amnesia - Types of amnesia, Amnesia in fiction

Memory disability, often associated with brain damage or a traumatic event. Retrograde amnesia is the inability to remember material learned before the precipitating event. Anterograde amnesia is difficulty in learning new material. The most common form of amnesia is one in which short-term memory is adequate, long-term episodic memory (the ability to remember specific past events) is poor, and long-term semantic memory (memory for facts, such as word meanings) is relatively intact.

The causes of amnesia are organic or functional. Hysterical post-traumatic amnesia is an example of this. Amnesia may also be spontaneous, in the case of transient global amnesia. This global type of amnesia is more common in middle-aged to elderly people, particularly males, and usually lasts less than 24 hours.

Types of amnesia

In anterograde amnesia, new events are not transferred to long-term memory, so the sufferer will not be able to remember anything that occurs after the onset of this type of amnesia for more than a few moments. The complement of this is retrograde amnesia, where someone will be unable to recall events that occurred before the onset of amnesia. Both categories of amnesia can occur together in the same patient, and commonly result from damage to the brain regions most closely associated with episodic/declarative memory: the medial temporal lobes and especially the hippocampus. Traumatic amnesia is often transient; the duration of the amnesia is related to the degree of injury and may give an indication of the prognosis for recovery of other functions. Mild trauma, such as a car accident that could result in no more than mild whiplash, might cause the occupant of a car to have no memory of the moments just before the accident due to a brief interruption in the short/long-term memory transfer mechanism. A common form of dissociative amnesia involves amnesia for personal identity but intact memory of general information. Long-term alcoholism or malnutrition can cause a type of memory loss known as Korsakoff's syndrome. Other neurological problems are likely to be present in combination with this type of Amnesia. The Merck Manual defines it as "one or more episodes of amnesia in which the inability to recall some or all of one's past and either the loss of one's identity or the formation of a new identity occur with sudden, unexpected, purposeful travel away from home" . Childhood amnesia (also known as Infantile amnesia) is the common inability to remember events from one's own childhood. Posthypnotic amnesia is where events during hypnosis are forgotten, or where past memories are unable to be recalled. Psychogenic amnesia results from a psychological cause as opposed to direct damage to the brain caused by head injury, physical trauma or disease, which is known as organic amnesia. Source amnesia is a memory disorder in which someone can recall certain information, but they do not know where or how they obtained it. Excessive short-term alcohol consumption can cause a blackout phenomenon with similar symptoms to amnesia.

Amnesia in fiction

Amnesia is prevalent in many works of fiction. Global Amnesia is a common motif in fiction despite being extraordinarily rare in reality. Anterograde amnesia features in the movies Memento, Clean Slate, and 50 First Dates, and lacunar amnesia features in the movie Eternal Sunshine of the Spotless Mind. In the first season of 24, a prominent character has traumatic amnesia. In the Bourne Identity, the main character has retrograde amnesia. In movies, it is often depicted that a second hit to the head (similar to the first one) cures the amnesia. Dissociative Amnesia plays a critical role in the novel Mysterious Skin and movie of the same name. Author Gene Wolf addresses amnesia in the series "Soldier of the Mist", where the main character Latro is injured during battle, causing relatively long term (24 hour) anterograde amnesia.