes Russian neuropsychologist A.R. Luria saying, “A man does not consist of memory alone. He has feeling, will, sensibility, moral being … It is here… youmay touch him and see a profound change.”

The case brings up deep questions about the nature of the self and even the soul. Like many of Sacks’ case histories, it focuses not on the idea of a “cure” but on the adaptability of the human brain and spirit. Sacks ends the case study by saying that it teaches a philosophical as well as a clinical lesson: “that in Korsakov's, or dementia . . . however great the organic damage . . . there remains the undiminished possibility of reintegration by art, by communion, by touching the human spirit: and this can be preserved in what seems at first a hopeless case of neurological devastation.”