Anterograde amnesia

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Name of Symptom/Sign:
**Anterograde amnesia**
*Classifications and external resources*
ICD-10	R41.1
ICD-9	780.93

Anterograde amnesia is a form of amnesia, or memory loss, where new events are not transferred to long-term memory. After the onset of the disorder, the sufferer will not be able to recall events which occurred only moments earlier, once their attention has shifted to something else.

1 Symptoms
2 Causes
3 Famous cases
4 Anterograde amnesia in fiction
5 See also
6 External links

[edit] Symptoms

Those who suffer from theoretically pure anterograde amnesia will still be able to recall memories laid down before the onset of anterograde amnesia, but will exist in a transient world where anything beyond their immediate attention-span disappears permanently from their consciousness. In reality, long-term cases of anterograde amnesia are nearly always accompanied by some degree of retrograde amnesia.

This form of amnesia is often referred to as "short-term-memory loss" with the implication that data is lost from the short term memory, such as in the movies Memento and Finding Nemo. However, in technical writing anterograde amnesia is used, since the condition is not a deficit in short-term memory but in long-term encoding.

Different types of memories (e.g., of new physical skills, of new words, of the events of the day, facts of history, etc.) can be separately affected by anterograde amnesia. Patients with anterograde memory loss often can learn and remember a new physical skill (e.g., a musician learning how to play a new tune) and yet not remember when he or she had learned it. Examples have been described where patients learned and remembered new words and facts of history ("semantic" memory) but could not remember any events of their previous day ("episodic" memory).

[edit] Causes

Damage to the hippocampus, fornix, or mammillary bodies can result in anterograde amnesia, which contributes further evidence to the theory that these are the structures primarily responsible for the process of laying down long-term memories. The occurrence of anterograde amnesia can also be due to damage to the Basal Forebrain which produces acetylcholine. The final cause of anterograde amnesia is damage to a set of structures which are located deep in the brain called the diencephalon.

A temporary form of anterograde amnesia, sometimes referred to as traveler's amnesia, is also induced by some medications. Benzodiazepines and imidazopyridines all have varying degrees of anterograde amnesic effects. This is utilised in the use of benzodiazepines such as temazepam and lorazepam as premedicatants. In some cases, for instance, victims may realise they have changed planes during their memory gap or discover that they rented a car.

Large intake of alcohol (see binge drinking) can cause anterograde amnesia commonly referred to as en bloc black outs. This is likely caused by alcohol's effect on GABA receptors, which play a role in memory formation in the hippocampus. [1] Because of the other symptoms of intoxication, it is usually not evident to observers when an intoxicated person is suffering from amnesia, and they themselves will only become aware of it later if they identify a period of missing time. [2]

A more sinister, criminal abuse is in date rape (chemical submission), in which the drugs flunitrazepam, GHB, temazepam, and other common substances are used, unbeknownst to the victim, to produce an uninhibited state, the hallmark of which is anterograde amnesia.

Amnesia automatism is usually induced by prescription drugs, often in association with moderate alcohol intake. Victims have memory gaps for a period shortly after taking the drug concerned, which causes embarrassment and fear for what might have happened. Disinhibited and uncharacteristic behaviour (sometimes together with carrying out quite complex tasks - e.g. cooking and serving a nice meal, but in the nude) is sometimes witnessed during such episodes, which adds further embarrassment and distress. Automatisms involve doing something "automatically" and not remembering afterwards how one did it or even that one did it.

[edit] Famous cases

The most famous case of anterograde amnesia is that of HM or Henry M., the man whose lesions accidentally started the inquiry into the neurobiology of learning and memory.

Clive Wearing was featured in the documentary, The Man with the 7 Second Memory. Wearing fell ill with a herpes simplex virus which attacked his brain. The affected area was the hippocampus, which has a major role in handling memory.

Oliver Sacks characterizes two individuals with anterograde amnesia in his book The Man Who Mistook His Wife for a Hat. Both suffer from Korsakoff's Syndrome, which causes irreversible anterograde amnesia. The story of one patient is called "The Lost Mariner": he began forgetting everything from the end of WWII and felt certain that the date was constantly 1945. He does not even know that he suffers from amnesia and believes himself to be decades younger than he is. The other story is called "A Matter of Identity". Rather than having a consistent false belief about his situation, this patient dealt with his amnesia by constantly re-evaluating and re-explaining his situation. He would greet whoever was in the room over and over again, each time with a different name. Much like "The Lost Mariner", he was unaware of his condition.

Steve Wozniak suffered from anterograde amnesia for approximately five weeks in 1981 following the crash of an ultralight plane he piloted ^{[citation needed]}.

[edit] Anterograde amnesia in fiction

Anterograde amnesia has also been featured in fiction:

The 1985 short story A Clean Escape by John Kessel, in which a psychiatrist torments a man suffering from Korsakov's syndrome. It was adapted into an audio drama for Sci Fi Channel's Seeing Ear Theatre. [3]
In the 1994 comedy Clean Slate, Dana Carvey stars as a man whose anterograde amnesia kicks in whenever he falls asleep (typically once a day).
The November 5, 2003 episode "Twilight" of science fiction TV series Star Trek: Enterprise opens with Captain Archer (Scott Bakula) having unknowingly suffered from anterograde amnesia for 12 years.
The 2004 romantic comedy 50 First Dates casts Adam Sandler as a man who must start anew every day his wooing of anterograde sufferer Drew Barrymore.
The 1940 satire The Great Dictator featured a Jewish barber who suffered from anterograde amnesia, thinking it to be just after the end of WWI, though he recovered early in the film.
The 2000 neo-noir/psychological thriller film Memento, starring Guy Pearce, Carrie-Anne Moss, and Joe Pantoliano, featured Leonard (played by Pearce), a anterograde amnesiac. The film is cut as a series of moments playing backwards, providing the viewer with a kind of 'simulation' as to what anterograde amnesia might be like. Leonard was, as described in the first paragraph under symptoms, a pure anterograde amnesiac. However, he was able to learn about his condition before his onset.
The 2003 animated comedy Finding Nemo features the voice of Ellen DeGeneres as Dory, a regal blue-tang fish with short-term memory loss (for example, she calls Nemo by various names -- Chico, Bingo, Harpo, Fabio -- but when she actually meets Nemo she doesn't remember that's who she's been seeking).
In the renai game Kimi Ga Nozomu Eien and its anime adaptation, one of the main characters, Haruka Suzumiya, suffers from anterograde amnesia after a fateful car accident.
In the 1965 film 36 Hours starring James Garner and Eva Marie Saint, Garner stars as a military planner kidnapped on the eve of the WWII Normandy invasion, and induced to believe he has amnesia in order to reveal the invasion plan.
"The Vintage Book of Amnesia : An Anthology of Writing on the Subject of Memory Loss" Edited by Jonathan Lethem
In Kingdom Hearts II, Oogie Boogie, develops anterograde amnesia after being brought back from the dead by Maleficent. He forgot who brought him back to life after a few cutscenes, and forgets who Santa Claus is and why did he kidnap him despite being ordered by Maleficent to do so.
In the book A Fire Upon the Deep by Vernor Vinge, an entire alien species known as the Skroderiders has no short term memory. These plant-creatures depend on their Skrodes to mobilize them and to aid them in putting things into their long term memory. There are several instances where the reader is treated to scenes of Humans trying to hold conversations with them, with varying degrees of success.
The 2005 Tamil film Ghajini (inspired by Memento), Surya acts as a rich businessman who suffers from amnesia.