Name = Amnesia
| Caption =
ICD10 = ICD10|R|41|3|r|40
ICD9 = ICD9|780.9, ICD9|780.93
MeshID = D000647
Amnesia (from Greek "polytonic|Ἀμνησία") is a condition in which
memoryis disturbed. In simple terms it is the loss of memory. 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. [ [http://www.emedicine.com/neuro/topic380.htm eMedicine - Transient Global Amnesia : Article by Roy Sucholeiki ] ] This global type of amnesia is more common in middle-aged to elderly people, particularly males, and usually lasts less than 24 hours.
Another effect of amnesia is the inability to imagine the future. A recent study published online in the "
Proceedings of the National Academy of Sciences" shows that amnesiacs with damaged hippocampuscannot imagine the future. [http://www.pnas.org/cgi/content/abstract/0610561104v1 Patients with hippocampal amnesia cannot imagine new experiences] , "Proceedings of the National Academy of Sciences.] This is because when a normal human being imagines the future, they use their past experiences to construct a possible scenario. For example, a person who would try to imagine what would happen at a party that would occur in the near future would use their past experience at parties to help construct the event.
Forms of amnesia
anterograde amnesia, new events contained in the immediate memory are not transferred to the permanent as long-term memory.
Retrograde amnesiais the distinct inability to recall some memory or memories of the past, beyond ordinary forgetfulness.
The terms are used to categorize 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 drug effects or damage to the brain regions most closely associated with episodic/ declarative memory: the medial temporal lobes and especially the hippocampus.
An example of mixed retrograde and anterograde amnesia may be a motorcyclist unable to recall driving his motorbike prior to his head injury (retrograde amnesia), nor can he recall the hospital ward where he is told he had conversations with family over the next two days (anterograde amnesia).
The effects of amnesia can last long after the condition has passed; many sufferers claim that amnesia changes from a neurological condition to a psychological condition, whereby the patient loses confidence and faith in their own memory and accounts of past events.
Types and causes of amnesia
Post-traumatic amnesiais generally due to a head injury (e.g. a fall, a knock on the head). Traumatic amnesia is often transient, but may be permanent of either anterograde, retrograde, or mixed type. The extent of the period covered by 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 results 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. The sufferer may also lose knowledge of who people are, they may remember events, but will not remember faces of them.
*Dissociative 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. Dissociative Amnesia can include:
Repressed memoryrefers to the inability to recall information, usually about stressful or traumatic events in persons' lives, such as a violent attack or rape. The memory is stored in long term memory, but access to it is impaired because of psychological defense mechanisms. Persons retain the capacity to learn new information and there may be some later partial or complete recovery of memory. This contrasts with e.g. anterograde amnesia caused by amnestics such as benzodiazepines or alcohol, where an experience was prevented from being transferred from temporary to permanent memory storage: it will never be recovered, because it was never stored in the first place. Formerly known as "Psychogenic Amnesia"
:*Dissociative Fugue ("formerly" Psychogenic Fugue) is also known as fugue state. It is caused by psychological trauma and is usually temporary, unresolved and therefore may return. The
Merck Manualdefines 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." [http://www.merck.com/mrkshared/mmanual/section15/chapter188/188c.jsp The Merck Manuals Online] ] While popular in fiction, it is extremely rare.
:* Posthypnotic amnesia is where events during
hypnosisare forgotten, or where past memories are unable to be recalled.
Lacunar amnesiais the loss of memory about one specific event.
Childhood amnesia(also known as infantile amnesia) is the common inability to remember events from one's own childhood. Sigmund Freudattributed this to sexual repression, while others have theorised that this may be due to language developmentor immature parts of the brain.
Transient global amnesiais a well-described medical and clinical phenomenon. This form of amnesia is distinct in that abnormalities in the hippocampuscan sometimes be visualized using a special form of magnetic resonance imagingof the brain known as diffusion-weighted imaging(DWI). Symptoms typically last for less than a day and there is often no clear precipitating factor nor any other neurological deficits. The cause of this syndrome is not clear, hypotheses include transient reduced blood flow, possible seizure or an atypical type of migraine. Patients are typically amnestic of events more than a few minutes in the past, though immediate recall is usually preserved.
Source amnesiais a memory disorder in which someone can recall certain information, but they do not know where or how they obtained the information.
Memory distrust syndromeis a term invented by the psychologist Gisli Gudjonssonto describe a situation where someone is unable to trust their own memory.
*Blackout phenomenon can be caused by excessive short-term alcohol consumption, with the amnesia being of the anterograde type.
Korsakoff's syndromecan result from long-term alcoholism or malnutrition. It 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. Korsakoff's syndrome is also known to be connected with confabulation.
Drug-induced amnesiais intentionally caused by injection of an amnesiac drug to help a patient forget surgery or medical procedures, particularly those which are not performed under full anesthesia, or which are likely to be particularly traumatic. Such drugs are also referred to as "premedicants". Most commonly a 2'-halogenated benzodiazepinesuch as midazolamor flunitrazepamis the drug of choice, although other strongly amnestic drugs such as propofolor scopolaminemay also be used for this application. Memories of the short time frame in which the procedure was performed are permanently lost or at least substantially reduced, but once the drug wears off, memory is no longer affected.
Amnesia in fiction
Amnesia is prevalent in many works of fiction.
Global amnesiais a common motif in fiction despite being extraordinarily rare in reality. In movies and television, particularly sitcoms and soap operas, it is often depicted that a second hit to the head (similar to the first one) cures the amnesia. Amnesia has also been prominently used as a plot device in many video games to help explain why the main character (and in essence the player) knows very little about the world he is in. In reality, however, repeat concussions may cause cumulative deficits including cognitiveproblems, and in extremely rare cases may even cause deadly swelling of the brain associated with second-impact syndrome.
* Betrayal Trauma
Emotion and memory
* Mr. Nobody
transient epileptic amnesia(TEA)
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amnesia — (n.) loss of memory, 1786 (as a Greek word in English from 1670s), Modern Latin, coined from Gk. amnesia forgetfulness, from a , privative prefix, not + mimneskesthai to recall, cause to remember, a reduplicated form related to Gk. mnemnon… … Etymology dictionary
amnesia — sustantivo femenino 1. (no contable) Área: medicina Pérdida total o parcial de la memoria: La amnesia de mi padre es, de momento, muy selectiva … Diccionario Salamanca de la Lengua Española
amnesia — [am nē′zhə] n. [ModL < Gr amnēsia, forgetfulness < a , not + mnasthai, to remember < IE base * men , *mnā , to think, be alert > MAN, L mens, MIND] partial or total loss of memory caused as by brain injury or by shock amnesiac [am… … English World dictionary
amnesia — am*ne si*a, n. [NL., fr. Gr. amnhsi a; a priv. + mna^sqai to remember.] (Med.) Forgetfulness; also, a defect of speech, from cerebral disease, in which the patient substitutes wrong words or names in the place of those he wishes to employ. Quian … The Collaborative International Dictionary of English
amnésia — s. f. Perda (total ou parcial) da memória … Dicionário da Língua Portuguesa
amnesia — (Del gr. ἀμνησία). f. Pérdida o debilidad notable de la memoria … Diccionario de la lengua española