Amnesia
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- See Amnesia (computer game) for 1986 computer game
Amnesia or amnæsia (from Greek Ἀμνησία) (see spelling differences) is a condition in which memory is disturbed. The causes of amnesia are organic or functional. Organic causes include damage to the brain, through trauma or disease, or use of certain (generally sedative) drugs. Functional causes are psychological factors, such as defense mechanisms. 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.
[edit] 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. The terms are used to categorise patterns of symptoms, rather than to indicate a particular cause or etiology. 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 generally due to a head injury (fall, knock on the head). 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.
- Long-term alcoholism or malnutrition can cause a type of memory loss known as Korsakoff's syndrome. This is caused by brain damage due to a Vitamin B1 deficiency and will be progressive if alcohol intake and nutrition pattern are not modified. Other neurological problems are likely to be present in combination with this type of Amnesia.
- Short-term memory loss is a common symptom of Alzheimer's disease and other forms of dementia.
- 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. This can include:
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- Dissociative amnesia is used to refer to inability to recall information, usually about stressful or traumatic events in persons' lives, such as a violent attack or rape. Persons retain the capacity to learn new information.
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- Fugue state is also known as dissociative fugue. It is caused by psychological trauma and is usually temporary. 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" [1]. While popular in fiction, it is extremely rare.
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- Posthypnotic amnesia is where events during hypnosis are forgotten, or where past memories are unable to be recalled.
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- Lacunar amnesia is the loss of memory about one specific event.
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- Childhood amnesia (also known as Infantile amnesia) is the common inability to remember events from one's own childhood. Whilst Sigmund Freud attributed this to sexual repression, others have theorised that this may be due to language development or immature parts of the brain. This is often exploited by the use of false memories in child abuse cases.
- Global amnesia is total memory loss. This may be a defense mechanism which occurs after a traumatic event. Post-traumatic stress disorder can also involve the spontaneous, vivid retrieval of unwanted traumatic memories.
- Source amnesia is a memory disorder in which someone can recall certain information, but they do not know where or how they obtained it.
- Memory distrust syndrome is a term invented by the psychologist Gisli Gudjonsson to describe a situation where someone is unable to trust their own memory.
- Excessive short-term alcohol consumption can cause a blackout phenomenon with similar symptoms to amnesia.
[edit] 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. The TV show "Kyle XY" is based on an amnesiac boy who mysteriously appears in a forest. In the Bourne Identity, the main character has retrograde amnesia. In the 1966 motion picture "Mr. Buddwing", the protagonist enters an amnesial fugue state in response to distress in his marital relationship. In the 2004 release "Forgotten", adults struggle with memory loss about the existence of their children, who have been abducted for alien/government experiments. In movies, it is often depicted that a second hit to the head (similar to the first one) cures the amnesia. In reality, however, a second concussion would have a catastrophic consequences: a phenomenon known as Second Impact Syndrome. 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.
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